Abstracts Archive 2005

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Delayed Defibrillation Testing in Patients Implanted with Biventricular ICD (CRT-D): A Reliable and Safe Approach

Background: Defibrillation testing (DT) at the end of the implantation of cardiac resynchronization pacemaker with a defibrillator (CRT-D) exposes heart failure (HF) patients to increased procedural risks. However, until now, delayed DT has not been assessed as a possible option in HF patients implanted with CRT-D.
Objective: Aim of the present study is to assess safety and feasibility of delayed DT in HF patients treated with CRT-D.
Material and Methods: Two hundred and eleven consecutive patients (mean age: 65 years, mean NYHA class 3.0, mean EF: 29.3%) underwent CRT-D implantation from October 1999 to December 2004. In the first 17 patients, DT was performed at the end of CRT-D implantation. In the other 194 consecutive patients, DT was performed at 2 months after CRT-D implantation. Outcome of DT, as well as "acute" LV lead dislodgment rate were evaluated in the latter group of 194 patients undergoing a delayed DT. Also, ICD function was assessed through device telemetry analysis at 2 months.
Results: At delayed DT, first shock was effective in 187 of 194 patients (96%), ineffective VF interruption at maximum energy occurred only in one patient (0.5%), and acute LV lead dislodgment was 1%. No ICD therapy failure occurred in the 2-month untested period.
Conclusion: DT performed 2 months after CRT-D implantation is safe and feasible; this is possibly related to the improvement of clinical conditions and hemodynamic status as well as greater lead stability 2 months after CRT-D.

 

Atrial overdrive pacing compared to CPAP in patients with obstructive sleep apnoea syndrome

Aims Obstructive sleep apnoea (OSA) is associated with oxygen desaturation, blood pressure increase, and neurohumoral activation, resulting in possible detrimental effects on the cardiovascular system. Continuous positive airway pressure (CPAP) is the therapy of choice for OSA. In a recent study, nocturnal atrial overdrive pacing (pacing) reduced the severity of sleep apnoea in pacemaker patients. We compared the effects of CPAP with those of pacing in patients with OSA but without pacemaker indication or clinical signs of heart failure.
Methods and results Ten patients with OSA on CPAP therapy were studied for three nights by polysomnography. During the nights that followed a night without any treatment (baseline), the patients were treated with CPAP or pacing in a random order. Pacing was performed with a temporary pacing lead. The pacing frequency was 15 b.p.m. higher than the baseline heart rate. The apnoea–hypopnoea index was 41.0 h–1 (12.0–66.6) at baseline and was significantly lower during CPAP [2.2 h–1 (0.3–12.4)] compared with pacing [39.1 h–1 (8.2–78.5)]. Furthermore, duration and quality of sleep were significantly improved during CPAP when compared with pacing.
Conclusion Nocturnal atrial overdrive pacing is no alternative therapeutic strategy to CPAP for the treatment of OSA in patients without clinical signs of heart failure and without conventional indication for antibradycardia pacing.

Ten Year Follow-Up After Radiofrequency Catheter Ablation for Atrioventricular Nodal Reentrant Tachycardia in the Early Days Forever Cured, or a Source for New Arrhythmias?

Background: Radiofrequency (RF) catheter ablation is highly effective with a low complication rate. However, lesions created by RF energy are irreversible, inhomogeneous, and therefore potentially proarrhythmic.
Objectives: The aim of this study was to examine the magnitude and importance of long-term proarrhythmic effects of RF energy.
Methods and Results: Between 1991 and 1995, 120 patients underwent RF ablation for atrioventricular nodal reentrant tachycardia (AVNRT). Patient data were collected by contacting patients and/or filling out a questionnaire, and medical files were screened for recurrent, documented arrhythmias, pharmacological treatment, and repeated EP study. Referring cardiologists were asked about recurrences of tachyarrhythmias. Fourteen patients (11%) were lost to follow-up. During a mean follow-up of 10 years, six patients died. Recurrences of AVNRT were not any more observed after 3 years after ablation. A total of 29 patients (24%) suffered from new arrhythmias, 6 from type 1 atrial flutter, 6 from atrial tachycardia, 9 from atrial fibrillation, and finally 16 from symptomatic premature atrial contractions (PACs), needing medical treatment or a combination of these arrhythmias. Nine patients underwent pacemaker implantation, 4 after developing procedural atrioventricular (AV) conduction disturbances, 2 after His ablation for permanent atrial fibrillation, 1 patient for sick sinus syndrome, and another 2 patients after developing late AV block, respectively, 7 and 9 years after ablation.
Conclusion: During long-term follow-up after RF ablation for AVNRT, no AVNRT recurrences were observed, but 29 patients (24%) suffered from new arrhythmias or late AV block. This potential proarrhythmic effect of RF energy promotes the application of alternative energy sources for ablative therapies for cardiac arrhythmias.
 

Pacemaker stress echocardiography predicts cardiac events in patients with permanent pacemaker

Purpose Noninvasive pacemaker stress echocardiography is a newly introduced method for the diagnosis of coronary artery disease in patients with a permanent pacemaker. The prognostic value of pacemaker stress echocardiography has not been studied.
Subjects and methods We studied 136 patients (mean age 64±12 years) with a permanent pacemaker who underwent pacemaker stress echocardiography for evaluation of coronary artery disease. All patients underwent pacemaker stress echocardiography by external programming (pacing heart rate up to ischemia or target heart rate).
Results Thirty-one patients (23%) had normal study results. Ischemia was detected in 75 patients (55%). During a mean follow-up of 3.5±2.4 years, 35 deaths (26%) (20 the result of cardiac causes) and 2 nonfatal myocardial infarctions (1%) occurred. The annual cardiac death rate was 1.3% in patients without ischemia and 4.6% in patients with ischemia (P=.01). The annual all-cause mortality rate was 3.1% in patients without ischemia and 7% in patients with ischemia (P=.004). The presence of ischemia during pacemaker stress echocardiography was the strongest independent predictor of cardiac death (hazard ratio 4.1, confidence interval 1.2-14.5) and all-cause mortality (hazard ratio 2.7, confidence interval 1.2-6.0) in a multivariable model.
Conclusion Myocardial ischemia during pacemaker stress echocardiography is an independent predictor of cardiac death and all-cause mortality in patients with a permanent pacemaker.
 

Determination of the Optimal Atrioventricular Interval in Sick Sinus Syndrome During DDD Pacing

Background: Although the AAI pacing mode has been shown to be electromechanically superior to the DDD pacing mode in sick sinus syndrome (SSS), there is evidence suggesting that during AAI pacing the presence of natural ventricular activation pattern is not enough for hemodynamic benefit to occur. Myocardial performance index (MPI) is a simply measurable Doppler-derived index of combined systolic and diastolic myocardial performance. The aim of this study was to investigate whether AAI pacing mode is electromechanically superior to the DDD mode in patients with SSS by using Doppler-derived MPI.
Methods: Thirty-nine SSS patients with dual-chamber pacing devices were evaluated by using Doppler echocardiography in AAI mode and DDD mode. The optimal atrioventricular (AV) interval in DDD mode was determined and atrial stimulus-R interval was measured in AAI mode. The ratio of the atrial stimulus-R interval to the optimal AV interval was defined as relative AV interval (rAVI) and the ratio of MPI in AAI mode to that in DDD mode was defined as relative MPI (rMPI).
Results: The rMPI was significantly correlated with atrial stimulus-R interval and rAVI (r = 0.57, P = 0.0002, and r = 0.67, P < 0.0001, respectively). A cutoff point of 1.73 for rAVI provided optimum sensitivity and specificity for rMPI >1 based on the receiver operator curves.
Conclusions: Even though the intrinsic AV conduction is moderately prolonged, some SSS patients with dual-chamber pacing devices benefit from the ventricular pacing with optimal AV interval. MPI is useful to determine the optimal pacing mode in acute experiment.
 

Rapid Decline in Acute Stimulation Thresholds with Steroid-Eluting Active-Fixation Pacing Leads

Background and Aim: There is an increasing use of active-fixation leads for cardiac pacing, yet concerns remain regarding initial high stimulation thresholds. The aim was to perform a detailed analysis of pacing parameters at the time of implantation to determine when lead repositioning should be considered.
Methods: We performed a prospective observational study of consecutive new pacemaker implants. Detailed analysis of pacing parameters was collected at 2-minute intervals for 10 minutes, and at day 1 and week 8 following implant.
Results: Ninety-four patients underwent implantation of 79 dual-chamber and 15 single-chamber pacemakers using active-fixation leads in both chambers. An initial threshold of >1 V was demonstrated in 45/94 (48%) ventricular leads (mean threshold 1.5 ± 0.3 V). This declined rapidly to 0.9 ± 0.3 V at 4 minutes (P < 0.01), 0.7 ± 0.3 V at 10 minutes (P < 0.01), and 0.6 ± 0.3 V at day 1 (P < 0.01). At day 1, 43/45 leads were <1 V. There were 79 atrial leads. An initial threshold of >1 V (mean 1.7 ± 0.6 V) was demonstrated in 41/79 (52%) leads falling significantly to 1.1 ± 0.5 V at 4 minutes (P < 0.01), 0.9 ± 0.4 V at 10 minutes (P < 0.01), and 0.6 ± 0.2 V at day 1 (P < 0.01). At 10 minutes, 32 of 41 leads demonstrated a threshold of <1 V with all leads <1 V at day 1. Thresholds were maintained medium term.
Conclusions: Active-fixation leads are commonly associated with initially high thresholds that fall rapidly. An initial threshold of 2 V should be provisionally accepted and retested at 4 minutes. The majority will have a threshold of <1 V the following day. A failure of a high threshold to decline at 4 minutes requires lead repositioning.
 

