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Biomedical subjects

B D Halperin

Publications and source records attributed to B D Halperin.

At least 19 recordsLinked to original sources
PubMed1998

Recipient to donor conduction of atrial tachycardia following orthotopic heart transplantation.

We report a case of atrial tachycardia in a 60-year-old male 8 years postorthotopic heart transplantation. At electrophysiology study, the clinical rhythm was found to arise from the remnant of the recipient atrium and was successfully terminated by delivery of radiofrequency energy. Surgical scars formed at the anastomosis of the recipient and donor atrium during the time of orthotopic heart transplantation are thought to electrically isolate the two areas. Although rarely recognized, dysrhythmias originating from the recipient atrial remnant may occur more often than previously thought.

Catheter Ablation↗
PubMed1997

Safety and efficacy of radiofrequency modification of slow pathway conduction in children < or = 10 years of age with atrioventricular node reentrant tachycardia.

This study evaluated procedural considerations, risks, and long-term efficacy of radiofrequency modification of slow pathway conduction for treatment of atrioventricular node reentrant tachycardia in children < or = 10 years of age. Using a combined anatomic and electrographic mapping approach, modification of slow pathway conduction was achieved in 25 consecutive patients, although 4 had some form of transient atrioventricular block, indicating the need for caution in patient selection, catheter manipulation, and ablation.

Adolescent↗
PubMed1997

The effect of electrode size on transvenous defibrillation energy requirements: a prospective evaluation.

Recent technological advances have resulted in high success rates for implantation of nonthoracotomy defibrillation lead systems. Further decreases in defibrillator size, facilitating pectoral placement, will depend in part on lowering defibrillation energy requirements. The purpose of this study was to determine if endocardial defibrillation energy requirements are influenced by electrode size. Thirteen adult mongrel dogs were studied under general anesthesia. A 9 Fr integrated bipolar pace/sense/defibrillation electrode (cathode) was positioned transvenously at the RV apex. The second defibrillation electrode (anode) was positioned at the junction of the RA and SVC. Two diameters of the proximal electrode, 7 Fr and 11 Fr, were sequentially tested in random order in each animal. The DFT for each electrode was determined using a 50-V up-down method. Energy, leading edge voltage, and current, current distribution, and total resistance were measured. The mean defibrillation voltage threshold with the 11 Fr proximal electrode was significantly less than with the 7 Fr proximal electrode (551.1 +/- 76.5 V vs 588.5 +/- 54.6 V, P < 0.01). Similarly, the mean DFT with the 11 Fr electrode was less than with the 7 Fr electrode (20.7 +/- 5.7 J vs 23.3 +/- 4.4 J, P < 0.01). Lower DFTs were found using the larger electrode in 11 of the 13 animals studied. However, there was no difference in defibrillation lead impedance between the two electrode systems. Endocardial defibrillation energy requirements may be lowered with a larger diameter proximal electrode. The mechanism by which this occurs may be due to a more even distribution of current gradients with the larger electrode. Determination of the optimal electrode size requires evaluation in humans, as this may allow further reduction in defibrillation energy requirements and defibrillator size.

Animals↗
PubMed1996

Multicenter comparison of truncated biphasic shocks and standard damped sine wave monophasic shocks for transthoracic ventricular defibrillation. Transthoracic Investigators.

BACKGROUND: The most important factor for improving out-of-hospital ventricular fibrillation survival rates is early defibrillation. This can be achieved if small, lightweight, inexpensive automatic external defibrillators are widely disseminated. Because automatic external defibrillator size and cost are directly affected by defibrillation waveform shape and because of the favorable experience with truncated biphasic waveforms in implantable cardioverter-defibrillators, we compared the efficacy of a truncated biphasic waveform with that of a standard damped sine monophasic waveform for transthoracic defibrillation. METHODS AND RESULTS: The principal goal of this multicenter, prospective, randomized, blinded study was to compare the first-shock transthoracic defibrillation efficacy of a 130-J truncated biphasic waveform with that of a standard 200-J monophasic damped sine wave pulse using anterior thoracic pads in the course of implantable cardioverter-defibrillator testing. Pad-pad ECGs were also examined after transthoracic defibrillation. After the elimination of data for 24 patients who did not meet all protocol criteria, the results from 294 patients were analyzed. The 130-J truncated biphasic pulse and the 200-J damped sine wave monophasic pulse resulted in first-shock efficacy rates of 86% and 86%, respectively (P = .97). ST-segment levels measured 10 seconds after the shock in 151 patients in sinus rhythm were -0.26 +/- 1.58 and -1.86 +/- 1.93 mm for the 130- and 200-J shocks, respectively (P < .0001). CONCLUSIONS: We found that 130-J biphasic truncated transthoracic shocks defibrillate as well as the 200-J monophasic damped sine wave shocks that are traditionally used in standard transthoracic defibrillators and result in fewer ECG abnormalities after the shock.

