Retrograde Migration of the Site of Functional Block:

Retrograde Migration of Functional Block. Introduction : Functional bundle branch blocks during supraventricular tachycardia have been described, and their sustainment has been attributed to concealed conduction. Such blocks frequently resolve spontaneously, but the electrophysiologic mechanism of resolution bas not been well described. This report describes the resolution of functional bundle branch block through proximal migration of the site of block.
Methods and Results : During electrophysiologic study of a patient with reentrant antidromic tachycardia via an atriofascicular accessory pathway, functional retrograde right bundle branch block could be readily induced following tachycardia initiation with right ventricular apical pacing. Resolution of this block was associated with shortening of the tachycardia cycle length. Electrogram recordings along the right bundle branch during tachycardia determined that resolution of the functional retrograde right bundle branch block was associated with migration of the site of block from the distal to the proximal right bundle. When the site of block was directly at the recording site, both anterograde and retrograde activation of the right bundle was demonstrated.
Conclusion : Migration of the site of block is a mechanism of resolution for functional conduction blocks maintained by concealed conduction.     

Reentry tachycardia with complete atrioventricular dissociation probably connected with the right Maha?m bundle]

A case of reentrant tachycardia with narrow and wide ventricular complexes without appearances of preexcitation is reported. Electrophysiological investigation showed complete retrograde atrioventricular block during tachycardia; left bundle branch block did not show the tachycardia rate. The reentry loop probably comprised: the His bundle, the right bundle branch, a right Maha?m bundle and possibly a myocardial bridge. Possible intra-hisian reentry is discussed. The initiation of the tachycardia is analysed together with the possible consequences of permanent cardiac pacing.     

Successful treatment of ventricular tachycardia by transvenous electrical ablation of the right Tawara branch

Recurrent episodes of ventricular tachycardia not responding to medical treatment occurred in a 56 year old man. Electrophysiological investigation showed ventricular tachycardia due to bundle branch reentry. Using a method similar to catheter ablation of the atrioventricular junction an ablation of the right bundle branch was performed by an electrical shock of 250 J. While before the ablation ventricular tachycardia occurred several times a day, and its induction by programmed ventricular stimulation was facilitated by the administration of antiarrhythmic drugs, no initiation of ventricular tachycardia was possible after ablation of the right bundle branch. Over a follow-up of 4 weeks the patient has not suffered from tachycardia and the artificial right bundle branch block persists.     

Bundle branch reentry ventricular tachycardia in arrhythmogenic right ventricular dysplasia

A 42-year-old male had history of recurrent palpitation and was documented to have wide QRS tachycardia. Magnetic resonance imaging angiogram showed evidence of arrhythmogenic right ventricular dysplasia and severe right ventricular dysfunction. Electrophysiology study showed evidence of bundle branch reentry ventricular tachycardia. It was successfully treated by radiofrequency ablation of right bundle branch. This is probably the first case of bundle branch reentry as a mechanism for ventricular tachycardia in a case of arrhythmogenic right ventricular dysplasia.     

Bundle branch reentrant tachycardia treated by electrical ablation of the right bundle branch

A 66 year old man presented with multiple episodes of tachycardia. Some had QRS complexes with a right bundle branch block configuration identical to those of sinus beats. The onset of the tachycardia was preceded by premature His bundle depolarizations. There was a His potential before each QRS complex of the tachycardia. Atrial activity was dissociated. Occasionally the appearance of sinus beats with a left bundle branch block pattern announced a tachycardia with an identical configuration and atrioventricular dissociation. His bundle activity occurred before the QRS complex and was followed by a right bundle branch deflection. A reentrant mechanism within the bundle branch system was invoked. One 200 J shock was delivered through an electrode catheter to the site of the right bundle branch. The postprocedure course was uneventful (follow-up 10 months).     

