Mohammad R. Jazayeri

Sustained bundle branch reentry as a mechanism of clinical tachycardia

The incidence of sustained bundle branch reentrant (BBR) tachycardia as a clinical or induced arrhythmia or both continues to be underreported. At our institution, BBR has been the underlying mechanism of sustained monomorphic ventricular tachycardia in approximately 6% of patients, whereas mechanisms unrelated to BBR were the cause in the rest. Data gathered from 20 consecutive patients showed electrophysiologic characteristics that suggest this possibility. These include induction of sustained monomorphic tachycardia with typical left or right bundle branch block morphology or both and atrioventricular dissociation or ventriculoatrial block. On intracardiac electrograms, all previously published criteria for BBR were fulfilled, and in addition, whenever there was a change in the cycle length of tachycardia, the His to His cycle length variation produced similar changes in ventricular activation during subsequent complexes with no relation to the preceding ventricular activation cycles. Compared with patients with ventricular tachycardia due to mechanisms unrelated to BBR, patients with BBR had frequent combination of nonspecific intraventricular conduction defects and prolonged HV intervals (100% vs. 11%, p less than 0.001). When this combination was associated with a tachycardia showing a left bundle branch block pattern, BBR accounted for the majority compared with mechanisms unrelated to BBR (73% vs. 27%, p less than 0.01). The above finding in patients with dilated cardiomyopathy should raise the suspicion of sustained BBR because dilated cardiomyopathy was observed in 95% of the patients with BBR. Twelve of the 20 patients were treated with antiarrhythmic agents, and the other eight were managed by selective catheter ablation of the right bundle branch with electrical energy. Our data suggest that sustained BBR is not an uncommon mechanism of tachycardia; it can be induced readily in the laboratory and is amendable to catheter ablation by the very nature of its circuit. The clinical and electrophysiologic features outlined in this study should enable one to correctly diagnose this important arrhythmia.

Transcatheter electrical ablation of right bundle branch. A method of treating macroreentrant ventricular tachycardia attributed to bundle branch reentry.

The present study describes the clinical and electrophysiological characteristics of sustained bundle branch reentrant ventricular tachycardia treated with electrical ablation of the right bundle branch. Seven patients presented with syncopal episodes, and six of the seven had documented episodes of ventricular tachycardia. All patients had depressed left ventricular ejection fraction with cardiomegaly. Six of the seven had dilated cardiomyopathy in the absence of significant coronary disease. Twelve-lead electrocardiograms in all seven patients during sinus rhythm were remarkably similar; six demonstrated intraventricular conduction defect resembling left bundle branch block, and one showed left anterior fascicular block. All patients showed prolonged His-to-ventricle intervals during sinus rhythm. Sustained ventricular tachycardia (with atrioventricular dissociation) because of bundle branch reentry was induced in all patients during baseline electrophysiological study. The His-to-ventricle intervals during tachycardia were similar to those seen during sinus rhythm. Electrical ablation of the right bundle branch was accomplished in each patient with delivery of two electrical shocks (170-310 J) through electrode catheters. Right bundle branch block developed on their surface electrocardiogram immediately after the ablation. Follow-up electrophysiological studies showed no inducible ventricular tachycardia. Clinical follow-up showed no recurrence of syncope or ventricular tachycardia. From the data presented, the following can be concluded. First, right bundle branch ablation is a safe and promising means of treating ventricular tachycardia because of bundle branch reentry and can obviate the need for antiarrhythmic drug therapy and its frequent undesirable side effects. Second, there are common clinical and electrophysiological characteristics that are frequently seen in patients with this tachycardia, and the recognition of these common characteristics should alert the physician to a bundle branch reentrant mechanism of ventricular tachycardia.

Echocardiographic demonstration of decreased left ventricular dimensions and vigorous myocardial contraction during syncope induced by head-up tilt

Two-dimensional echocardiography was performed during a head-up tilt test in 11 control subjects (group I) and 18 patients with recurrent unexplained syncope. In four patients (group II), the head-up tilt test was negative at baseline and after isoproterenol infusion. Syncope was induced during baseline head-up tilt in nine patients (group III) and after isoproterenol challenge in five (group IV). The echocardiographic variables assessed were left ventricular end-systolic and end-diastolic areas and percent fractional shortening. At the end of head-up tilt, end-systolic area decreased by 4.5 +/- 1.3 and 3.0 +/- 1.2 cm2 in groups III and IV, respectively, compared with 0.5 +/- 0.7 and 0.2 +/- 0.1 cm2 in groups I and II, respectively (p less than 0.04). Similarly, end-diastolic area decreased by 5.5 +/- 2.6 cm2 in group III compared with 2.7 +/- 1.9 and 1.75 +/- 0.4 cm2 in group I and II, respectively (p less than 0.04). Additionally, at the end of the baseline study, fractional shortening was significantly greater in group III and group IV (43 +/- 5%) than in groups I and II (p less than 0.01). In conclusion, syncope induced by head-up tilt is associated with vigorous myocardial contraction and a significant decrease in left ventricular end-systolic dimensions. This left ventricular hypercontractility may play an important role in the pathogenesis of syncope induced by head-up tilt.

