Zalmen Blanck

Bundle branch reentrant ventricular tachycardia: cumulative experience in 48 patients.

Sustained Bundle Branch Reentrant Tachycardia. introduction: The clinical, electrophysiologic features and follow‐up of 48 patients with inducible bundle branch reentrant (BBR) tachycardia are presented.

Atrioventricular nodal reentry. Clinical, electrophysiological, and therapeutic considerations.

BackgroundAtrioventricular (AV) nodal reentry is a relatively common cause of regular, narrow QRS tachycardia. The underlying basis for this arrhythmia is functional (and anatomic) duality of pathways in the region of the AV node, although the exact boundaries of the reentrant circuit have not been convincingly defined. During the more common type of AV nodal reentry (seen in approximately 90% of cases), a slow conducting pathway is used in the anterograde direction, and a fast pathway is operative in the retrograde direction. In the uncommon form, the direction of impulse propagation within the reentrant circuit is reversed. In this article, the clinical, ECG, and electrophysiological features of AV nodal reentry as well as approaches to therapy are discussed. Methods and ResultsClinical diagnosis may be made from the surface ECG. In the common type ofAV nodal reentry, the P wave is obscured by the QRS or may be present in its terminal portion. The P wave in the uncommon form occurs late (i.e., in or after the T wave), producing a pattern of long RP and short PR. Both forms of AV nodal reentry are controllable with various therapeutic modalities. For acute termination, adenosine is probably the ideal agent. Prevention of recurrences can be achieved with several pharmacological agents, including 1-blockers, calcium channel blockers, and class Ia, Ic, and III antiarrhythmic agents. Curative therapy is now available with a variety of nonpharmacological methods. However, the most promising therapy at the present time is catheter modification of the AV node by ablation of either the fast or slow pathway, using radiofrequency energy. Ablation of the fast pathway carries a higher risk of second- or third-degree AV block. Slow pathway ablation, by providing a high rate of success and minimal risk of AV block, seems to be a more acceptable initial approach. ConclusionsAV nodal reentry is a common cause of paroxysmal supraventricular tachycardia, and a precise diagnosis can be made with intracardiac electrophysiological evaluation. Although the arrhythmia responds to a variety of antiarrhythmic agents, curative therapy can now be offered with catheter modification of the AV node using radiofrequency energy. At the time of this writing, it seems that catheter modification of the AV node is rapidly becoming the therapy of initial choice in patients with symptomatic AV nodal reentrant tachycardia requiring treatment.

Provocation of Hypotension During Head-Up Tilt Testing in Subjects With No History of Syncope or Presyncope

BACKGROUND Head-up tilt test is increasingly being used to evaluate patients with syncope. This study was designed to evaluate the specificity of head-up tilt testing using different tilt angles and isoproterenol infusion doses in normal volunteers with no prior history of syncope or presyncope. METHODS AND RESULTS One hundred fifty volunteers were randomized to two groups of 75 each. In group 1, subjects were further randomized to have head-up tilt testing at a 60, 70, or 80 degree angle at baseline followed by repeat tilt testing during a low-dose isoproterenol infusion that increased the heart rate by an average of 20%. In group 2, after having a baseline head-up tilt test at a 70 degree angle for a maximum of 20 minutes, subjects were randomized to have a repeat tilt table testing at a 70 degree angle during a low-dose, 3 micrograms/min, or 5 micrograms/min isoproterenol infusion. In group 1, syncope or presyncope along with hypotension developed in 2 subjects during the baseline test at 60 and 70 degrees of tilt and in 5 subjects during tilting at 80 degrees. The addition of low-dose isoproterenol reduced the specificity minimally from 92% to 88% at both 60 and 70 degrees of tilt but substantially to 60% at an 80 degrees angle. However, 6 of the 10 subjects with a positive test at an 80 degree angle had an abnormal response after 10 minutes of tilt testing. In group 2, using various isoproterenol doses with tilt table testing at a 70 degree angle, low-dose (mean infusion dose, 1.5 +/- 0.45 microgram/min), 3 micrograms/min, and 5 micrograms/min isoproterenol infusions elicited an abnormal response in 1 (4%), 5 (20%), and 14 (56%) of the subjects, respectively. Using multiple logistic regression analysis, head-up tilt testing at an 80 degree angle (P = .01) or during 3 micrograms/min (P = .02) and 5 micrograms/min isoproterenol infusion rates (P < .001) was the most significant predictor of an abnormal response. CONCLUSIONS Head-up tilt testing at a 60 or 70 degree angle with or without low-dose isoproterenol infusion provides an adequate specificity. Caution is needed, however, in interpreting the results if the head-up tilt test at 80 degrees is extended beyond 10 minutes or if high doses of isoproterenol are used.