Potential proarrhythmic effect of biventricular pacing: Fact or myth?

Background Hemodynamic improvement from biventricular pacing is well documented; however, its electrophysiologic effects have not been systematically studied. Sporadic case reports suggest a proarrhythmic effect of biventricular pacing resulting primarily in polymorphic ventricular tachycardia/ventricular fibrillation (VT/VF).
Objectives The purpose of this study was to report a series of patients in whom implantation of a biventricular system resulted in VT/VF storm with predominance of monomorphic VT.
Methods In a retrospective analysis of all biventricular implants over a 4-year period at a single medical center, we identified 5 of 145 patients (3.4%) who developed VT/VF after they were upgraded to a biventricular system. All patients were male, age 71 ± 8 years, with ejection fraction of 0.25 ± 0.1. Four of five patients had ischemic cardiomyopathy.
Results All patients developed incessant VT/VF within 1 week of implantation. Monomorphic VT of single morphology was noted in 3 of 5 patients, monomorphic VT of multiple morphologies in 1, and polymorphic VT/VF in 1. VT was managed by temporary discontinuation of biventricular pacing in all patients, amiodarone in 3 of 5, sotalol in 1, and beta-blocker in 1. During 11 ± 7 months of follow-up, 4 of 5 patients remain alive and are arrhythmia-free.
Conclusion Biventricular pacing may result in precipitation of VT/VF storm in a minority of patients with prior history of VT/VF. This may be the first case series reporting both monomorphic and polymorphic VT after an upgrade to a system with biventricular pacing capabilities. The arrhythmias can be managed by conventional therapy and may require temporary discontinuation of left ventricular pacing. This observation is relevant to patients receiving a biventricular pacemaker without an implantable cardioverter-defibrillator backup.
 

Atrial Overdrive Pacing for the Obstructive Sleep Apnea–Hypopnea Syndrome

Background The role of atrial overdrive pacing (AOP) in sleep apnea remains uncertain. We prospectively evaluated the effect of AOP after 24 hours and after one month in patients with the obstructive sleep apnea–hypopnea syndrome and compared it with the use of nasal continuous positive airway pressure (n-CPAP).
Methods We studied 16 patients with a moderate or severe case of the obstructive sleep apnea–hypopnea syndrome (baseline mean apnea–hypopnea index, 49) and normal left ventricular systolic function in whom a dual-chamber pacemaker had been implanted. After 48 hours, the patients were randomly assigned to AOP (pacing at 15 bpm above the spontaneous mean nocturnal heart rate) or backup atrial pacing (pacing at a heart rate below 40 bpm); the latter group began n-CPAP therapy one day later. After one month, the two groups switched therapies and were followed for an additional month. Polysomnographic studies were performed at baseline, on the first night after randomization, at crossover, and at the end of the study.
Results During AOP, no significant changes were observed in any of the respiratory variables measured. The change in the apnea–hypopnea index at one month with AOP was +0.2 (95 percent confidence interval, –2.7 to +2.3; P=0.87). In contrast, all variables improved significantly after one month of n-CPAP (change in the apnea–hypopnea index, –46.3; 95 percent confidence interval, –56.2 to –36.5; P<0.001).
Conclusions Nasal continuous positive airway pressure therapy is highly effective for the treatment of the obstructive sleep apnea–hypopnea syndrome, whereas AOP has no significant effect.

Idiopathic fascicular left ventricular tachycardia: Linear ablation lesion strategy for noninducible or nonsustained tachycardia

Background Idiopathic “fascicular” left ventricular tachycardia (IFLVT) is frequently not inducible or nonsustained at the time of planned catheter ablation. The mechanism of the arrhythmia has been suggested to be reentry involving a sizable area of the LV inferior septum extending from base toward the apex.
Objective
We tested the ability of a series of radiofrequency lesions delivered in a linear fashion to the inferior-mid septum to control ventricular tachycardia not amenable to standard mapping ablation strategies.
Methods Programmed stimulation both at baseline state and with isoproterenol after heart rate was increased by at least 25% was performed in all patients. The patients included in the study were either non-inducible or only had brief nonsustained VT not amenable to “traditional” mapping. A detailed electroanatomic map of the LV was performed in sinus rhythm. The location of the linear lesion along the inferior septum was guided by the presence of Purkinje potentials, with pacemapping as an additional guide. A linear lesion was placed perpendicular to the long axis of the ventricle approximately midway from the base to the apex in the region of the mid to mid-inferior septum. Radiofrequency lesions were delivered using a 4mm tip catheter at 50 Watts and 52 degrees for 60–90 seconds.
Results Of 122 consecutive patients who underwent ablation of idiopathic VT from 1999 to 2003, 15 had IFLVT based on standard diagnostic criteria. Six of the 15 patients (40%) had nonsustained or no inducible VT in the EP lab. The number of RF lesions ranged from 7 to 15 (mean 9). The length of the effective linear lesion ranged from 1.2 to 2.2 cm (mean 1.7 cm). Developement of left posterior fascicular block was noted in two of the six patients. However, despite the absence of development of left posterior fascicular block in the other four patients, no VT or premature ventricular beats could be induced after ablation using the same provocation maneuvers as performed in the baseline state. No spontaneous arrhythmias occurred during follow-up to 16 ± 8 months (range 6 to 30 months).
Conclusion In patients with difficult to induce or nonsustained VT with the typical right bundle branch block pattern and a superiorly directed axis on 12-lead ECG, RF energy ablation delivered in a linear fashion approximately midway to two thirds toward the apex along the mid to inferior septum and perpendicular to the plane of the septum is safe and effective for VT control.

Mechanical interruption of postinfarction ventricular tachycardia as a guide for catheter ablation

Background Mechanical trauma has been described as a helpful guide for ablation of atrial tachycardias and accessory pathways. In postinfarction ventricular tachycardia (VT), the reentrant circuit is partly endocardial and therefore may be susceptible to catheter trauma.
Objectives The purpose of this study was to determine the prevalence and significance of VT termination resulting from catheter trauma.
Methods A consecutive series of 39 patients (mean age 68 ± 7 years, ejection fraction 0.25 ± 0.02) underwent left ventricular mapping for postinfarction VT. Mapping was performed during 62 hemodynamically tolerated VTs (mean cycle length 451 ± 88 ms). Only hemodynamically tolerated VTs that did not terminate spontaneously and VTs that were reproducibly inducible were included in the study. VT termination was considered mechanical only if it was not caused by a premature depolarization.
Results In 13 of 62 VTs (21%) in 8 of 39 patients (21%), either VT terminated during catheter placement at a particular site (n = 7) or a previously reproducibly inducible VT became no longer inducible with the mapping catheter located at a particular site (n = 6). The stimulus-QRS interval was significantly shorter at sites where mechanical trauma affected the reentrant circuit compared with sites having concealed entrainment (102 ± 56 ms vs 253 ± 134 ms, P = .003). At the site that was susceptible to mechanical trauma, the pace map was identical or highly similar in 13 of 13 VTs. After radiofrequency ablation at these sites, the targeted VTs were no longer inducible. No patient had recurrence of the targeted VT during a mean follow-up of 15 ± 11 months.
Conclusions Catheter contact at a critical endocardial site can interrupt postinfarction VT or prevent its induction. Radiofrequency ablation at sites of mechanical termination of VT has a high probability of success.

Incidence and predictors of cardiac perforation after permanent pacemaker placement

Background Pericardial effusion, a sign of cardiac perforation, may complicate permanent pacemaker placement. Risk factors for development of post-permanent pacemaker effusion have not been evaluated.
Objectives The purpose of this study was to determine the predictors of symptomatic pericardial effusion after permanent pacemaker placement.
Methods The Mayo Clinic pacemaker and echocardiogram databases were cross-referenced. From 1995 to 2003, 4,280 permanent pacemakers were implanted. Fifty (1.2%) patients developed significant effusion and symptoms consistent with perforation. They were randomly matched with 100 patients without effusion after permanent pacemaker placement.
Results The strongest predictors of postimplant effusion by univariate analysis were the concomitant use of a temporary transvenous pacemaker (hazard ratio [HR] 3.2, 95% confidence interval [CI] 1.6–6.2, P = .001) or steroid use within 7 days prior to implant (HR 4.1, 95% CI 1.1–10, P = .003). Weaker predictors were use of helical screw ventricular leads, body mass index (BMI) <20, older age, and longer fluoroscopy times. Variables associated with lower risk of perforation were right ventricular systolic pressure >35 mmHg (HR 0.70, 95% CI 0.44–0.97, P = .01) or BMI >30 (HR 0.62, 95% CI 0.41–0.93, P = .01). Multivariate predictors were use of temporary pacemaker (HR 2.7, 95% CI 1.4–3.9, P = .01), helical screw leads (HR 2.5; 95% CI 1.4-3.8, P = .04), and steroids (HR 3.2, 95% CI 1.1–5.4, P = .04). Right ventricular systolic pressure >35 mmHg was the only protective factor (HR 0.70, 95% CI 0.50–0.92, P = .02).
Conclusion The incidence of postimplant effusions is low. In order to minimize periprocedural permanent pacemaker effusions, temporary pacemaker placement should be avoided unless essential, and particular care should be taken when placing a permanent pacemaker in patients who are taking steroids.
 

