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A 72 year-old woman complained of attacks of palpitations and syncope. Complete heart block was diagnosed at another center and a temporary pacemaker was inserted . She was referred for implantation of a permanent pacemaker.

Examination of the 12 lead ECG during pacing shows a RBBB pattern with positive V1 and superior axis suggestive of pacing from LV apex. Fluoroscopy confirmed that temporary lead was inadvertently inserted through a patent foramen ovale into LV apex. EP study was performed. The following tachycardia was easily inducible . Asystole followed the termination of the tachycardia. What is the mechanism of the tachycardia and what would you do next?

This is a typical counterclockwise atrial flutter confirmed by entrainment studies from the right isthmus. RF ablation was targeted at posterior isthmus and bidirectional block was induced.

Flutter was not inducible anymore, no AV block was present but asystole persisted, hence a diagnosis of sick sinus syndrome (bradycardia-tachycardia syndrome). As the temporary lead was inserted into LV, a trans-esophageal echocardiogram was performed and it showed a long string of clot attached to the lead inside LA. Heparin was started and she was transferred back to the referring center pending a decision of either thrombolytic therapy or surgical removal of the clot. It took a whole week in that center to reach to a decision and when a repeat TEE was performed no clot was evident anymore! Patient was well and there was no evidence of any emboli. A dual chamber pacemaker was implanted and she has been asymptomatic during the last 6 months after the procedure.

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Holter recording from a 5-month old baby with attacks of cyanosis.

Another part of the recording is shown. What treatment do you recommend?

First ECG shows complete AV block and prolonged QT intervals. The second one shows early-coupled PVCs inducing a run of polymorphic VT(Torsade de pointes). Other parts of the holter showed long runs of sustained polymorphic ending with long periods of systole . The long QT and ventricular arrhythmias was considered secondary to the heart block.

A single chamber pacemaker was implanted and he has been doing well and free of symptoms during the last few months.


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Surface ECG and 12-lead ECG of the tachycardia in a young man with recurrent wide QRS tachycardia.

During EP study atrial pacing was performed . Two tachycardia morphologies were induced by RV pacing studies . What's your diagnosis now?

There is minimal preexcitation during sinus rhythm but atrial pacing shows increasing preexcitation. The first tachycardia has a morphology similar to the maximal preexcitation noted during atrial pacing and the earliest atrial activation is recorded at proximal CS, hence AV node. The second tachycardia has right bundle branch block morphology but not similar to the delta waves during atrial pacing. The earliest atrial activation of this tachycardia is recorded at distal coronary sinus.

So, the first tachycardia is an antidromic tachycardia using a left sided accessory pathway as the antegrade limb and AV node as the retrograde limb. The second one is an orthodromic tachycardia with RBBB aberrancy.

A single application of RF energy at distal CS resulted in disappearance of delta (RF artifact obscures the surface ECG but separation of A and V signals are evident on RF channel). No delta was present thereafter and no tachycardia was inducible.


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Holter recording from a 23 year old man.

This is also just an artifact.

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Holter recording from a 23 year old man.

This is also just an artifact.

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Holter recording from a 56 year old man with palpitations.

This is nothing but artifact, misinterpreted as VT!

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Young woman with recurrent syncope. This is a Holter recording.

Tracings show a bidirectional ventricular tachycardia. This is another case of Catecholaminergic polymorphic VT.

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A hypertensive patient presenting with dyspnea.

ECG shows atrial tachycardia with 2:1 ventricular conduction. Every other P waves falls on the summit of the T wave resembling a bifid T wave. This is best evident at inferior leads. RF ablation was suggested.

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Young woman with attacks of palpitations.

ECG shows a wide QRS tachycardia with LBBB morphology and inferior axis. Dissociated P waves are easily seen at lead II. This is suggestive of a Ventricular tachycardia arising from right ventricular outflow tract. The heart was structurally normal hence idiopathic ventricular outflow tract tachycardia. The arrhythmia is amenable to curative RF ablation. This patient preferred drug therapy for now.

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An attack of rapid palpitations followed by cardiac arrest .

This is a typical example of preexcited atrial fibrillation (WPW and AF). This high risk arrhythmia can easily degenerate into VF.