Localization of the fast and slow pathways in atrioventricular nodal reentrant tachycardia by intraoperative ice mapping.

BackgroundAtrioventricular (AV) nodal reentrant tachycardia is classically described as a reentrant rhythm entirely contained within the compact AV node. Although the concepts of longitudinal dissociation of two intranodal pathways and a distal common pathway are accepted, the proximal portion of the circuit remains undefined. Current reports suggest that the two pathways may be separable by atrial tissue and not contained entirely within the compact node. Methods and ResultsWe used an ice mapping method to demonstrate the slow and fast pathways of the reentrant circuit and their relation to the atrial septum around the AV node. Six patients with the usual form (slow-fast) of AV nodal reentrant tachycardia were mapped during surgery. In most patients, antegrade slow pathway localization was posterior and inferior to the compact AV node along the tricuspid annulus; in two patients, it was superior along the tendon of Todaro. Retrograde fast pathway localization was anterior or superior to the compact AV node in all patients. In all patients, anatomic distinction was made between the two pathways and the compact node. ConclusionsWe conclude that no upper common pathway exists within the compact AV node in the usual type of nodal reentrant tachycardia and that the perinodal atrial tissue is a requisite part of the tachycardia circuit.

Useful clinical criteria for the diagnosis of ventricular tachycardia

Misdiagnosis occurs upon initial presentation to medical attention in a considerable number of patients referred for evaluation of wide QRS tachycardia. In order to improve diagnostic accuracy (ventricular versus supraventricular tachycardia), the answers to two key bedside questions were prospectively evaluated: (1) Had the patient experienced a prior myocardial infarction? (2) Did symptoms of tachyarrhythmia start only after the infarction? A patient presenting with a wide QRS tachycardia was considered to have ventricular tachycardia if he or she answered in the affirmative to both of these questions. Of 31 consecutive patients referred with electrocardiographically documented sustained wide QRS tachycardia that was reproduced in the electrophysiology laboratory, the diagnoses made when the patients first presented to medical attention were ventricular tachycardias in 17 patients and supraventricular tachycardias in 14 patients. Following electrophysiologic evaluation, 29 were diagnosed as having ventricular tachycardia and two as supraventricular tachycardia. If the diagnoses were made solely on the basis of responses to the bedside questions mentioned earlier, 28 of the 29 patients having a final diagnosis of ventricular tachycardia would have been correctly identified. It is concluded that the use of these two questions can be very helpful in improving the clinical diagnosis of ventricular tachycardia.

Spontaneous Reinitiation of Atrial Fibrillation Following Transvenous Atrial Defibrillation

Spontaneous reinitiation of atrial fibrillation (AF) has not been systematically looked at in patients undergoing transvenous AF. This study involved 11 patients, the mean age 60 ± 8 years. 3 male and 8 female, in whom transvenous atrial defibrillation successfully converted AF to sinus rhythm. Eight patients had paroxysmal AF and three patients had chronic persistent AF for 4 weeks or more. Four patients were taking antiarrhythmic medications at the time of testing. Multipolar transvenous catheters were positioned inside the coronary sinus, right atrium, and the right ventricle. Atrial defibrillation testing was performed using the METRIX atrial defibrillation system in nine patients and the Ventritex HVSO2 in the remaining two patients. A total of 64 therapeutic shocks (range 3–11) were delivered in the 11 patients, and 31 of these successfully converted AF to sinus rhythm. In four patients spontaneous AF was reinitiated following 12 successful transvenous atrial defibrillation episodes. The mean time to reinitiation of AF following shock delivery and restoration of sinus rhythm was 8.26 ± 5.25 seconds, range 1.8–19.9 seconds. All 12 episodes of spontaneous AF were preceded by a spontaneous premature atrial complex. The coupling interval of the premature atrial complexes was 443 ± 43 ms, range 390–510 ms. None of the patients taking antiarrhythmic medications or those demonstrating no premature atrial complexes had spontaneous reinitiation of AF. In conclusion, spontaneous reinitiation of AF can occur in a significant proportion of patients with AE undergoing transvenous atrial defibrillation. This phenomenon is preceded by the occurrence of atrial premature complex. Findings of this study may have significant clinical implications.(PACE 1998; 21:1105–1110)

Psychological Support and Psychiatric Management of Patients with Automatic Implantable Cardioverter Defibrillators

There are well over 6, 000 automatic implantable cardioverter defibrillators (AICD) that have been implanted in the United States since 1980. The device clearly reduces arrhythmic mortality in high risk patients. Many AICD patients have other cardiac diseases, most commonly, coronary artery disease with associated prior myocardial infarctions. These patients have special psychosocial stresses that may make them vulnerable to depression and other psychological disturbances. Psychological support together with psychiatric treatment, if needed, should be provided to these patients. Use of psychotropic medications should be closely monitored, especially in this population, as many of these drugs can exacerbate ventricular tachyarrhythmias. Special precautions should also be taken when administering electroconvulsive therapy in these patients.