Predictors of appropriate implantable defibrillator therapies in patients with arrhythmogenic right ventricular dysplasia

Background Arrhythmogenic right ventricular dysplasia (ARVD) is an inherited cardiomyopathy characterized by ventricular arrhythmias and sudden cardiac death. The risk factors for sudden death and indications for implantable cardioverter-defibrillator (ICD) placement in patients with ARVD are not well defined.
Objectives The purpose of this study was to determine which clinical and electrophysiologic variables best predict appropriate ICD therapies in patients with ARVD. Particular attention focused on whether the ICD was implanted for primary or second prevention.
Methods We enrolled 67 patients (mean age 36 ± 14 years) with definite or probable ARVD who had undergone ICD placement. Appropriate ICD therapies were recorded, and Kaplan-Meier analysis was used to compare the event-free survival time between patients based upon the indication for ICD placement (primary vs secondary prevention), results of electrophysiologic testing, and whether the patient had probable or definite ARVD.
Results Over a mean follow-up of 4.4 ± 2.9 years, 40 (73%) of 55 patients who met task force criteria for ARVD and 4 (33%) of 12 patients with probable ARVD had appropriate ICD therapies for ventricular tachycardia/ventricular fibrillation (VT/VF; P = .027). Mean time to ICD therapy was 1.1 ± 1.4 years. Eleven of 28 patients who received an ICD for primary prevention (39%) and 33 of 35 patients who received an ICD for secondary prevention (85%) experienced appropriate ICD therapies (P = .001). Electrophysiologic testing did not predict appropriate ICD interventions in patients who received an ICD for primary prevention. Fourteen patients (21%) received ICD therapy for life-threatening (VT/VF >240 bpm) arrhythmias. There was no difference in the incidence of life-threatening arrhythmias in the primary and secondary prevention groups (P = .29).
Conclusion Patients who meet task force criteria for ARVD are at high risk for sudden cardiac death and should undergo ICD placement for primary and secondary prevention, regardless of electrophysiologic testing results. Further research is needed to confirm that a low-risk subset of patients who may not require ICD placement can be identified.
 

Automatic measurement of atrial pacing thresholds in dual-chamber pacemakers: Clinical experience with atrial capture management

Background The Medtronic EnPulse™ pacemaker incorporates the new atrial capture management (ACM) algorithm to automatically measure atrial capture thresholds and subsequently manage atrial pacing outputs.
Objectives The purpose of this study was to evaluate the clinical performance of ACM.
Methods Two hundred patients with an indication for a dual-chamber pacemaker underwent implantation. ACM thresholds and manually measured atrial pacing thresholds were assessed at follow-up visits. Clinical equivalence was defined as the ACM-measured threshold being within −0.25 V to +0.5 V of the manually measured threshold. The clinician analyzed all ACM measurements performed in-office for evidence of proarrhythmia.
Results All 200 implanted patients had a 1-month visit, and validated manual and in-office ACM threshold data were available for 123 patients. The ACM threshold was 0.595 ± 0.252 V, and the manual threshold was 0.584 ± 0.233 V. The mean difference was 0.010 V with a 95% confidence interval of (−0.001, 0.021). The mean difference over all visits was 0.011 V. For all patients, the individual threshold differences were within the range of clinical equivalence at all visits. No atrial arrhythmias were observed during 892 ACM tests in 193 patients.
Conclusion This study demonstrated that the ACM algorithm is safe, accurate, and reliable over time. ACM was demonstrated to be clinically equivalent to the manual atrial threshold test in all patients at 1 month and over the entire follow-up period of up to 6 months. ACM ensures atrial capture, may save time during follow-up, and can be used to manage atrial pacing outputs.
 

Inaccurate electrocardiographic interpretation of long QT: The majority of physicians cannot recognize a long QT when they see one

Background Physicians in all fields of medicine may encounter patients with long QT syndrome (LQTS). It is important to define the percentage of physicians capable of distinguishing QT intervals that are long from those that are normal because LQTS can be lethal when left untreated.
Objectives The purpose of this study was to define the percentage of physicians in the different disciplines of medicine who can recognize a long QT when they see one.
Methods We presented the ECGs of two patients with LQTS and two healthy females to 902 physicians (25 world-renowned QT experts, 106 arrhythmia specialists, 329 cardiologists, and 442 noncardiologists) from 12 countries. They were asked to measure the QT, calculate the QTc (the QT interval corrected for the heart rate), and determine whether the QT is normal or prolonged.
Results For patients with LQTS, >80% of arrhythmia experts but <50% of cardiologists and <40% of noncardiologists calculated the QTc correctly. Underestimation of the QTc of patients with LQTS and overestimation of the QTc of healthy patients were common. Interobserver agreement was excellent among QT experts, moderate among arrhythmia experts, and low among cardiologists and noncardiologists (kappa coefficient = 0.82, 0.44, and < 0.3, respectively). Correct classification of all QT intervals as either “long” or “normal” was achieved by 96% of QT experts and 62% of arrhythmia experts, but by only <25% of cardiologists and noncardiologists.
Conclusions Most physicians, including many cardiologists, cannot accurately calculate a QTc and cannot correctly identify a long QT.
 

Extent of myocardial viability predicts response to biventricular pacing in ischemic cardiomyopathy

Background The clinical response to biventricular pacing is unpredictable, especially in patients with ischemic cardiomyopathy.
Objectives The purpose of this study was to prospectively examine the relationship between the extent of myocardial viability and the response to cardiac resynchronization therapy.
Methods Twenty-one patients with ischemic left ventricular (LV) dysfunction (left ventricular ejection fraction [LVEF] 21 ± 5%), New York Heart Association (NYHA) functional class III–IV, and QRS >120 ms received biventricular devices. Myocardial viability was assessed by myocardial contrast echocardiography, and a perfusion score index (PSI) was calculated from summed segmental perfusion scores. LV performance was assessed by echocardiography on the day after implantation and at 6 months.
Results PSI was closely correlated with acute improvement in LVEF (P = .003, r = 0.65), stroke volume (P = .02, r = 0.54), and end-systolic volume (P = .05, r = −0.49). PSI also correlated with early diastolic LV relaxation (E′, P < .05, r = 0.50) and global myocardial performance or Tei index (P = .003, r = 0.63). By multiple linear regression analysis, PSI provided incremental predictive value to the degree of dyssynchrony, measured by tissue Doppler imaging, for predicting improvement in LVEF. At 6 months, PSI remained positively correlated with improvement in ventricular performance and with reduction in LV end-diastolic dimension (P = .003, r = −0.68). PSI also influenced the clinical variables of NYHA class, 6-minute walk distance, quality-of-life score, and number of hospitalizations for heart failure.
Conclusion In patients with ischemic cardiomyopathy, the extent of myocardial viability predicts acute and long-term improvement in LV performance, exercise tolerance, and reduction in LV end-diastolic dimension with biventricular pacing.
 

Cardiac resynchronization therapy in patients with right bundle branch block: Analysis of pooled data from the MIRACLE and Contak CD trials

Objectives We pooled data from two randomized controlled trials of CRT (Multicenter InSync Randomized Clinical Evaluation [MIRACLE] and Contak CD) in order to assess outcomes of patients with RBBB.
Methods A total of 61 patients with RBBB were identified, 34 of whom were randomized to the CRT group and 27 to the control group. The data from these patients were entered into a new database and analyzed.
Results Baseline demographics were not different between the two groups (mean age 65.5 ± 11.3 years vs 69.5 ± 9.6 years; male gender 91% vs 85%; patients with coronary disease 76.5% vs 88%; QRS duration 167 ms vs 164 ms; all P = NS). Outcome variables (New York Heart Association [NYHA] class, 6-minute hall walk distance, peak oxygen consumption (VO2), Minnesota Living with Heart Failure quality-of-life scores, left ventricular ejection fraction, and norepinephrine levels) were analyzed at randomization, 3 months, and 6 months.
Conclusions (1) With the exception of NYHA class, patients with RBBB as the qualifying wide QRS did not derive significant benefit from CRT in any of the other parameters studied at 3 or 6 months. (2) RBBB patients who received active CRT showed significant improvements in NYHA class by 6 months and trends toward improvement in 6-minute walk distance, quality-of-life scores, and norepinephrine levels. However, control patients also showed significant improvement in NYHA class by 6 months but showed no improvement in objective measurements (VO2, 6-minute walk distance, left ventricular ejection fraction, and norepinephrine levels), consistent with a placebo effect. Analysis of a larger cohort of patients with RBBB undergoing CRT may demonstrate significant benefit, but the current analysis does not support the use of CRT in patients with RBBB.