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This 6 years-old asymptomatic girl was referred for further evaluation of risk. Her sister had died suddenly at the age of 9, though she had experienced two episodes of apparently unexplained syncope in the preceding few months. Her aunt had also died suddenly at a young age. What would be the next step?

An echocardiogram and 24-hour Holter recording were normal. Procainamide challenge test was negative. ECG stress test was normal except for a few PVCs at the maximal stress. What would you do next?

Isoproterenol infusion was tried and the following arrhythmia was induced and stopped after stopping the infusion . What's the diagnosis?

Catecholaminergic polymorphic ventricular tachycardia.


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Young man with syncope.

ECG is suggestive of Brugada Syndrome. VF was easily inducible during electrophysiologic study . An ICD was implanted.


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Two ECGs from a middle-aged man referred because of palpitations.

The first ECG shows a slow ventricular tachycardia originating from right ventricular outflow tract (Idiopathic RVOT VT) with retrograde P waves. RF ablation was advised but he preferred medical therapy.


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Holter recording of a young woman with palpitations.

Artifacts! You can even see the true QRS complexes within artifacts.


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65-year-old woman with dizziness.

Intracardiac electrograms are demonstrated. It shows sinus rhythm with a typical 2:1 infranodal AV block. A His signal is evident after an every other A wave without being conducted to the ventricles. On surface ECG the blocked P waves are superimposed on T waves.


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Recording during Holter monitoring of a 25 year-old young man with recurrent syncope despite treatment with multiple anti-epileptic and anti-arrhythmic drugs including amiodarone.

Previous investigations including resting ECG, echocardiogram as well as neurologic evaluations had been negative.

What's your diagnosis and what would you do next?

Stress test was performed and showed the following findings

What's your diagnosis now?

This is a typical case of Catecholaminergic Polymorphic VT. An ICD was implanted and a high dose beta-blockers was started. He has remained asymptomatic during the last year since diagnosis.


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17 year old young man with recurrent palpitations refractory to multiple anti-arrhythmic drugs.

Tachycardia was induced during EP study. Intracardiac recordings are shown . VA interval was measured as 64ms.

What is your diagnosis?

Later on some changes were noted . What now?

12-lead ECG showed a wide QRS tachycardia with right bundle branch block pattern and left axis deviation. First intracardiac recording shows 1:1 VA conduction, so a supraventricular tachycardia with aberrancy cannot be ruled out. However, during the second recording intermittent VA conduction is evident. This finding as well as the QRS morphology are suggestive of left fascicular ventricular tachycardia. It was ablated at left mid-septal area.


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A 29 year-old man with frequent wide QRS tachycardia.

Intracardiac recordings are shown . A narrow QRS tachycardia was also inducible .

What do you think?

Tachycardia was inducible by RA premature stimulations. It could be easily entrained by RV pacing during the tachycardia but decremental RV pacing showed VA block .

What do you think now?

Despite lacking VA conduction at longer cycle lengths, it was demonstrable with RV pacing at more rapid rates.

Mapping during the tachycardia showed the earliest atrial activation at left posteroseptal area and the accessory pathway was ablated at this area .


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Young man with frequent wide QRS tachycardia changing to a narrow one.

Intracardiac recordings showed a concentric pattern of VA conduction with no change in tachycardia cycle length nor VA interval during LBBB aberrancy. Parahisian pacing is shown.

During mapping with the RF catheter, delta disappeared with the pressure of the catheter. What is the diagnosis?

The findings are typical of a para-hisian accessory pathway. A large His signal is recorded by RF catheter after disappearance of delta. These accessory pathways are sometimes very superficial and as seen in this case may disappear with catheter pressure. Delta recurred later on but he has had a few short attacks of tachycardia afterwards, off drugs (possibly a damaged pathway). He is not willing to accept the risk of burn at this area.


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A 49 year-old woman with incessant tachycardia.

This patient had an incessant atrial tachycardia originating close to His area. There is a risk of AV block with ablation at this site and she decided not to proceed to RFA at this time. Antiarrhythmic drugs were started.


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8 year-old boy with attacks of loss of consciousness despite treatment with anti-epileptic drugs. One of his siblings had died at age 6.