Computed Tomography‐Fluoroscopy Image Integration‐Guided Catheter Ablation of Atrial Fibrillation

Introduction: This study examines the feasibility of atrial fibrillation (AF) ablation using registered three‐dimensional computed tomography (CT) images of the left atrium with fluoroscopy.

Bundle branch reentry : a mechanism of ventricular tachycardia in the absence of myocardial or valvular dysfunction

OBJECTIVES The aim of this study was to present bundle branch reentry as the mechanism of sustained ventricular tachycardia in the absence of myocardial or valvular dysfunction. BACKGROUND Previous reports have documented the relation between structural heart disease and bundle branch reentrant ventricular tachycardia. Myocardial or valvular dysfunction has thus far been recognized as the only anatomic substrate for the development of this tachycardia. METHODS Three patients with a wide QRS complex tachycardia underwent noninvasive and invasive cardiac evaluation and electrophysiologic studies to identify the substrate and mechanism of tachycardia. Catheter ablation of the right bundle branch using radiofrequency current was performed in each patient. RESULTS The patients were all men (aged 54, 34 and 72 years) who presented with presyncope, palpitation and cardiac arrest, respectively. Electrocardiography during sinus rhythm revealed nonspecific intraventricular conduction delay in all three patients. Cardiac evaluation revealed no evidence of myocardial or valvular dysfunction in any patient. The baseline HV interval was prolonged in each patient (90, 100 and 75 ms, respectively). Programmed right ventricular stimulation initiated bundle branch reentrant tachycardia with typical left (three patients) and right (one patient) bundle branch block pattern. Catheter ablation of the right bundle branch using radiofrequency current abolished bundle branch reentry in all three patients. After 26-, 13- and 8-month follow-up periods, complete right bundle branch block persisted, and all three patients remained asymptomatic without antiarrhythmic drugs. CONCLUSIONS Sustained bundle branch reentry can be a clinical arrhythmia in patients with no identifiable myocardial or valvular dysfunction except for isolated conduction abnormalities in the His-Purkinje system. This mechanism of tachycardia should be recognized during electrophysiologic evaluation, given the seriousness of this arrhythmia and the availability of the effective treatment.

Ventricular Tachycardia in Valvular Heart Disease Facilitation of Sustained Bundle-Branch Reentry by Valve Surgery

BACKGROUND The clinical characteristics of sustained monomorphic ventricular tachycardia (SMVT), when it develops after valve surgery, have not been described. METHODS AND RESULTS Between 1985 and 1996, 31 patients (30 men and 1 woman) who had undergone valve surgery were found to have inducible SMVT. Nine patients (29%) had sustained VT due to bundle-branch reentry (BBR) (group 1). Four of these patients had normal left ventricular function, and VT with a right bundle-branch morphology was inducible in 4 patients. Group 2 included 20 patients with inducible myocardial (ie, non-BBR) VT. Coronary artery disease was present in 15 group 2 patients (75%) due to atherosclerotic (n=12) and nonatherosclerotic (n=3) causes. Two patients had both inducible sustained BBR and myocardial VT (group 3). Sustained BBR VT occurred significantly earlier after valve surgery (median, 10 days) than the onset of postoperative myocardial VT (median, 72 months; P<.005). CONCLUSIONS Myocardial VT was the most common type of inducible SMVT in patients with valvular heart disease. The majority of these patients had underlying coronary artery disease and significant left ventricular dysfunction. However, in almost one third of the patients, sustained BBR VT was the only type of inducible SMVT. This type of VT was facilitated by the valve procedure occurring within 4 weeks after surgery in most patients. In these patients, left ventricular function was relatively well preserved, and the right bundle-branch block type of BBR was frequently induced. Because a curative therapy can be offered to these patients (ie, bundle-branch ablation), BBR should be seriously considered as the mechanism of VT in patients with valvular heart disease, particularly if the arrhythmia occurs soon after valve surgery.