Prolonged Paced QRS Duration as a Predictor for Congestive Heart Failure in Patients with Right Ventricular Apical Pacing

Background: The recent studies showed that right ventricular (RV) pacing was associated with worsening of heart failure. The aim of this study is to clarify the clinical significance of paced QRS duration during RV pacing to predict congestive heart failure (CHF) patients.
Methods and Results: This study enrolled in 92 patients with atrioventricular block who underwent initial pacemaker implantation. The paced QRS duration was automatically obtained by electrocardiography immediately after pacemaker implantation and then by routine attendance at a pacemaker clinic every 3 months. The paced QRS duration was positively correlated with left ventricular end-diastolic dimension (P < 0.05) and left ventricular end-systolic dimension (P < 0.05), and tended to negatively correlate with left ventricular ejection fraction (P = 0.0507). The paced QRS duration immediately after pacemaker implantation was 170.4 ± 18.9 ms. During a mean follow-up period of 53 ± 16 months, 16 patients developed CHF. We selected as a cut-off value the nearest whole number (190 ms) that was one standard deviation greater than the mean, and divided into two groups according to baseline paced QRS duration. Patients with a paced QRS duration of <190 ms comprised group A (n = 77, nine of which developed CHF) and the remainder comprised group B (n = 15, seven of which developed CHF). Prolonged paced QRS duration (≥190 ms) was associated with a significant increase in the overall morbidity of CHF (P < 0.05). Additionally, paced QRS duration significantly prolonged during the follow-up period among group A patients with CHF (P < 0.05), but did not change among patients without CHF.
Conclusion: We concluded that paced QRS duration can be a useful indicator of impaired left ventricular function in patients with RV pacing. Even in patients whose paced QRS duration is relatively shorter, progressive prolongation of paced QRS duration can predict the development of CHF.
 

Long-Term Mortality in Patients with Pauses in Ventricular Electrical Activity

Background: The long-term significance of ventricular pauses of ≥3.0 seconds observed on Holter monitor is unclear, as previously conducted retrospective studies have been poorly controlled. We compared the prognosis of patients with pauses ≥3.0 seconds on Holter monitor with a well-matched control group without such pauses.
Methods: Scanning the Holter database at Ochsner Clinic (n = 11,730; January 1998 to June 2003) for pauses ≥3.0 seconds identified 70 patients (pause group). Of those, 29 (37.1%) received a permanent pacemaker (PPM group) and 41 (62.9%) did not (No-PPM group). For each No-PPM patient, two patients without pauses (<2.0 seconds) exactly matched for age, sex, ejection fraction (EF), rhythm, and duration of follow-up were randomly chosen from the Holter database (control group, n = 82) and survival of the two groups was compared.
Results: Mean age was 72.5 ± 15.0 years, mean EF was 52.2 ± 12.7%, and 68.3% were men. Mean follow-up was 2.2 years (0.5–4.5 years). There was no difference in survival between the No-PPM and the control groups (82.9% vs 84.1%, P = NS). Compared with the PPM group, pauses in the No-PPM group were more commonly asymptomatic, nocturnal, and due to sinus pauses or atrial fibrillation (AF) with slow ventricular response.
Conclusions: Pauses in ventricular electrical activity ≥3 seconds on Holter monitor due to sinus pauses or AF with slow ventricular response are not predictive of heightened mortality.
 

The Effect of Losartan Versus Atenolol on Cardiovascular Morbidity and Mortality in Patients With Hypertension Taking Aspirin: The Losartan Intervention for Endpoint Reduction in Hypertension (LIFE) Study

BACKGROUND: Negative interactions between angiotensin-converting enzyme inhibitors and aspirin have been reported. There are no data reported from clinical trials about possible interactions between angiotensin-II receptor antagonists and aspirin.
METHODS: The LIFE study assigned 9,193 patients with hypertension and left ventricular hypertrophy (LVH) to losartan- or atenolol-based therapy for a mean of 4.7 years, with 1,970 (21.4%) taking aspirin at baseline. The primary composite end point (CEP) included cardiovascular death, stroke, and myocardial infarction (MI). The present cohort was stratified by aspirin use at baseline.
RESULTS: Blood pressures were reduced similarly in the losartan with aspirin (n = 1,004) and atenolol with aspirin (n = 966) groups. The CEP was reduced by 32% (95% confidence interval 0.55 to 0.86, p = 0.001) with losartan with aspirin compared to atenolol with aspirin, adjusted for Framingham risk score and LVH. The test for treatment versus aspirin interaction, excluding other covariates, was significant for the CEP (p = 0.016) and MI (p = 0.037).
CONCLUSIONS: There was a statistical interaction between treatment and aspirin in the LIFE study, with significantly greater reductions for the CEP and MI with losartan in patients using aspirin than in patients not using aspirin at baseline. Further studies are needed to clarify whether this represents a pharmacologic interaction or a selection by aspirin use of patients more likely to respond to losartan treatment.
 

Junctional Rhythm—A Suitable Surrogate Endpoint in Catheter Ablation of Atrioventricular Nodal Reentry Tachycardia?

Introduction: Current AHA/ACC guidelines state that junctional rhythm (JR) is an acceptable endpoint in patients undergoing radiofrequency ablation (RFA) for narrow complex tachycardia in the presence of dual AV nodal physiology, but in the absence of inducible AVNRT. Only limited data are available on the utility of JR as a marker of successful slow pathway ablation. We sought to further characterize the sensitivity, specificity, and predictive value of JR in AVNRT ablation.
Methods: A retrospective analysis was performed of 387 consecutive patients with documented narrow complex tachycardia referred for ablation, with dual AV nodal physiology and inducible AVNRT at electrophysiological study. RFA of slow pathway was performed, with the presence or absence of JR recorded for each application and inducibility tested using atrial stimulation protocol and isoproterenol.
Results: Successful ablation was achieved in 385 of 387 patients using a total of 1,861 applications of radiofrequency energy. JR occurred in 692 applications, giving a sensitivity and specificity of JR as an indicator of successful ablation of 99.5% and 79.1% and a positive predictive value of 55.5%.
Conclusions: This study confirms that successful ablation of slow pathway seldom occurs in the absence of JR. Although JR almost invariably occurs with successful ablation, its lack of specificity and low positive predictive value questions the use of it as an endpoint in AVNRT ablations, and the guidelines should reflect this.
 

Off-Pump Coronary Artery Surgery for Reducing Mortality and Morbidity Meta-Analysis of Randomized and Observational Studies

OBJECTIVES: The purpose of this study was to assess the effects of off-pump coronary bypass surgery (OPCAB) on mortality and morbidity.
BACKGROUND: Despite its potential for reducing morbidity and mortality, OPCAB’s role in clinical practice remains controversial.
METHODS: A meta-analysis of 37 randomized controlled trials (RCTs) (n=3,449) and 22 risk-adjusted (logistic regression or propensity-score) observational studies (n=293,617) was performed. Two reviewers performed literature searches (MEDLINE, EMBASE, PubMed, reference lists), quality assessment, and data extraction. Treatment effects were calculated as odds ratios (ORs) with 95% confidence intervals (CIs).
RESULTS: In RCTs, OPCAB was associated with reduced atrial fibrillation (OR 0.59; 95% CI 0.46 to 0.77) and trends toward reduced 30-day mortality (OR 0.91 95% CI 0.45 to 1.83), stroke (OR 0.52; 95% CI 0.25 to 1.05), and myocardial infarction (OR 0.79; 95% CI 0.50 to 1.25). Observational studies showed OPCAB to be associated with reduced 30-day mortality (OR 0.72; 95% CI 0.66 to 0.78), stroke (OR 0.62; 95% CI 0.55 to 0.69), infarction (OR 0.66; 95% CI 0.50 to 0.88), and atrial fibrillation (OR 0.78; 95% CI 0.74 to 0.82). At one to two years, OPCAB was associated with trends toward reduced mortality, but also increased repeat revascularization (RCT: OR 1.75, 95% CI 0.78 to 3.94; Observational: OR 1.35, 95% CI 0.76 to 2.39).
CONCLUSIONS: Randomized controlled trials did not find, aside from atrial fibrillation, the statistically significant reductions in short-term mortality and morbidity demonstrated by observational studies. These discrepancies might be due to differing patient-selection and study methodology. Future studies must focus on improving research methodology, recruiting high-risk patients, and collecting long-term data.
 