Adolescent↗
PubMed1996

Optimal electrode position for transvenous defibrillation: a prospective randomized study.

OBJECTIVES: This study was performed to determine the optimal position for the proximal electrode in a two-electrode transvenous defibrillation system. BACKGROUND: Minimizing the energy required to defibrillate the heart has several potential advantages. Despite the increased use of two-electrode transvenous defibrillation systems, the optimal position for the proximal electrode has not been systematically evaluated. METHODS: Defibrillation thresholds were determined twice in random sequence in 16 patients undergoing implantation of a two-lead transvenous defibrillation system; once with the proximal electrode at the right atrial-superior vena cava junction (superior vena cava position) and once with the proximal electrode in the left subclavian-innominate vein (innominate vein position). RESULTS: The mean (+/- SD) defibrillation threshold with the proximal electrode in the innominate vein position was significantly lower than with the electrode in the superior vena cava position (13.4 +/- 5.7 J vs. 16.3 +/- 6.6 J, p = 0.04). Defibrillation threshold with the proximal electrode in the innominate vein position was lower or equal to that achieved in the superior vena cava position in 75% of patients. In patients with normal heart size (cardiothoracic ratio < or = 0.55), the improvement in defibrillation threshold with the proximal electrode in the innominate vein position was more significant than in patients with an enlarged heart (innominate vein 13.0 +/- 6.5 J vs. superior vena cava 17.9 +/- 5.1 J, p < 0.01). In patients with an enlarged heart, no difference between the two sites was observed (innominate vein 13.9 +/- 4.5 J vs. superior vena cava 13.6 +/- 8.3 J, p = NS). CONCLUSIONS: During implantation of a two-lead transvenous defibrillation system, positioning the proximal defibrillation electrode in the subclavian-innominate vein will lower defibrillation energy requirements in the majority of patients.

Aged↗
PubMed1995

Use of adenosine to identify patients at risk for recurrence of accessory pathway conduction after initially successful radiofrequency catheter ablation.

OBJECTIVE: The use of adenosine after radiofrequency catheter ablation of accessory pathways was prospectively studied to determine its utility for identifying patients at risk for recurrence of accessory pathway conduction and to guide therapy that might reduce late recurrence in this group. BACKGROUND: Accessory pathway conduction recurs in 5%-12% of patients following initially "successful" radiofrequency catheter ablation. Adenosine may facilitate conduction over accessory pathways that have been modified by radiofrequency delivery, thus identifying patients at risk for recurrence. METHODS: Radiofrequency catheter ablation was performed in 109 patients. Prior to ablation, 12-18 mg of adenosine was administered. After ablation, when all evidence of accessory pathway conduction remained absent for at least 30 minutes, adenosine 12-18 mg was again administered. RESULTS: Adenosine given prior to radiofrequency catheter ablation did not block accessory pathway conduction in any patient. Adenosine given after elimination of accessory pathway conduction induced complete atrioventricular and ventriculoatrial block in 95 patients; 11 (11.6%) subsequently had recurrence of accessory pathway function. Accessory pathway conduction was unmasked by adenosine in 12 patients (11.2%). After further deliveries of radiofrequency energy, 7 of these 12 patients subsequently demonstrated adenosine induced atrioventricular and ventriculoatrial block; 1 of these 7 patients experienced recurrence of accessory pathway conduction. The remaining 5 patients demonstrated persistent accessory pathway conduction only with adenosine; all experienced clinical recurrence of accessory pathway function. CONCLUSION: The use of adenosine after presumed successful radiofrequency catheter ablation may reveal persistent accessory pathway conduction. Elimination of this latent accessory pathway conduction reduces the risk for recurrence.