"Slowing" right bundle-branch block in reciprocating tachycardia from a latent right lateral Kent bundle

The authors report the case of a 56 year old man with paroxysmal reciprocating tachycardia. The participation of a right lateral Kent bundle, latent in sinus rhythm and with retrograde atrioventricular conduction during tachycardia was proved by : 1) the slowing of the tachycardia rhythm and lengthening of the ventriculo-atrial conduction time by 50 ms during right bundle branch block ; 2) atrial mapping during tachycardia showing right lateral atrial pre excitation ; 3) the spontaneous termination of some attacks after a blocked Hisian depolarisation. Analysis of the mechanisms of spontaneous termination of tachycardia showed a block in the accessory pathway in 80% of cases, leading to the successful use of Amiodarone. The particular electrophysiological mechanism of functional bundle branch block makes it the most reliable positive diagnostic criterion in reciprocating tachycardia. A review of previously reported series shows participation of right lateral and septal accessory pathways to be uncommon during reciprocating tachycardia. Functional bundle branch block does not necessarily lengthen the ventriculo-atrial interval with septal accessory pathways. Left lateral Kent bundles are much more common. These points are analysed together with the mechanism of functional bundle branch block in the discussion.     

Facilitation of Sustained Bundle Branch Reentry by Atrial Fibrillation

Sustained Bundle Branch Reentry. An electrophysiologic evaluation was performed in a patient with an idiopathic dilated cardiomyopathy and syncope. Ventricular tachycardia was not inducible despite the use of a variety of pacing maneuvers during sinus rhythm. Only after the electrical induction of atrial fibrillation did sustained bundle branch reentrant tachycardia (with both right and left bundle branch block QRS configurations) spontaneously occur and become reproducibly induced during right ventricular pacing. Ablation of the right bundle branch eliminated reproducibility of the tachycardia.     

Electrophysiologic characteristics of ventricular extrastimulation-induced dissipation of functional bundle branch block associated with supraventricular tachycardia

INTRODUCTION: Linking-related anterograde functional bundle branch block during supraventricular tachycardia (SVT) is due to repetitive concealed retrograde conduction of impulses from the contralateral bundle branch and can be eliminated by a critically timed premature ventricular beat (PVB). We assessed the electrophysiologic characteristics of PVB-induced dissipation of functional bundle branch block during SVT. METHODS AND RESULTS: During SVT with functional bundle branch block, PVB was delivered from the right ventricular apex, scanning the tachycardia cycle length (CL) with 10-msec decrements in the coupling interval in 14 patients (3 AV nodal reentrant tachycardia and 11 orthodromic AV reciprocating tachycardia). Dissipation was achieved in group 1: functional right bundle branch block (RBBB) in 4, functional left bundle branch block (LBBB) in 4, and both functional RBBB and LBBB in 1 with a dissipation zone occupying 4% to 13% (mean 8.5%) of the tachycardia CL. The outer limits were 22+/-16 msec and 68+/-14 msec < tachycardia CL; the inner limits were 56+/-18 msec and 90+/-24 msec < tachycardia CL for RBBB and LBBB, respectively (both P < 0.05). Dissipation could not be achieved in group 2 (4 RBBB and 1 LBBB) due to CL-dependent bundle branch block and/or local ventricular refractoriness. CONCLUSION: During SVT, functional bundle branch block due to "linking" often can be dissipated by timely PVB delivered from the right ventricular apex within a narrow zone of the tachycardia CL. Our findings suggest that the dissipation zone is affected by the pattern of functional bundle branch block relative to the site of PVB delivery.     

Radiofrequency catheter ablation for treatment of bundle branch reentrant ventricular tachycardia: results and long-term follow-up

Seven of 120 consecutive patients with inducible sustained ventricular tachycardia (from September 1, 1988 to January 1, 1991) had bundle branch reentrant tachycardia and underwent percutaneous radiofrequency ablation of the right bundle branch. The seven patients had been unsuccessfully treated with a mean of 3 +/- 1 drugs. Four patients presented with syncope and three with aborted sudden death. The baseline electrocardiogram revealed a left bundle branch block pattern in three patients and an intraventricular conduction defect in four. The baseline HV interval was prolonged in each case (79 +/- 2 ms). With use of programmed ventricular extrastimuli, sustained bundle branch reentrant tachycardia was inducible in all patients at a mean cycle length of 283 +/- 17 ms (range 230 to 350). Bundle branch reentrant tachycardia characteristics included atrioventricular dissociation, a His deflection that preceded each QRS complex and spontaneous His to His variation that preceded changes in ventricular tachycardia cycle length. A quadripolar catheter was positioned across the tricuspid valve with the distal electrode tip of the catheter near the right bundle branch. One to three applications of continuous unmodulated radiofrequency current at 300 kHz between the distal electrode and a large posterior skin patch resulted in complete right bundle branch block in all patients, after which none had inducible bundle branch reentrant tachycardia on restudy. On restudy, three of the seven patients had ventricular tachycardia of myocardial origin (not bundle branch reentry). One patient required no therapy; drug or defibrillator therapy was used in the others.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mahaim fiber: An atriofascicular or a long atrioventricular pathway?