Eplerenone Reduces Mortality 30 Days After Randomization Following Acute Myocardial Infarction in Patients With Left Ventricular Systolic Dysfunction and Heart Failure

OBJECTIVES: This study sought to assess the impact of the selective aldosterone blocker eplerenone on mortality 30 days after randomization in patients after acute myocardial infarction (AMI) with a left ventricular ejection fraction (LVEF) 40% and clinical signs of heart failure.
BACKGROUND: In the Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study (EPHESUS), eplerenone reduced all-cause mortality by 15% (p = 0.008) over a mean follow-up of 16 months when used with standard therapy in patients after AMI with an LVEF 40% and clinical signs of heart failure.
METHODS: We analyzed the effect of eplerenone 25 mg/day initiated 3 to 14 days after AMI (mean, 7.3 days) on the co-primary end points of time to death from any cause and the composite end point of time to death from cardiovascular (CV) causes or hospitalization for CV events, and the secondary end points of CV mortality, sudden cardiac death, and fatal/nonfatal hospitalization for heart failure, after 30 days of therapy in the EPHESUS trial.
RESULTS: At 30 days after randomization, eplerenone reduced the risk of all-cause mortality by 31% (3.2% vs. 4.6% in eplerenone and placebo-treated patients, respectively; p = 0.004) and reduced the risk of CV mortality/CV hospitalization by 13% (8.6% vs. 9.9% in eplerenone and placebo-treated patients, respectively; p = 0.074). Eplerenone also reduced the risk of CV mortality by 32% (p = 0.003) and the risk of sudden cardiac death by 37% (p = 0.051).
CONCLUSIONS: Eplerenone 25 mg/day significantly reduced all-cause mortality 30 days after randomization (when initiated at a mean of 7.3 days after AMI) in addition to conventional therapy in patients with an LVEF 40% and signs of heart failure. Based on its early survival benefit, eplerenone should be administered in the hospital after AMI.
 

Prolongation of the fast pathway effective refractory period during cryoablation in children: A marker of slow pathway modification

Objectives Using the unique features of cryotherapy, this study assesses the short-term changes in fast pathway ERP during cryomodification of the slow pathway and examines whether these changes are a useful marker for successful slow pathway modification in children.
Methods Nineteen pediatric patients (median age 15.1 years, range 9.6–19.6 years; weight 60.7 kg, range 35.6–130.2 kg) with anterograde dual AV nodal physiology underwent slow pathway modification with catheter-based cryoablation. Programmed stimulation was performed during cryoapplications after reaching −25°C to assess fast pathway and slow pathway conduction. Data were analyzed from 59 of 237 cryoapplications where the fast pathway ERP was measured more than once (n = 13 patients).
Results For 23 of 59 applications where the slow pathway was modified, the fast pathway ERP significantly increased during cryotherapy (Δ = 33.5 ms, P <.0001). The magnitude of fast pathway ERP prolongation during cryotherapy was larger when the slow pathway was modified than when there was no effect on slow pathway conduction (33.5 ± 30.5 vs 5.8 ± 18.9 ms, P =.0005). Prolongation of fast pathway ERP by ≥20 ms had 70% sensitivity and 72% specificity for predicting slow pathway modification. Following termination of cryoapplications, which resulted in slow pathway modification, the fast pathway ERP had significantly decreased from baseline (difference 44.5 ms, P <.0001). The effect on fast pathway ERP was not related to changes in cycle length during (R2 = 0.04, P = .045) or after ablation (R2 = 0.13, P = .012).
Conclusion The fast pathway ERP prolongs during cryoapplications that result in slow pathway modification and shortens after termination of cryoapplications. The magnitude of fast pathway ERP prolongation during cryoapplication may be useful as a marker for successful slow pathway modification.
 

Left Ventricular-Based Cardiac Stimulation Post AV Nodal Ablation Evaluation (The PAVE Study)

Background: Chronic right ventricular pacing has been reported to promote cardiac dyssynchrony. The PAVE trial prospectively compared chronic biventricular pacing to right ventricular pacing in patients undergoing ablation of the AV node for management of atrial fibrillation with rapid ventricular rates.
Methods and Results: One hundred and eighty-four patients requiring AV node ablation were randomized to receive a biventricular pacing system (n = 103) or a right ventricular pacing system (n = 81). The study endpoints were change in the 6-minute hallway walk test, quality of life, and left ventricular ejection fraction. Patient characteristics were similar (64% male; age: 69 ± 10 years, ejection fraction: 0.46 ± 0.16; 83%, NYHA Class II or III). At 6 months postablation, patients treated with cardiac resynchronization had a significant improvement in 6-minute walk distance, (31%) above baseline (82.9 ± 94.7 m), compared to patients receiving right ventricular pacing, (24%) above baseline (61.2 ± 90.0 m) (P = 0.04). There were no significant differences in the quality-of-life parameters. At 6 months postablation, the ejection fraction in the biventricular group (0.46 ± 0.13) was significantly greater in comparison to patients receiving right ventricular pacing (0.41 ± 0.13, P = 0.03). Patients with an ejection fraction ≤45% or with NYHA Class II/III symptoms receiving a biventricular pacemaker appear to have a greater improvement in 6-minute walk distance compared to patients with normal systolic function or Class I symptoms.
Conclusion: For patients undergoing AV node ablation for atrial fibrillation, biventricular pacing provides a significant improvement in the 6-minute hallway walk test and ejection fraction compared to right ventricular pacing. These beneficial effects of cardiac resynchronization appear to be greater in patients with impaired systolic function or with symptomatic heart failure.
 

Factors Influencing Appropriate Firing of the Implanted Defibrillator for Ventricular Tachycardia/Fibrillation. Findings From the Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II)

OBJECTIVES: The purpose of this study was to prospectively examine the role of clinical, laboratory, echocardiographic, and electrophysiological variables as predictors of appropriate initial implantable cardioverter-defibrillator (ICD) therapy for ventricular tachycardia (VT) or ventricular fibrillation (VF) or death in the Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II) population.
BACKGROUND: There is limited information regarding the determinants of appropriate ICD therapy in patients with reduced ventricular function after a myocardial infarction.
METHODS: We used secondary analysis in one arm of a multicenter randomized clinical trial in patients with a previous myocardial infarction and reduced left ventricular function.
RESULTS: We analyzed baseline and follow-up data on 719 patients enrolled in the ICD arm of the MADIT-II study. Appropriate ICD therapy was observed in 169 subjects. Clinical, laboratory, echocardiographic, and electrophysiological variables, along with measures of clinical instability such as interim hospitalization for congestive heart failure (IH-CHF) and interim hospitalization for coronary events (IH-CE), were examined with proportional hazards models and Kaplan-Meier time-to-event curves before and after first interim hospitalization. Interim hospitalization-CHF, IH-CE, no beta-blockers, digitalis use, blood urea nitrogen (BUN) >25, body mass index (BMI) 30 kg/m2, and New York Heart Association functional class >II were associated with increased risk for appropriate ICD therapy for VT, VF, or death. In a multivariate (stepwise selection) analysis, IH-CHF was associated with an increased risk for the end point of either VT or VF (hazard ratio [HR] 2.52, 95% confidence interval [CI] 1.69 to 3.74, p < 0.001) and for the combined end point of VT, VF, or death (HR 2.97, 95% CI 2.15 to 4.09, p < 0.001). Interim hospitalization-CE was associated with an increased risk for VT, VF, or death (HR 1.66, 95% CI 1.09 to 2.52, p = 0.02).
CONCLUSIONS: These results provide important mechanistic information, suggesting that worsening clinical condition and cardiac instability, as reflected by an IH-CHF or IH-CE, are subsequently associated with a significant increase in the risk for appropriate ICD therapy (for VT/VF) and death.
 

Catheter Ablation of Long-Lasting Persistent Atrial Fibrillation: Critical Structures for Termination

Background: The relative contributions of different atrial regions to the maintenance of persistent atrial fibrillation (AF) are not known.
Methods: Sixty patients (53 ± 9 years) undergoing catheter ablation of persistent AF (17 ± 27 months) were studied. Ablation was performed in a randomized sequence at different left atrial (LA) regions and comprised isolation of the pulmonary veins (PV), isolation of other thoracic veins, and atrial tissue ablation targeting all regions with rapid or heterogeneous activation or guided by activation mapping. Finally, linear ablation at the roof and mitral isthmus was performed if sinus rhythm was not restored after addressing the above-mentioned areas. The impact of ablation was evaluated by the effect on the fibrillatory cycle length in the coronary sinus and appendages at each step. Activation mapping and entrainment maneuvers were used to define the mechanisms and locations of intermediate focal or macroreentrant atrial tachycardias.
Results: AF terminated in 52 patients (87%), directly to sinus rhythm in 7 or via the ablation of 1–6 intermediate atrial tachycardias (total 87) in 45 patients. This conversion was preceded by prolongation of fibrillatory cycle length by 39 ± 9 msec, with the greatest magnitude occurring during ablation at the anterior LA, coronary sinus and PV-LA junction. Thirty-eight atrial tachycardias were focal (originating dominantly from these same sites), while 49 were macroreentrant (involving the mitral or cavotricuspid isthmus or LA roof). Patients without AF termination displayed shorter fibrillatory cycles at baseline: 130 ± 14 vs 156 ± 23 msec; P = 0.002.
Conclusion: Termination of persistent AF can be achieved in 87% of patients by catheter ablation. Ablation of the structures annexed to the left atrium—the left atrial appendage, coronary sinus, and PVs—have the greatest impact on the prolongation of AF cycle length, the conversion of AF to atrial tachycardia, and the termination of focal atrial tachycardias.
 