Adenosine↗
PubMed1994

Comparison of radiofrequency catheter ablation procedures in children, adolescents, and adults and the impact of accessory pathway location.

Radiofrequency (RF) catheter ablation is an accepted treatment for supraventricular tachycardia. However, the determinants of success, difficulty, or risk of complication associated with ablation have not been defined. This study evaluated patient age and location of the accessory or extranodal pathway as determinants of these procedural variables. Patients were stratified by age, with those aged 2 to 12 years classified as children, those aged 13 to 19 years as adolescents, and those > or = 20 years as adults. Locations were defined as right, septal, or left free wall accessory pathways, or extranodal slow pathways associated with atrioventricular node reentrant tachycardia. A total of 443 RF ablation procedures performed in 413 patients were evaluated. All procedures were performed in the same laboratory by the same group of physicians. Success rates for ablation of supraventricular tachycardia did not differ among the 3 age groups, ranging from 93% to 95%. Procedural aspects, including total procedure time, fluoroscopy time, and number of applications of RF energy also did not differ by age group. However, analysis of outcome and procedural complexity with respect to pathway location demonstrated that ablation of right free wall and septal accessory pathways was significantly more difficult than left free wall or slow pathway (success rates of 85% and 88% vs 97% and 98%, respectively, p = 0.01 and 0.02), irrespective of age. Additionally, right free wall pathways required significantly greater procedure time (mean = 5.1 hours), fluoroscopy time (mean = 78 minutes), and RF applications (median = 16) than ablations performed at other sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Atypical forms of supraventricular tachycardia due to atrioventricular node reentry in children after radiofrequency modification of slow pathway conduction.

OBJECTIVES: This study was performed to investigate the prevalence, mechanisms and clinical significance of supraventricular tachycardias inducible in children or adolescents after radiofrequency modification of slow pathway conduction for the treatment of atrioventricular (AV) node reentrant tachycardia. BACKGROUND: Limited data have been reported with regard to the physiology of AV node reentrant tachycardia in young patients. Radiofrequency catheter ablation allows evaluation of the effects of selective modification of the different pathways involved in AV node reentrant tachycardia. METHODS: Selective modification of slow pathway conduction was performed in 18 young patients (12.9 +/- 3.4 years old) with typical (anterograde slow-retrograde fast) AV node reentrant tachycardia. Radiofrequency energy was applied across the posteromedial or midseptal tricuspid annulus, guided by slow pathway potentials and anatomic position. Programmed stimulation was performed after modification of slow pathway conduction defined as noninducibility of typical AV node reentrant tachycardia. RESULTS: Modification of slow pathway conduction was achieved in each patient, with a median of four applications of radiofrequency energy. However, atypical forms of supraventricular tachycardia were inducible in 9 of 18 young patients after slow pathway modification: AV node reentrant tachycardia with 2 to 1 AV block (seven patients); anterograde fast-retrograde slow AV node reentrant tachycardia (five patients); and sustained accelerated junctional tachycardia (two patients). In comparison, atypical forms of tachycardia were inducible in only 2 of 59 adult patients with AV node reentrant tachycardia undergoing slow pathway modification in the same laboratory (p = 0.01). Additional applications of radiofrequency energy to the posteromedial tricuspid annulus rendered AV node reentrant tachycardia with 2 to 1 block and the fast-slow form of AV node reentrant tachycardia noninducible. Junctional tachycardia terminated spontaneously in both patients. During 9.8 +/- 3 months of follow-up, slow-fast AV node reentrant tachycardia has recurred in one patient, whereas fast-slow AV node reentrant tachycardia has occurred in two patients, both with inducible fast-slow tachycardia after the initial modification of slow pathway conduction. CONCLUSIONS: Initial applications of radiofrequency energy may selectively modify the anterograde conduction of slow pathway fibers in young patients with AV node reentrant tachycardia. This may result in AV node reentrant tachycardia with 2 to 1 AV block or a reversal of the reentrant circuit (fast-slow tachycardia). Induction of these tachyarrhythmias indicates that further applications of radiofrequency energy are required for the successful modification of slow pathway conduction in young patients. The increased prevalence of inducible atypical arrhythmias among young patients suggests differences in the anatomic or electrophysiologic substrate of AV node reentrant tachycardia that may evolve as a function of age.