Efficacy of cryosurgery alone for refractory monomorphic sustained ventricular tachycardia due to inferior wall infarction.

The efficacy of cryosurgery alone was evaluated in 15 patients with refractory monomorphic sustained ventricular tachycardias related to inferior wall infarction. Patients were 64 +/- 9 (SD) years old and had a mean left ventricular ejection fraction of 39.2 +/- 11.2%. Thirty different tachycardias were mapped with the origin localized to the septum or inferior wall in 20 (67%), near the mitral valve anulus in 6 (20%) and at the base of the posterior papillary muscle in 4 (13%) tachycardias. Endocardial cryoablation of these sites was performed with 6 to 13 (mean 9.2 +/- 1.8) cryolesions per heart. No mitral valve replacement was performed. There was one postoperative death as a result of sepsis. Cryoablation abolished inducible ventricular tachycardia in 11 patients. Of the other three patients, the tachycardia in two was controlled with a single antiarrhythmic agent that had previously failed to suppress inducible ventricular tachycardia. Thus, clinical success was obtained in 13 (93%) of 14 patients. The remaining patient received an automatic implantable cardioverter defibrillator. Ejection fraction remained unchanged or improved after surgery in 14 patients (93%). There have been no late deaths, recurrence of sustained ventricular tachycardia or significant mitral regurgitation during a mean follow-up period of 19 +/- 7 months. These results compare quite favorably with those previously reported for subendocardial resection alone, and indicate that cryosurgery is highly effective, does not result in deterioration of left ventricular function and preserves mitral valve competence when cryoablation of the posterior papillary muscle is necessary.

When is it safe not to replace an implantable cardioverter defibrillator generator

In most reports on patients receiving implantable cardioverter defibrillators. shocks were received mainly during the first 2 to 3 years. Thus, the question had been raised as to the need for device replacement after 3 or 4 years if no shocks had been received. In order to answer this question, shock experience in 184 putients receiving the implantable cardioverter defibrillator was analyzed. Patients were followed for a mean of 24 ± 18.7 months. A patients shock was judged to be appropriate if there was electrocardio‐graphic documentation of sustained ventricular tachyarrhythmia at the time of shock or if it was preceded by sudden onset of presyncopal or syncopal symptoms. The majority of patients had coronary artery disease. In approximately two‐thirds of patients, left ventricular ejection fraction was below 40%. One hundred fourteen patients had inducible sustained monomorphic ventricular tachycardia. On follow‐up, there were 29 deaths, five of which were sudden. Sixty‐eight patients received an appropriate shock during follow‐up (37%). Over 90% of these 68 received their first shock within the 2 years after implant. The actuarial risk of receiving an appropriate shock by the fifth year after implant was 69%. Conversely, 31% of patients who survived 5 years had not received an appropriate shock. Hazard analysis indicates that there is a high incidence of first appropriate shock during the year following implant. Subsequently, the incidence dropped to a relatively steady rate with a rise in this rate during the fifth year. This analysis suggested a bimodal distribution of appropriate shocks. The results indicate that implantable cardioverter defibrillator generators should be replaced even up to the fifth year despite the fact that a patient had not received an appropriate shock.

Comparison of outcome of implantable cardioverter defibrillator implantation in patients with severe versus moderately severe left ventricular dysfunction secondary to atherosclerotic coronary artery disease.

This study was undertaken to assess the feasibility and clinical outcome of implantable cardioverter-defibrillators (ICDs) among patients with coronary artery disease and left ventricular ejection fraction (LVEF) of <20%. The morbidity, mortality, and the long-term survival of 117 patients with LVEF of <20% (group 1) were compared with 321 patients with LVEF of 20% to 40% (group 2). Mortality in the first 30 days after ICD implantation was 0% for group 1 and 0.6% in group 2. Actuarial survival (all cause) at the end of 2, 4, and 5 years were 83%, 70%, and 62%, respectively, in group 1 and 90%, 80%, and 71% in group 2 (p = 0.05). Fifty-five patients (47%) in group 1 and 126 patients (39%) in group 2 received appropriate shocks during follow up. Among the patients in group 1, the overall survival at 2 years after an appropriate shock from an ICD was 92% for patients <60 years of age, 77% for patients ages 60 to 69, and 53% for patients >70 years old. Although the overall survival of patients in group 1 was slightly lower compared with those in group 2, in a multivariate analysis, the EF was not an independent predictor of poor survival. The ICD can be implanted with acceptable operative morbidity and mortality in selected patients with LVEF of <20%.