ECG shows Long QT syndrome, an unfortunately commonly misdiagnosed condition. Some ECGs showed even more marked T wave and QT changes.


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Young man with palpitations. ECG after the attack is shown. The irregular wide QRS tachycardia is suggestive of WPW syndrome and after the attack was terminated by DC shock, ECG confirms the diagnosis. It was ablated at left posterior area.


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A 46 year-old woman with frequent palpitations during the last 25 years.

Retrograde P waves were evident during the tachycardia. She was studied. Intracardiac recordings showed earliest atrial activation at High Right Atrial electrodes. Further mapping showed the presence of a concealed right anterior accessory pathway that was successfully ablated.


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This 64 year old man had a history of frequent attacks of palpitations that lasted for several hours and then terminated spontaneously. He had been refractory to multiple anti-arrhythmic drugs. An attack started in our office when he was waiting to be visited. The following ECG was recorded.

The first ECG shows atrial fibrillation with a rapid ventricular response. He was diagnosed as lone atrial fibrillation. The second one shows atrial flutter. In some patients atrial flutter is a trigger for atrial fibrillation and isthmus ablation may eliminate or reduce the attacks of AF. RF ablation of posterior isthmus was performed for this patient and he has only had a short episode of palpitation during the last 4 months of follow-up.


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Rhythm strip recorded from a 60 year-old woman with recurrent syncope. Baseline ECG follows . Echocardiogram and lab tests were normal.

ECG shows complete heart block with a markedly prolonged QT interval and the strip shows PVCs culminating in a rapid polymorphic ventricular tachycardia, hence tosade de pointes. No other predisposing factor was found. A dual chamber pacemaker was implanted and there has never been any symptoms during the last year.

Courtesy of Dr. Mansoor Esmaili.


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A woman in 50s with palpitations and a history of coronary bypass surgery. She was receiving digoxin, metoprolol and amiodarone.

Answer: Intracardiac recordings confirmed the diagnosis of typical counterclockwise atrial flutter. It stopped with linear ablation of posterior isthmus . Sinus bradycardia was present post-RFA but normal sinus rhythm resumed gradually . Digoxin and amiodarone were discontinued.


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A 20 year old woman with frequent attacks of SVT was studied. The surface ECG recordings during decremental atrial pacing are shown. What is the diagnosis?

Intracardiac recordings are shown. What do you think now?

Answer: The intra-cardiac recording shows increasing pre-excitation with atrial pacing. However, unlike the usual accessory pathways, the interval between the pacing spike and delta wave increases with decreasing pacing cycle length, i.e. antegradely decremental accessory pathway or Mahaim pathway. It was ablated at right posterolateral area . Interestingly, this case had an associated AV nodal reentrant tachycardia which was also ablated.

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Tracing obtained during exercise test of a 46 year-old man with atypical chest pain and palpitations.

Answer: The electrocardiographic pattern of AV dissociation and LBBB and inferior axis morphology are suggestive of right ventricular outflow tract tachycardia. No ST segment changes were detected during the test and an echocardiogram was normal. A diagnosis of Idiopathic RV outflow tract tachycardia was made. Intracardiac recording during EP study confirmed the presence and origin of RVOT VT and it was successfully ablated at septal side of RVOT just below Pulmonic valve.


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This patient presented with frequent palpitations during the last several months. RF ablation was tried at another center with no success. Holter recording is shown.

Intracardiac recordings during RV pacing are shown. What is diagnosis?

Answer: VA conduction changes from a concentric pattern (AV nodal) to an eccentric one with earliest atrial activation at distal coronary sinus. The concealed accessory pathway was ablated at left lateral area. It is unusual for this type of accessory pathway to present with such a repetitive pattern as shown on Holter monitoring.

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52 year-old woman with recurrent wide QRS tachycardia. It was induced during EP study and changed in morphology by ventricular pacing.

Intracardiac recordings are shown. What is diagnosis?

Answer: Concentric pattern of VA conduction and the very short VA interval point to the diagnosis of AV nodal reentrant tachycardia. The diagnosis was confirmed by other EP criteria. Both RBBB and LBBB aberrancy were observed in this case.