Efficacy of the Implantable Cardioverter-Defibrillator in the Elderly

OBJECTIVES We sought to assess the effect of advanced age on the outcome of patients with an implantable cardioverter-defibrillator (ICD). BACKGROUND ICDs are effective in preventing sudden cardiac death in susceptible patients, but their beneficial effect on survival is attenuated by the high rate of nonsudden cardiac death in those treated. Although advanced age is an important variable in determining cardiovascular mortality, its impact on the outcome of patients with an ICD has been inadequately studied. METHODS We performed multivariate analysis of a data base consisting of 769 consecutive patients with an ICD. Seventy-four patients > or = 75 years old at ICD implantation (Group 1) were compared with the remaining 695 patients (Group 2). RESULTS The two groups were similar in clinical presentation, left ventricular function and gender distribution. The mean follow-up time was 29 and 42 months, respectively, for patients in Group 1 and Group 2. Actuarial survival at 4 years was 57% in Group 1 versus 78% in Group 2 (p = 0.0001). This difference was primarily due to a higher rate of nonsudden cardiac death in Group 1. On multivariate analysis, age > or = 75 years, New York Heart Association functional class III, left ventricular ejection fraction < 30% and appropriate shocks during follow-up were independently associated with increased mortality (odds ratio 3.56, 1.8, 1.6 and 1.39, respectively). CONCLUSIONS Among patients with similar functional class and ejection fraction, the mortality risk is increased threefold in those > or = 75 years old at the time of ICD implantation. Extrapolation of results from younger patients is likely to overestimate ICD benefit in the elderly.

Efficacy of Different Treatment Strategies for Neurocardiogenic Syncope

Objectives: The purpose of this study was to evaluate the efficacy of different therapeutic approaches for patients with a history of syncope and positive head‐up tilt testing. Background: Head‐up tilt testing has gained broad acceptance as a reliable diagnostic method for the assessment of patients with recurrent unexplained syncope. However, once the diagnosis is established, there is no consensus on the most appropriate treatment. In this respect, efficacy of drug therapy in preventing recurrence of symptoms in such patients is not entirely clear, and controversies exist regarding the need to confirm the effects of pharmacological interventions. Methods: Clinical follow‐up was obtained in 303 patients with a history of syncope and positive head‐up tilt testing. After the diagnostic head‐up tilt, patients were assigned to different therapeutic approaches according to their preference or logistic impediments. Of 303 patients, 44 received empiric therapy, 210 were treated with medications proven effective during repeated head‐up tilt testing, and 49 refused or discontinued medical therapy. The three groups were similar with regard to age, sex, and clinical presentation. The mean follow‐up was 2.8 ±1.8 years. Among the patients treated according to head‐up tilt guided therapy, 130 were on beta blockers, 35 on theophylline, 10 on ephedrine, 31 on disopyramide, and 4 on miscellaneous regimens. Empiric treatment consisted of beta blockers in 37 of 44 patients and other drugs in the remaining patients. Results: During the follow‐up, recurrence of symptoms was experienced in 12 (6%) of the 210 patients receiving the head‐up tilt guided therapy, 16 (36%) of 44 in the empiric therapy group, and 33 (67%) of 49 in the no therapy group. Recurrence of symptoms in patients on empiric or no therapy was significantly more frequent as compared to the head‐up tilt guided therapy group (P<0.01). Conclusions: In patients with unexplained syncope and positive upright tilt testing, therapeutic strategies identified on the basis of response during head‐up tilt have a more positive impact on the recurrence of symptoms during follow‐up.

Characterization of Atrioventricular Nodal Behavior and Ventricular Response During Atrial Fibrillation Before and After a Selective Slow-Pathway Ablation