Chronic Hemodynamic Effects After Radiofrequency Catheter Ablation of Frequent Monomorphic Ventricular Premature Beats

Introduction: Radiofrequency catheter ablation (RFCA) of severely symptomatic monomorphic ventricular premature beats (VPBs) is reported to be a safe and effective treatment option. However, the chronic hemodynamic effects of these VPBs have not been precisely evaluated.
Methods and Results: We sought to investigate chronic effects after decreasing the number of VPBs by RFCA. A total of 47 patients who had no underlying heart disease and frequent monomorphic VPBs, consisting of more than 10,000 beats per day (24,194 ± 12,516 beats per day), were enrolled. Patients were treated with RFCA and followed up over 6 months as outpatients. Echocardiography and serum B-type natriuretic peptide (BNP) level were repeatedly checked before and after RFCA. In 38 patients, whose VPBs were dramatically decreased to less than 1,000 beats per day by successful RFCA, left ventricular (LV) end-diastolic dimension (LVEDd) and end-systolic dimension (LVESd) measured by echocardiography decreased significantly (LVEDd: 50 ± 5 to 48 ± 5 mm, P < 0.01; LVESd: 33 ± 7 to 30 ± 6 mm, P < 0.01) in association with improvement of BNP level (39.9 ± 34.1 to 16.8 ± 10.3 pg/mL, P = 0.0001). In nine patients, whose VPBs were treated unsuccessfully by RFCA or that recurred, LV dimensions and BNP level did not change during the follow-up period.
Conclusion: Significant improvement in LV dimensions and serum BNP level appeared to indicate that RFCA of VPBs ameliorated occult cardiac dysfunction induced by frequent VPBs.
 

“Cardioneuroablation” – new treatment for neurocardiogenic syncope, functional AV block and sinus dysfunction using catheter RF-ablation

Cardiac neuroablation is a new technique for management of patients with dominantly adverse parasympathetic autonomic influence. The technique is based on radiofrequency (RF) ablation of autonomic connections in the three main ganglia around the heart. Their connections are identified by Fast-Fourier Transforms (FFTs) of endocardial signals: sites of autonomic nervous connections show fractionated signals with FFTs shifted to the right. In contrast, normal myocardium without these connections does not show these features. RF-ablation is thought to inflict permanent damage on the parasympathetic autonomic influence because its cells are adjacent to the heart whereas sympathetic cells are remote. Twenty-one patients with a mean age of 48 years, neurally mediated reflex syncope in six, functional high grade atrioventricular block in seven and sinus node dysfunction in 13 (there is overlap between the second and third groups) were treated. Follow-up for a mean of 9.2 months demonstrated success in all cases with relief of symptoms. No complications occurred.
 

Atrial pacing and sensing characteristics in heart failure patients undergoing cardiac resynchronization therapy

Patients with heart failure and sinus rhythm undergoing cardiac resynchronization therapy (CRT) require the proper detection of atrial signals and reliable atrial pacing for AV-synchronous ventricular pacing. The study aim was to compare atrial pacing and sensing characteristics in patients with transvenous CRT and patients with standard pacing indications.
Methods The study group consisted of 31 heart failure patients with depressed left ventricular function and bundle branch block, and the control group of 124 patients with dual-chamber pacemakers because of standard pacing indications. The bipolar steroid-eluting atrial screw-in lead Tendril DX 1388 T (St. Jude Medical) was implanted and connected to pulse generators that provide similar diagnostic features. The unipolar pacing threshold at 0.4ms duration, bipolar sensing threshold, and unipolar pacing impedance were determined at implantation and after 1, 3, and 6 months.
Results At implantation, the atrial pacing threshold was significantly higher in the CRT group than in the control group, 1.07±0.99V versus 0.74±0.36V (P<0.01). Similar pacing thresholds were recorded after 1 month. The pacing threshold in the CRT group was significantly higher at 1.46±0.92V after 3 and 1.50±0.94V after 6 months (control group: 0.96±0.25V at month 3; 0.98±0.32V at month 6; P<0.05). Sensing threshold was similar at implantation with 2.36±1.87mV in the CRT and 2.54±0.78mV in the control group. The sensing threshold in the CRT group decreased to 1.64±0.86mV after 3 and to 1.71±0.71mV after 6 months and was significantly lower compared with the control group (2.16±0.57mV at month 3; 2.27±0.98mV at month 6; P<0.05). At implant, the atrial pacing impedance was not different between the two groups with 443±156ohms in the CRT and 416±116ohms in the control group. During follow-up, the impedance became significantly lower in the CRT group compared with the control group (404±84ohms versus 452±101ohms at month 3; P<0.05).
Conclusions Compared with patients with standard pacing indications, CRT recipients have less good electrical characteristics in the atrium. Atrial pacing and sensing function should be closely monitored in CRT patients.
 

What is the “Optimal” follow-up schedule for ICD patients?

Background In the absence of comparative studies, recommended routine follow-up (FU) intervals for implantable cardioverter defibrillator (ICD) patients range from 1 to 6 months; most patients are followed at 3 month intervals.
Methods Six hundred and eighteen ICD patients were routinely seen 4 weeks after implant and then every 3 months. Unplanned visits (UPV) were either patient initiated or due to manufacturer recalls. FU visits included patient history/examination, ICD interrogation, pacing/sensing threshold and pacing/shock impedance. Chest X-rays were performed every 6 months. To validate FU interval recommendations, a comparative analysis on the detection of complications was performed, relying either on the information of every, or of every other FU visit, i.e., on 3 or 6 month intervals.
Results During 3.3±2.8 years, 137 complications occurred in 110 patients (17%). However, identification of only 34% was dependent on the FU schedule, since the mode of detection was ICD interrogation in 38 and history/physical examination in nine patients. The remainder was diagnosed by UPV in 47, manufacturer recall in seven, accidental discovery during device replacement in two, and routine X-ray in 34 patients. Complication free survival at 2 years was 86.4% for patients implanted before 1999, and 89.2% thereafter (P=0.003). Regarding 6 rather than 3 month FU intervals, a theoretical maximum delay of 3 months in the detection of potentially life-threatening complications would have occurred in 1.7% of all patients. For those implanted after 1999, this related to only 0.9%.
Conclusions ICD-related complications detected during routine FU visits are relatively rare, particularly with newer generation ICD systems. Thus, 6 month FU intervals appear to be safe. With new developments such as patient alert features and telemedical data transmission, FU intervals in ICD clinics might even be further extended.
 

Malignant Entity of Idiopathic Ventricular Fibrillation and Polymorphic Ventricular Tachycardia Initiated by Premature Extrasystoles Originating From the Right Ventricular Outflow Tract

OBJECTIVES: The aim of this study was to assess the clinical characteristics and the efficacy of radiofrequency catheter ablation (RFCA) for idiopathic ventricular fibrillation (VF) and/or polymorphic ventricular tachycardia initiated by ventricular extrasystoles originating from the right ventricular outflow tract (RVOT).
BACKGROUND: Ventricular fibrillation and/or polymorphic ventricular tachycardia are occasionally initiated by ventricular extrasystoles originating from the RVOT in patients without structural heart disease.
METHODS: Among 101 patients without structural heart disease in whom RFCA was conducted for idiopathic ventricular tachyarrhythmias arising from the RVOT, we examined the clinical characteristics and the efficacy of RFCA in 16 patients with spontaneous VF and/or polymorphic ventricular tachycardia initiated by the ventricular extrasystoles originating from the RVOT.
RESULTS: Among 16 patients, spontaneous episodes of VF were documented in 5 patients, and 11 patients had prior episodes of syncope. Holter recordings showed frequent isolated ventricular extrasystoles with the same morphology as that of initiating ventricular extrasystoles, and non-sustained polymorphic ventricular tachycardia with short cycle length (mean of 245 ± 28 ms) in all 16 patients. Radiofrequency catheter ablation by targeting the initiating ventricular extrasystoles eliminated episodes of syncope, VF, and cardiac arrest in all patients during follow-up periods of 54 ± 39 months.
CONCLUSIONS: Our data suggest that the malignant entity of idiopathic VF and/or polymorphic ventricular tachycardia was occasionally present in patients with idiopathic ventricular arrhythmias arising from the RVOT. Radiofrequency catheter ablation was effective as a treatment option for this entity.
 

Diagnosis of Unexplained Cardiac Arrest. Role of Adrenaline and Procainamide Infusion

Background--Cardiac arrest with preserved left ventricular function may be caused by uncommon genetic conditions. Although these may be evident on the ECG, long-term monitoring or provocative testing is often necessary to unmask latent primary electrical disease.
Methods and Results--Patients with unexplained cardiac arrest and no evident cardiac disease (normal left ventricular function, coronary arteries, and resting corrected QT) underwent pharmacological challenge with adrenaline and procainamide infusions to unmask subclinical primary electrical disease. Family members underwent noninvasive screening and directed provocative testing on the basis of findings in the proband. Eighteen patients (mean±SD age, 41±17 years; 11 female) with unexplained cardiac arrest were assessed. The final diagnosis was catecholaminergic ventricular tachycardia (CPVT) in 10 patients (56%), Brugada syndrome in 2 patients (11%), and unexplained (idiopathic ventricular fibrillation) in 6 patients (33%). Of 55 family members (mean±SD age, 27±17 years; 33 female), 9 additional affected family members were detected from 2 families, with a single Brugada syndrome patient and 8 CPVT patients.
Conclusions--Provocative testing with adrenaline and procainamide infusions is useful in unmasking the etiology of apparent unexplained cardiac arrest. This approach helps to diagnose primary electrical disease, such as CPVT and Brugada syndrome, and provides the opportunity for therapeutic intervention in identified, asymptomatic family members who harbor the same disease.