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This 18 year-old young man had frequent palpitations and dizziness for whom a single chamber pacemaker had been previously implanted. Palpitations persisted and were unresponsive to multiple anti-arrhythmic drugs. 

Answer: EP Study showed an almost incessant atrial tachycardia . When it stopped for a few moments, a pause and pacemaker capture followed. It looked like a bradycardia-tachycardia syndrome. Mapping showed the earliest atrial activation at right posteroseptal area . With the first application of RF energy tachycardia stopped and a stable sinus rhythm followed . Interestingly there were no signs of sinus node dysfunction and sinus node recovery indices were normal. Pacemaker was programmed to VVI 40.

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A 58 year-old woman with previous implantation of a VVIR pacemaker was referred because of two prolonged episodes of loss of consciousness. Holter recording is shown. No structural heart disease was documented.

Answer: Prolonged QT interval is obvious. Even more bizarre QT prolongation was documented during one of the episodes. No cause was found for the prolonged QT interval. She could recall the onset of first symptoms back to a few years ago, quite unusual for the congenital LQTS. ECG recording from the time of pacemaker implant were not available. Upgrade of her pacemaker to an ICD was recommended but it was refused by the patient. Pacemaker was programmed to a higher lower heart rate and a beta blocker was started. We had a report from her referring cardiologist that she passed away a few months afterwards.

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Young man with frequent palpitations. No findings at echocardiography and stress test.

During EP study, tachycardia with the same morphology was induced. Intracardiac recordings are shown . When more rapid it showed the following pattern . What could it be?

Answer: First tracing showed 1:1 VA conduction but HV is slightly negative and later the VA conduction changed to 2:1. Findings were suggestive of a ventricular tachycardia. The relatively narrow QRS could be explained by close proximity and penetration into AV conduction system. It was mapped to an area close to His, so it was decided to proceed to RF ablation at the moment. Any comments?

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A young with abrupt syncope. He was cardioverted with DC shock.

Answer: This rapid irregular wide QRS tachycardia was due to AF with preexcitation over a left posteroseptal accessory pathway.

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A middle aged woman with several attacks of palpitations, many of which had occurred during exertion. Attacks usually responded to verapamil injections.

Intracardiac recordings are shown.   What is the diagnosis?

Answer: Intracardiac tracing shows ventricular tachycardia with VA wenckebach. The morphology and characteristics of the tachycardia are compatible with the diagnosis of fascicular VT. Nice diastolic and purkinje potentials were found at left mid ventricular septal area and after the first application of RF energy the tachycardia was no longer inducible.

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An interesting ECG finding during EP study of a patient presenting with unidentified syncope.

Intracardiac recordings were more interesting. What's your diagnosis?


Answer: This looks to be a rare phenomenon of infrahisian wenckebach. You can see that HV prolongs in the second beat and blocks in the third and this repeats again and again. Interestingly, AV conduction is aberrant with the first beat which has the shortest HV interval.

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47 year-old woman with frequent attacks of palpitations, even on amiodarone.

Retrograde P waves are evident well outside QRS complexes during the tachycardia. EP study showed the presence of dual AV nodal physiology (AH jump) and a long VA tachycardia was inducible by RV extrastimuli . As intracardiac recordings show this is a case of atypical AVNRT (fast-slow type). It was no longer inducible after slow pathway modification. 

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Young woman with a long history of frequent palpitations.

Answer: P waves looking similar to sinus ones are seen to appears in runs. Atrial tachycardia was documented at electrophysiologic study . During the subsequent mapping it was found to originate from lower SVC and was successfully ablated.

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This 25 year-old man had survived a sudden cardiac arrest. No structural heart disease was found.

ECG findings of both Brugada syndrome and long QT syndrome are present. Typical findings of both syndromes were also present in other family members. The ECG of one of his asymptomatic brothers follows . This is a very rarely reported finding.

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A 23 year-old young man was referred with a long history of frequent palpitations, even occurring several times daily. A sample of Holter recording is shown.

Surface ECG during tachycardia was obtained. Intracardiac tracing during tachycardia follows.

What is your diagnosis now?