BACKGROUND The presence of atrioventricular nodal dual-pathway physiology in patients with atrioventricular nodal reentrant tachycardia (AVNRT) provides an opportunity to characterize the effect of a selective slow-pathway ablation on the ventricular rate during atrial fibrillation (AF). This may have important clinical implications for the nonpharmacological management of AF with a rapid ventricular rate. METHODS AND RESULTS Selective radiofrequency catheter ablation of the atrioventricular nodal slow pathway was performed with a stepwise approach in patients with documented sustained AVNRT. The AV nodal conduction properties and refractoriness and the ventricular rate during induced AF were assessed at baseline and under autonomic blockade before and after a selective slow-pathway ablation in 18 patients (mean age, 34 +/- 8 years). Sustained AVNRT was induced with a mean cycle length of 339 +/- 58 ms. A slow-pathway ablation was successfully achieved with 5 +/- 4 applications of radiofrequency energy. The shortest cycle length of 1:1 AV conduction and the AV nodal effective refractory period significantly prolonged after ablation (367 +/- 53 versus 403 +/- 55 ms, P < .0001, and 258 +/- 55 versus 292 +/- 74 ms, P < .05, respectively). Selective slow-pathway ablation significantly prolonged the mean (526 +/- 93 versus 612 +/- 107 ms, P < .0001), the shortest (378 +/- 59 versus 423 +/- 73 ms, P < .0001), and the longest (826 +/- 150 versus 969 +/- 226 ms, P < .01) cycle lengths of the ventricular response to AF. Significant slowing of the ventricular rate during AF occurred in 13 patients (72%), including all eight patients in whom AV nodal dual-pathway physiology was abolished. Five patients did not have a significant change in the ventricular rate during AF; a persistent dual AV nodal pathway physiology was demonstrable in four of these patients. Loss of dual-pathway physiology after ablation had a sensitivity of 77%, specificity of 80%, and positive predictive value of 91% for slowing the ventricular rate during AF. CONCLUSIONS In patients undergoing a slow-pathway ablation for control of AVNRT, selective slow-pathway ablation may cause a significant decrease in the ventricular rate during AF. These effects are primarily due to the prolongation of AV nodal conduction properties and refractory period of the residual AV nodal transmission system. These findings may have important therapeutic implications for the nonpharmacological treatment of AF, particularly in patients with underlying dual AV nodal physiology.

Distribution of atrial electrogram types during atrial fibrillation: Effect of rapid atrial pacing and intercaval junction ablation

OBJECTIVES This study examined the anatomic distribution types and possible determinant of atrial electrogram types during atrial fibrillation. BACKGROUND Different types of atrial electrograms during atrial fibrillation have been observed and classified, but their anatomic distribution patterns, determinants and potential usefulness in guiding future catheter ablation are unknown. METHODS Two animal models of atrial fibrillation were used: the sterile pericarditis model (n = 10) and the rapid atrial pacing model (400 beats/min for 6 weeks, n = 6). The atrial electrogram of atrial fibrillation and the atrial effective refractory period were obtained from multiple sites of the right and left atrium. In addition, decremental rapid atrial stimulation was applied to the site of shortest and longest atrial effective refractory periods until atrial fibrillation induction in a subgroup of nine dogs. Ablation of the intercaval junction was performed using the radiofrequency catheter technique in dogs with atrial fibrillation duration > 1 min. RESULTS In both models, organized atrial electrograms (type I) were predominantly observed at the left atrial sites and the right atrial appendage, whereas disorganized atrial electrograms (type III) were mainly observed at the right posterolateral atrium. The distribution of the atrial electrogram types closely followed that of the atrial effective refractory period, with the shortest atrial effective refractory period corresponding to organized atrial electrograms (type I) and the longest atrial effective refractory period corresponding to disorganized atrial electrograms (type III). The correlation of atrial electrogram type with the atrial effective refractory period was further demonstrated by the effect of rapid atrial stimulation. When rapid atrial stimulation was applied to the site with the shortest atrial effective refractory period, disorganized atrial electrograms were observed at sites with the longest atrial effective refractory period, whereas 1:1 atrial capture was still present at the stimulation site. Ablation of the intercaval junction made atrial fibrillation noninducible or tended to shorten the atrial fibrillation duration (from 26.4 +/- 24.2 to 8.8 +/- 22.6 min in the pericarditis group, p = 0.02, and from 33.7 +/- 29.2 to 12.1 +/- 23.8 min in the rapid pacing group, p = 0.09) but did not change the atrial electrogram types during atrial fibrillation. CONCLUSIONS Various types of atrial electrograms are present at different locations during atrial fibrillation. The atrial electrogram characteristics of atrial fibrillation at a specific location are related to the atrial effective refractory period, with short effective refractory periods associated with organized atrial electrograms and long effective refractory periods associated with disorganized electrograms.