 

Evaluation of left bundle branch block as a reversible cause of non-ischaemic dilated cardiomyopathy with severe heart failure. A new concept of left ventricular dyssynchrony-induced cardiomyopathy

Objectives We sought to determine if amelioration of left bundle branch block (LBBB)-induced contraction disturbances achieved by left ventricular (LV)-based pacing could result in sustained reversal of severe LV dysfunction in certain patients with chronic heart failure due to non-ischaemic cardiomyopathy.
Background It has been shown that LBBB induces asynchronous contraction of LV. However, whether such a functional contraction disturbance, if present for an extended period of time, could account for a dilated cardiomyopathy remains unknown.
Methods The study population comprised 29 patients with dilated cardiomyopathy, sinus rhythm, LBBB and severe heart failure (14 patients in New York Heart Association (NYHA) class III and 15 in class IV). Patients were followed prospectively after resynchronization therapy. LV function was considered to be normalized when ejection fraction (EF) was >50% at 1 year.
Results Five among the 29 patients (17%: group 1) demonstrated both complete normalization of LV function following resynchronization therapy (EF: from 19±6 to 55±3%, P=0.001) and clinical improvement (mean NYHA class: 3.4±0.5 to 1.8±0.4, P=0.02; 6-min walk distance: 300±136 to 444±75m, P=0.12; peak VO2: 11.9±4 to 15.8±2ml/min/kg, p=0.03). Among the remaining 24 patients (83%: group 2) EF improved but did not normalize (from 21±8 to 23±11%, ns). Baseline clinical features could not predict which patients would exhibit the reversal of LV dysfunction.
Conclusions
Normalization of LV function 1 year after resynchronization therapy in a small but important number of patients suggests that long-standing LBBB may be a newly identified reversible cause of cardiomyopathy.
 

Headaches and the Treatment of Blood Pressure Results From a Meta-Analysis of 94 Randomized Placebo-Controlled Trials With 24 000 Participants

Background— Uncertainty exists over whether blood pressure–lowering drugs prevent headache.
Methods and Results— A meta-analysis was carried out of the 94 randomized placebo-controlled trials of 4 different classes of blood pressure–lowering drugs (thiazides, ß-blockers, ACE inhibitors, and angiotensin II receptor antagonists) in fixed doses in which data on headache were reported. There were 17 641 participants who were allocated blood pressure–lowering drugs and 6603 who were allocated placebo. Treatment lowered systolic and diastolic blood pressures by 9.4 and 5.5 mm Hg, respectively, on average. One third fewer people on average reported headache in the treated groups (8.0%) than the placebo groups (12.4%) (odds ratio, 0.67; 95% CI, 0.61 to 0.74; P<0.001). About 1 in 30 treated persons benefited by having headache prevented. The prevalence of headache was reduced (P<0.001) in trials of each of the 4 classes of drugs.
Conclusions— Our results show that blood pressure–lowering drugs prevent a significant proportion of headaches. That this effect is seen with pharmacologically unrelated classes of drugs indicates that it is likely to be due to the reduction in blood pressure per se, the only recognized action that the drugs have in common. This in turn indicates that high blood pressure is a cause of headache, but this conclusion is not supported by observational studies of blood pressure and headache. The uncertainty over whether high blood pressure causes headache does not, however, detract from the practical benefits of the use of blood pressure–lowering drugs in preventing headaches and cardiovascular disease.
 

Significance of Tilt Table Testing in Patients with Suspected Arrhythmic Syncope and Negative Electrophysiologic Study

Background: The diagnostic significance of a tilt table test (TTT) in patients with a suspected arrhythmic etiology for syncope and negative electrophysiologic study (EPS) has not been previously assessed comparing the TTT results with the findings of prolonged monitoring using an implantable loop recorder (ILR). We sought to assess the diagnostic yielding of TTT in patients with suspected arrhythmic syncope and negative EPS.
Methods and Results: In 81 patients with suspected arrhythmic etiology for syncope and negative EPS, TTT was performed and an ILR implanted regardless the results of TTT. TTT was positive in 38 patients. During follow-up, syncope or presyncope recurred in 32 patients (39.5%). No differences were found in recurrence rates in patients with positive and negative TTT (31.5% vs 46.5%, P = ns). According to rhythm registered during ILR activation, mechanisms of syncopal events were classified as: arrhythmic (atrioventricular [AV] block and ventricular tachycardia; n = 18), neurally mediated (sinus bradycardia and sinus pause; n = 9), and indeterminate (normal sinus rhythm; n = 5). There was no statistical association between the results of TTT and the mechanism of syncope.
Conclusions: In patients with a suspected arrhythmic etiology for syncope and a negative EPS, TTT is of little value to predict the mechanism of syncope and the ILR implantation seems to be a useful and safe diagnostic strategy.
 

Blood glucose: A strong risk factor for mortality in nondiabetic patients with cardiovascular disease

Background The prognostic significance of blood glucose (BG) for nondiabetic patients in a stable chronic phase of cardiovascular disease (CVD) has been sparsely investigated, especially for glucose within the normal range. In particular, it is unknown if for these patients there is a graded relation of mortality to glucose or if there is a lower threshold.
Methods We used the Framingham Heart Study 30-year data to determine 2-year all-cause, cardiovascular mortality (CVM), and non-CVM risk adjusted for age, sex, and typical cardiovascular risk factors (systolic blood pressure, total cholesterol, body mass index, cigarette smoking, and use of antihypertensive drugs) by levels of random whole BG for non–glucose-intolerant subjects (glucose intolerance includes diabetes mellitus) with existing CVD.
Results There were steep graded relations of 2-year all-cause, CVM, and non-CVM to BG throughout the normal and subdiabetic range with no evidence of a lower threshold. Two-year mortality continuously increased from 2.99% at the bottom of the normal range (BG = 60 [plasma equivalent = 67] mg/dL) to 7.23% at the top of the normal range (89 [plasma equivalent = 100] mg/dL) (a 2.42-fold increase) and then continued to further continuously increase, reaching 11.38% at 119 [plasma equivalent = 133] mg/dL, the top of the glucose range considered (P for trend <.0001). There were analogous steep increases for CVM and non-CVM.
Conclusions Blood glucose, even within the normal range, is a strong independent predictor of 2-year all-cause, CVM, and non-CVM in nondiabetic subjects with CVD and therefore of prognostic significance for these high-risk patients.
 

Efficacy and Safety of Cryoenergy in the Ablation of Atrioventricular Reentrant Tachycardia Substrates in Children and Adolescents

Introduction: Cryoenergy has evolved as a safe and effective alternative for ablation of arrhythmia substrates in adult patients. Due to two specific features, cryomapping and cryoadhesion, this technique appears very attractive for pediatric patients minimizing complications and fluoroscopy time. The aim of the study was to investigate efficacy and safety of cryoenergy in the ablation of supraventricular tachycardia (SVT) substrates in pediatric patients.
Patients and Methods: Thirty-two patients (mean age: 10.1 ± 3.5 years) with SVT (accessory pathways: n = 19; atrioventricular nodal reentrant tachycardia (AVNRT): n = 13) underwent electrophysiological study under the guidance of the LocaLisa® system. Cryomapping at 30°C was performed to predict cryoablation outcome and to ascertain AV conduction. Cryoenergy was delivered subsequently at the same spot (cryoablation at 70°C) as verified by the LocaLisa® system.
Results: Successful cryoablation was achieved in 24 of 32 patients (75%). A median of two (1 10) cryoablations were delivered. In the remaining 8 patients, radiofrequency (RF) current application was effective in 5 resulting in an overall success rate of 90.6%. In 4 patients with an accessory pathway cryomapping was not predictive for successful cryoablation (negative predictive value 66.6%). In 3 additional patients with AVNRT transient high-grade AV block occurred during cryoablation despite previous "safe" cryomapping at the same location. No other major complications were noted.
Conclusion: Cryoablation of SVT substrates in pediatric patients was associated with a lower success rate compared to RF catheter ablation. Cryomapping decreased the number of permanent lesions but did not predict cryoablation outcome in all tachycardia substrates.
 