Retrograde P waves are evident during the tachycardia, though RP interval is less than PR. This is in favor of the presence of an accessory pathway. Intracardiac tracing shows an AV reentrant tachycardia with earliest retrograde atrial activation recorded by HRA and His electrodes. The concealed accessory pathway was ablated at right anterior area. The pathway was relatively slowly conducting retrogradely with VA interval at the site of ablation about 160ms. This may have been responsible for the clinical presentation which resembled that of PJRT.

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ICD interrogation from a 52 year-old man with dilated cardiomyopathy and recurrent syncope. ICD had been implanted 4 years ago and previously he had only had inappropriate discharges due to AF with rapid ventricular responses. Inappropriate discharges had been controlled by AV junctional ablation one year ago.

The interrogation shows regular ventricular pacing (VP) at the upper part. A few PVCs (VS) appear and ventricular fibrillation (FS) follows. It was defibrillated successfully by a 30j shock.

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A 37 year-old woman with attacks of palpitations. Another narrow supraventricular tachycardia with retrograde P waves well outside QRS complexes. This case proved to be atypical AVNRT in mechanism and was cured by slow pathway ablation. Ventriculo-atrial time was 95ms, as shown in the intracardiac tracing.

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A 65 year old woman with frequent palpitations.

Retrograde P waves are evident after QRS in many lead. P waves so separate from QRS complex are usually suggestive of the presence of a concealed accessory pathway or atypical AV nodal reentrant tachycardia (AVNRT) but it proved to be a typical AVNRT at EP study.

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What is the likely tachycardia mechanism?

If you look at the cycle length of the tachycardia it is evident that the cycle length is longer (faster tachycardia) when left bundle branch aberrancy is present. This is typical of the presence of a concealed left free wall accessory pathway .

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45 year old woman with uncontrollable frequent palpitations.

At EP study frequent induction of tachycardia made formal studies impossible. In addition to the above tachycardia another one was easily inducible .

Answer: The two tracings are similar in QRS morphology but negative P waves are evident after QRS complexes of the first one,  specially at lead III but no P waves are seen in the second tracing. This raises the suspicions of two tachycardia mechanisms. EP study was difficult because of easy induction of tachycardia with minimal extrastimuli. Two concealed accessory pathways were identified: a left lateral accessory pathway (first ECG) and a parahisian accessory pathway (second ECG). Left one was ablated but the ablation of the parahisian accessory pathway was deferred to another session after discussion of the risk of AV block with the patient and her relatives.

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50 year-old man with episodes of palpitation and dizziness.

ECG shows RBBB pattern and intermittent preexcitation. AV reciprocating tachycardia was easily inducible at EP study. The accessory pathway was ablated at right posterior area.

Post-RF ECG showed RBBB but no preexcitation.

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A 64 year old man with chest pain admitted in emergency room.

ECG shows preexcitation suggestive of a right posteroseptal accessory pathway. Deep Q waves at inferior leads may mimic myocardial infarction.

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Young man with palpitations.

This is wenckebach phenomenon and may be observed normally, specially in young people.

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This 66 yr old man presented with a hypotensive tachycardia needing DC shocks for termination. Attacks had recurred despite oral amiodarone. No organic heart disease was found.

Tachycardia morphology is suggestive of VT. At EP study a sustained VT morphologically different from the above clinical tachycardia  was also inducible. This one originated from LV apical area but was hemodynamically unstable and could not be mapped. Despite absence of structural heart disease, an early stage cardiomyopathy cannot be ruled out and the prognosis may be guarded.

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A 75 year old woman with an incessant tachycardia during the last few months.

Holter recording is shown here. What has happened and does it help in diagnosis?

ECG shows a slow narrow supraventricular tachycardia with obvious P waves, negative in inferior waves. The most common diagnosis with this presentation at this age is atrial tachycardia. The Holter recording, however, shows an interesting phenomenon. Tachycardia terminates by runs of PVCs. This is rare with atrial tachycardias and is more compatible with the presence of accessory pathways or more common at this age and sex AV nodal reentrant tachycardia.

At EP study the mechanism was found to be AVNRT and slow pathway ablation terminated the tachycardia.

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An old man with VVIR pacemaker.

Answer: Pacemaker is functioning normally but note the paced QRS configuration. It has a pattern of RBBB with superior axis indicating pacing from low LV. Pacemaker lead had passed through a PFO into LV.


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