There is debate concerning the distal insertion of Mahaim fibers. Some findings favor an atriofascicular fiber connected with the distal right bundle branch. Other findings favor a long atrioventricular (AV) structure inserting into the myocardium. A patient having a decrementally conducting accessory pathway is reported. Proximal and distal Mahaim potentials were recorded during sinus rhythm, atrial pacing, and antidromic tachycardia. Both proximal and distal M potentials always preceded the QRS complex during sinus rhythm and antidromic tachycardia earlier than the right bundle branch potential. During tachycardia, the distal M potential was recorded 6 ms before the retrograde right bundle potential. Other arguments consistent with an AV connection were a change in the QRS configuration during tachycardia after the first radiofrequency pulse at the site of the distal M potential and absence of right bundle branch block after successful ablation. Conduction through the proximal part of the Mahaim fiber was unaltered after ablation, as assessed by recording the proximal M potential. Electrophysiologic evidence is presented suggesting a long AV accessory pathway inserting close to the distal right bundle branch rather than an atriofascicular connection in this patient with a Mahaim fiber.     

Exercise-induced bidirectional ventricular tachycardia with alternating right and left bundle branch block-type patterns--a case report

Exercise-induced ventricular tachycardia in young adults may occur with various structural heart diseases or with structurally normal heart. The structural heart diseases reported to cause exercise-induced ventricular tachycardia in this patient population include arrhythmogenic right ventricular dysplasia, hypertrophic cardiomyopathy, dilated cardiomyopathy, myocarditis, congenital heart disease, and myocardial ischemia. The conditions well identified to cause exercise-induced ventricular tachycardia with structurally normal heart are congenital long-QT syndrome and familial polymorphic ventricular tachycardia. Exercise-induced ventricular tachycardia may display polymorphic, monomorphic, or bidirectional morphologies. A case of exercise-induced catecholamine-sensitive bidirectional ventricular tachycardia with alternating right and left bundle branch block patterns is reported in a young boy in the absence of structural heart disease, the conditions causing bidirectional ventricular tachycardia, and family history of such an event or sudden cardiac death. The bidirectional tachycardia typically displays right bundle branch block in right precordial leads with alternating polarity of the QRS-complex in frontal plane leads but in this case the bidirectional morphology of tachycardia was caused by alternating right and left bundle branch block-type patterns. The conditions causing bidirectional ventricular tachycardia are digoxin toxicity, ischemic heart disease, hypokalemia, myocarditis, and familial polymorphic ventricular tachycardia syndrome but the exact cause in this patient remained obscure, and the possibility of an underlying electrical or ion channel disease of the heart could not be ruled out.     

Verapamil‐sensitive Ventricular Tachycardia in an Infant

Patients. We report on a 6‐month‐old patient with a right bundle, superior axis tachycardia at 197 beats per minute. The tachycardia was unresponsive to adenosine, propranolol, flecainide, or amiodarone, or synchronized cardioversion. Overdrive atrial pacing terminated the tachycardia and since initiating verapamil, no recurrences of his tachycardia have occurred. Conclusions. If an infant presents with a right bundle, superior axis ventricular tachycardia unresponsive to multiple antiarrhythmic medications and synchronized cardioversion, but responsive to overdrive atrial pacing, one must consider verapamil‐sensitive ventricular tachycardia and initiate appropriate therapy.     