Reproducibility of nitrate-stimulated tilt testing in patients with suspected vasovagal syncope and a healthy control group

Objective Nitrate-stimulated tilt testing may be used to diagnose vasovagal syncope or to guide therapy. To date, the reproducibility of the test in patients with clinically suspected vasovagal syncope and healthy controls is undetermined. A high reproducibility is a prerequisite for correct interpretation of the test result. This study investigates the reproducibility of a nitrate-stimulated tilt test in patients with clinically suspected vasovagal syncope and a healthy control group.
Methods and Results We studied 43 patients (24 women, 19 men) with a typical history of vasovagal syncope and 18 healthy controls (3 women, 15 men). We used a combined tilt protocol with a 30-minute passive and 15-minute nitrate-stimulated phase. The second tilt test was performed 16 ± 12 days after the first. In both patients and controls, overall positive tilt responses were reproduced in the second test in 100%. In contrast to this, the reproducibility of an overall negative test was 50% in patients but 93% in controls. Overall hemodynamic responses to tilt were reproducible in 80%.
Conclusion Nitrate-stimulated tilt testing in both patients with suspected vasovagal syncope and controls has an excellent reproducibility of positive results but a moderate reproducibility of negative results. Importantly, these results are still valid at a repeat interval of 2 weeks and longer. These data suggest that in patients with suspected vasovagal syncope, a nitrate-stimulated tilt test may provide a suitable tool to evaluate the efficacy of a therapeutic approach.
 

Atrial Response to Ventricular Antitachycardia Pacing Discriminates Mechanism of 1:1 Atrioventricular Tachycardia

Background: Inappropriate shocks from implantable cardioverter defibrillators (ICD) remain a significant clinical problem despite device discrimination algorithms. The atrial response to antitachycardia pacing (ATP) may determine the mechanism of 1:1 A:V tachycardia.
Methods: For this study we refer to sinus tachycardia, atrial tachycardia (AT), atrial fibrillation, and flutter as atrial tachycardia (AT), and all other tachycardia as "non-AT." Three atrial response patterns during the burst of ATP were determined. The atrial cycle length (ACL) may be unchanged (type 1) indicating AT. The ACL may show variation during ATP (type 2) indicating variable VA block and does not discriminate between an AT and a non-AT mechanism, in which case a default diagnosis of non-AT is made. The ACL may accelerate to the ATP cycle length (type 3) indicating entrainment. A VAAV response at the end of ATP was considered diagnostic of AT (type 3A) whereas a VAV or VVA response was considered a non-AT mechanism (type 3B). This algorithm was applied to ICD tracings from 68 episodes of spontaneous 1:1 A:V tachycardia that had 136 sequences of ATP administered. The rhythm "truth" was determined by consensus of two experienced clinicians.
Results: The algorithm correctly identified AT with a sensitivity of 71.9% (95% CI: 67.1 73.6), and specificity of 95% (83.5 99.1). The PPV was 97.2% (90.9 99.5), and NPV 58.5% (51.4 61.0). Kappa was 0.57 (0.43 0.62). If used clinically the algorithm would have aborted 53.3% (8/15) of inappropriate shocks delivered into an AT-mechanism tachycardia and would not have withheld a shock for any episode of VT.
Conclusion: Analysis of atrial response patterns during and after ventricular ATP can successfully discriminate tachycardia mechanism and may reduce inappropriate ICD shocks.
 

Randomized comparison of anterolateral versus anteroposterior electrode position for biphasic external cardioversion of atrial fibrillation

Background In biphasic external cardioversion (CV) of atrial fibrillation (AF), the influence of different electrode positions on efficacy and incidence of early recurrent atrial fibrillation is not known. This study compared anteroposterior (AP) vs anterolateral (AL) electrode positioning.
Methods Consecutive patients referred for CV of persistent AF were randomized either to an AP or an AL electrode position. Biphasic external CV was performed with standardized electrode positions and rising energy delivery.
Results Both groups (N = 123, mean age 66 years, 71% male, 83% with structural cardiovascular disease or hypertension) did not differ concerning age, sex, body mass index, chronic antiarrhythmic therapy, duration of AF, left ventricular ejection fraction, and left atrial diameter. Cumulative success rates were comparable (AP 94.9% vs AL 95.2%, P = ns). First-shock efficacy did not differ (AP 78.3% vs AL 74.6%, P = ns). Early recurrent atrial fibrillation (AF relapse <1 minute after successful CV) occurred in 8.1% (AP 11.6% vs AL 4.8%, P = ns). Mean number of shocks was 1.3 per patient with the AP configuration and 1.4 per patient with the AL configuration (P = ns). Mean cumulative energy delivery was also comparable (AP 171 WS vs AL 198 WS, P = ns).
Conclusions Both electrode positions are similar in biphasic external CV of AF with regard to acute success and early recurrent atrial fibrillation. Also, the number of shocks needed and energy delivery are comparable with both electrode configurations.
 

Efficacy and Safety of Radiofrequency Catheter Ablation of Atrioventricular Nodal Reentrant Tachycardia in the Elderly

Introduction: Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common regular supraventricular tachycardia in the general population as well as in elderly patients. The purpose of the study was to investigate the success and complication rate particularly regarding the induction of an atrioventricular (AV) block by radiofrequency (RF) ablation in elderly patients with and without a preexisting AV block.
Methods and Results: Between February 1998 and July 2004, all patients with symptomatic AVNRT referred for slow-pathway ablation in our institution were included and divided into two groups: group 1 patients younger than 75 years (n = 508) and group 2 patients 75 years (n = 70).
A preexisting prolonged PR interval was present in 17 (3.3%) patients of group 1 and in 26 (37%, P < 0.0001) patients of group 2. Following successful slow-pathway ablation (follow-up time group 1: 37 ± 22, group 2: 37 ± 24 months) no induction of an AV block was observed in group 2 but in four patients of group 1 (0.79%) a complete heart block was induced requiring a pacemaker implantation. In group 1, 15 (2.95%) patients with a recurrence of AVNRT were readmitted for a repeat ablation procedure. No recurrences occurred in group 2.
Conclusion: Despite a higher incidence of preexisting prolonged PR intervals slow-pathway ablation in elderly patients is both effective and safe and should be considered as the first line therapy also in this patient population
 

Catheter Ablation of Atrial Fibrillation Versus Atrioventricular Junction Ablation Plus Pacing Therapy for Elderly Patients with Medically Refractory Paroxysmal Atrial Fibrillation

Background: Catheter ablation of atrial fibrillation (AF) has become another nonpharmacologic therapeutic option for medically refractory paroxysmal AF. Whether this method is better than atrioventricular (AV) junction ablation plus pacing therapy is unknown. The purpose of this study was to compare the very long-term (longer than 4 years) clinical outcomes of the 2 methods in elderly patients (>65 years old) with medically refractory paroxysmal AF.
Methods: From January 1995 to December 2001, 71 elderly patients with medically refractory paroxysmal AF were included; group 1 included 32 patients with successful AV junction ablation plus pacing therapy and group 2, 37 patients with successful catheter ablation of AF.
Results: After a mean follow-up of more than 52 months, the AF was better controlled in the group 1 patients than group 2 (100% vs 81%, P = 0.013), however, they had a significantly higher incidence of persistent AF (69% vs 8%, P < 0.001) and heart failure (53% vs 24%, P = 0.001). Furthermore, the incidence of ischemic stroke and cardiac death was similar between the 2 groups. Compared with the preablation values, a significant increase in the NYHA functional class (1.7 ± 0.9 vs 1.4 ± 0.7, P = 0.01) and significant decrease in the left ventricular ejection fraction (44 ± 8% vs 51 ± 10%, P = 0.01) were noted in the group 1 patients, but not in the group 2 patients.
Conclusions: Although AV junction ablation plus pacing therapy better controlled the AF in elderly patients with medically refractory paroxysmal AF, that method was associated with a higher incidence of persistent AF and heart failure than catheter ablation of AF in the very long-term follow-up.
 

Long-Term Incidence of Malignant Ventricular Arrhythmia and Shock Therapy in Patients with Primary Defibrillator Implantation Does Not Differ from Event Rates in Patients Treated for Survived Cardiac Arrest

Introduction: Recent trials have demonstrated benefit of prophylactic defibrillator (ICD) implantation compared to conventional treatment in high-risk patients. However, many patients have rare or no sustained arrhythmias following implantation. Our study addresses the question, whether patients with prophylactic defibrillator implantation have a lower risk for life-threatening ventricular tachycardia (VT) or ventricular fibrillation (VF) compared to sudden cardiac death (SCD) survivors.
Methods and Results: Over 7 years we enrolled 245 patients. Occurrence of spontaneous sustained VT/VF resulting in adequate ICD treatment was the endpoint. Incidence, type, and treatment of sustained arrhythmia in 43 previously asymptomatic ICD recipients (group B) were compared to data of 202 survivors of imminent SCD (group A). All patients had severely impaired left ventricular ejection fraction (<45%). Group B patients had long runs (>6 cycles, <30 s) of VT during Holter monitoring and inducible sustained arrhythmia. Incidence of rapid VT and VF (cycle length <240 ms/heart rate >250 bpm) after 4 years (35% in both groups, P = ns) and adequate defibrillator therapies (57% vs 55%, P = ns) were similar in both groups after univariate and multivariate analysis. Cumulative mortality tended to be lower in group B compared to group A, but the difference was not statistically significant.
Conclusion: During long-term follow-up, incidence