Automatic, implantible cardioverter-defibrillator in a patient with chronic Chagas cardiopathy and sustained ventricular tachycardia]

We studied a 48 years old woman, with chronic Chagasic cardiopathy, manifested with cardiomegaly, heart failure and syncope, due to a sustained ventricular tachycardia (SVT) of two different configurations (left bundle branch block and right bundle branch block). During electrophysiological testing, both types of ventricular tachycardia were reproduced. Successful ablation therapy of the right branch of His was performed due to suspicion of the bundle branch reentrant tachycardia, with a left bundle branch block. The patient continued to show SVT episodes, now with right bundle branch block pattern. Cardioverter Defibrillator was implanted. We report this case due to the rare frequency of Chagas' disease, where it could be a cause of heart disease, since the existence of the parasite (trypanosoma cruzi) and its vector (Triatoma) has been identified in some rural and suburban zones in the state of Aguascalientes, Mexico.     

Effects of right bundle branch block on the antidromic circus movement tachycardia in patients with presumed atriofascicular pathways

BACKGROUND: The typical and most common tachycardia in patients with atriofascicular pathways is a macro reentrant tachycardia, with anterograde conduction over the decrementally conducting bypass tract and retrograde conduction over the right bundle branch-His-AV node axis resulting in a short V-right bundle branch and short V-H interval. OBJECTIVES: To report on changes in rate and QRS configuration when right bundle branch block (RBBB) develops spontaneously during antidromic tachycardia using an atriofascicular fiber. METHODS: Three of 25 patients with an antidromic circus movement tachycardia using a right-sided atriofascicular pathway showed episodes of right bundle branch block (RBBB) during ventriculo-atrial conduction. Effect of retrograde RBBB on tachycardia rate and QRS configuration was studied using intracardiac and extracardiac recordings. RESULTS: All 3 patients showed prolongation of their V-A interval when retrograde RBBB occurred during tachycardia, resulting in a longer tachycardia cycle length. The VA time increase ranged from 85 to 100 msec, with a mean 346 +/- 5 msec. Two of the 3 patients also showed a change in QRS configuration due to a more leftward shift of the frontal plane QRS axis. CONCLUSION: Rate changes in antidromic tachycardia in patients with atriofascicular fibers can be based on a shift in VA conduction from one bundle branch to the other. This may be accompanied by changes in the frontal plane QRS axis because of a change in ventricular activation sequence.     

John B. Barlow: master clinician and compleat cardiologist

This paper reports the case of a 76‐year‐old man in whom atrial flutter with varying atrioventricular block and intermittent right bundle‐branch block was found. This is the first report on tachycardia‐dependent right bundle‐branch block associated with supernormal conduction in a case of atrial flutter. When an impulse is conducted to the ventricles beyond 0.72 s after a QRS complex of right bundle‐branch block configuration, the impulse falls after the abnormally long effective refractory period of the right bundle branch and passes through the right bundle branch. When the conducted impulse occurs within 0.72 s after a QRS complex of right bundle‐branch block configuration, the impulse usually falls in the refractory period and is blocked in the right bundle branch; however, only when the impulse occurs 0.48 or 0.49 s after that does it fall in the supernormal period and passes through the right bundle branch. The findings in the present report strengthen our previous suggestion that the presence of supernormal conduction plays an important role in the initiation of reentrant ventricular tachycardia.     

An unusual form of bundle branch reentrant tachycardia

INTRODUCTION: We report the case of a 36-year-old patient with a longstanding history of paroxysmal tachycardia. METHODS AND RESULTS: During the electrophysiological study, the H-V interval was prolonged in sinus rhythm, and a second potential (H') with distal to proximal activation pattern was recorded in the region of the proximal His-Purkinje system. Two wide QRS complex tachycardias were induced, both with V-A dissociation. One application of radiofrequency energy at the site with earliest and largest H' potential during sinus rhythm cured both tachycardias. The right and left bundle branch block morphology tachycardias were diagnosed as clockwise and counterclockwise bundle branch reentrant tachycardia. The H' potential represented the retrograde right bundle potential during sinus rhythm and bundle branch block reentrant tachycardia.     

Interesting case of narrow QRS tachycardia with atrioventricular dissociation

A 30-year-old man with no structural heart disease has been evaluated for paroxysmal palpitation with documented regular narrow QRS tachycardia that has not responded to intravenous adenosine. Surface electrocardiogram has not shown any pre-excitation. He has been taken for an electrophysiology study after informed consent. Diagnostic catheters were placed at the coronary sinus, His bundle region, and right ventricle. During catheter manipulation a regular narrow QRS tachycardia with incomplete right bundle branch block morphology and normal QRS axis similar to the clinical tachycardia got induced. No other tachycardia was induced. What is the mechanism of tachycardia?     

Ventricular tachycardia with QRS configuration similar to that in sinus rhythm and a myocardial origin: differential diagnosis with bundle branch reentry.

INTRODUCTION: Tachycardia with a QRS configuration which resembles that in sinus rhythm is usually thought to be supraventricular. Ventricular tachycardia, with a similar QRS configuration to that in sinus rhythm on the 12-lead ECG, can occur. The mechanisms of this form of ventricular tachycardia have not been previously reported. METHODS AND RESULTS: The mechanism of ventricular tachycardia was defined during electrophysiological study in five patients. During sinus rhythm, all patients had a wide QRS complex (>0.12 s) on the 12-lead ECG. The morphology remained grossly unchanged during spontaneous, symptomatic tachycardia. Four of the five patients had coronary artery disease and left ventricular dysfunction. The remaining patient had idiopathic dilated cardiomyopathy. The relationship between the His bundle, deflection, the right bundle branch and the QRS complex was evaluated during tachycardia. Atrial and ventricular pacing, and ventricular activation mapping were performed during tachycardia to define the tachycardia mechanism. The tachycardia induced at electrophysiological testing, which was similar to the clinical tachycardia, was proven to be ventricular tachycardia in each patient. The morphology of ventricular tachycardia was right bundle branch block in two patients and left bundle branch block in three patients. The median tachycardia cycle length was 300 ms (range: 260-480 ms). His bundle activation occurred in a 1:1 relationship with ventricular activation during tachycardia in all patients at least intermittently. The tachycardias were thought initially to be bundle branch reentry tachycardia. With further intervention and continued observation, it became clear that His bundle activation was passive and was not required for the tachycardia to sustain. During tachycardia, His bundle activation appeared to precede the local ventricular activation. Instead, the His bundle was activated slowly from the previous ventricular beat causing a long ventricular-His (VH) interval. This was shown by: (1) activation patterns, (2) response to pacing, (3) intermittent VH dissociation, and (4) termination of ventricular tachycardia. CONCLUSION: A unique form of ventricular tachycardia is described. The QRS complex morphology on the 12-lead ECG during tachycardia was grossly similar to that during sinus rhythm. The His bundle activation was passive and occurred with a long activation time from the ventricle to the His bundle. Although it mimics usual bundle branch reentry, this form of ventricular tachycardia appears to be due to a different mechanism in which the His bundle is not obligatory for the continuation of the reentrant phenomenon.     

Idiopathic Left Ventricular Tachycardia with Left and Right Bundle Branch Block Configurations

Fascicular Tachycardia. Introduction : Idiopathic left ventricular tachycardia typically has a right bundle branch block configuration. The purpose of this case report is to demonstrate that idiopathic ventricular tachycardia arising in or near the left posterior fascicle also may have a left bundle branch block configuration.
Methods and Results : A 27-year-old woman underwent an electrophysiologic procedure because of recurrent, verapamil-responsive, wide QRS complex tachycardia. Two types of ventricular tachycardia (cycle lengths 330 to 340 msec) were reproducibly inducible, one with a right bundle branch block configuration and left-axis deviation that had been documented clinically, and the other with a left bundle branch block configuration and axis of zero. A Purkinje potential recorded at the junction of the left ventricular mid-septum and inferior wall preceded the ventricular complex by 40 msec in both tachycardias. A single application of ra-diofrequency energy at this site successfully ablated both ventricular tachycardias.
Conclusion : The findings of this case report demonstrate that idiopathic ventricular tachycardia arising in or near the left posterior fascicle may have a left bundle branch block configuration     

Complex arrhythmias in a patient with predominantly right ventricular cardiomyopathy

A 23-year-old man presented with ventricular tachycardia. The electrocardiogram revealed right bundle branch block plus right axis deviation. It also showed frequent episodes of asystole, 2: 1 sinuatrial block and couplets of left bundle branch block morphology. Electrophysiologic study demonstrated sinuatrial entrance block, with an HV interval of 65 msec. It was also possible to induce sustained ventricular tachycardia of left bundle branch block pattern with normal QRS axis. Subsequent investigations were consistent with the diagnosis of right ventricular cardiomyopathy with mild left ventricular involvement.