Adolescent↗
PubMed1994

Analysis of body surface area as a determinant of impedance during radiofrequency catheter ablation in adults and children.

Since most radiofrequency (RF) generators used for catheter ablation approximate a constant voltage output, applied power is inversely proportional to the impedance load of the system. Knowledge of the expected impedance load for a patient may facilitate selection of safer and more effective voltage output. Preliminary observations suggest that in adults, impedance is directly proportional to body surface area (BSA), thus prompting this study to determine whether this relation was maintained in smaller patients undergoing RF catheter ablation. Prospective analysis of impedance from 949 RF deliveries in 76 patients (BSA, 0.69-2.3 m2) revealed the mean impedance for all deliveries to be 103 +/- 8 ohms. Two-phase linear regression analysis revealed a significant, direct correlation between impedance and BSA in patients with a BSA > or = 1.5 m2 (P = .001); however, for patients with a BSA < 1.5 m2 there was no correlation. These results indicate that as patient size decreases below 1.5 m2, impedance is constant. Radiofrequency catheter ablation procedures in children may require selection of a voltage output similar to that used in adults in order to produce effective RF lesions.

Adult↗
PubMed1994

Early changes in defibrillation threshold following implantation of a nonthoracotomy system in dogs.

BACKGROUND: Nonthoracotomy systems are rapidly becoming the preferred surgical method for implantation of cardioverter defibrillators. Testing is performed at the time of implantation to insure an adequate margin of safety for defibrillation. However, this safety margin may change with lead maturation. This study evaluated changes in defibrillation threshold following implantation of a nonthoracotomy system. METHODS AND RESULTS: Ten dogs underwent implantation of a nonthoracotomy system consisting of a single catheter with a distal coil electrode in the right ventricular apex and a proximal coil electrode in the superior vena cava forming a common anode with a subcutaneous patch over the left thorax. Defibrillation threshold testing, using a biphasic waveform, was performed on each animal under general anesthesia at implantation (day 1) and subsequently on postoperative days 3, 7, 10, 17, 24, 31, 38, and 45. E50, the energy associated with a 50% likelihood of successful defibrillation, was determined at each setting. The mean E50 was 12.2 +/- 1.1 J at the time of implantation, increasing 36% to 16.8 +/- 2.0 J by day 38 (P < 0.01). Individual increases in E50 of 10-12 J were observed in four animals. CONCLUSIONS: Energy requirements for defibrillation with a nonthoracotomy system increase during the early postoperative period, with the highest defibrillation threshold observed at 38 days. This increase may be applicable to humans and should be considered when selecting an adequate energy safety margin for defibrillation at time of implantation.

Animals↗
PubMed1994

Mechanisms of AV node reentrant tachycardia in young patients with and without dual AV node physiology.

Recent advances in electrophysiological mapping and radiofrequency catheter ablation have demonstrated the participation of perinodal atrial tissue or pathways in atrioventricular node reentrant tachycardia (AVNRT). Current concepts of the role of these pathways in the genesis of the various forms of AVNRT continue to evolve. In view of these recent advances, this study investigated the electrophysiology of AVNRT in young patients, and factors potentially associated with variant forms of this arrhythmia. Detailed programmed stimulation and catheter mapping were performed in 35 consecutive young patients with AVNRT. This group consisted of 15 male and 20 female patients, with a mean age of 12.1 +/- 4.2 years (range 3-18 years). Of the 35 patients, 23 demonstrated dual AV node physiology, either in response to a critically timed extrastimulus (n = 17) or to rapid pacing (n = 6). The common form (antegrade slow-retrograde fast) of AVNRT was demonstrated in 21 of these 23 patients. Antegrade fast-retrograde slow (n = 1) and antegrade slow-retrograde slow (n = 1) forms of AVNRT were identified in the 2 other patients. In contrast, only 5 of the 12 patients who did not demonstrate dual AV node physiology had the common form of AVNRT (P = 0.03). Five of these patients also had the slow-slow form of AVNRT, while 1 patient each had a fast-slow and fast-fast form of AVNRT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Implantable cardioverter-defibrillator therapy in survivors of out-of-hospital sudden cardiac death without inducible arrhythmias.

OBJECTIVES: The aim of this study was to determine the efficacy of implantable cardioverter-defibrillator (ICD) therapy in survivors of sudden cardiac death in whom no ventricular arrhythmias can be induced with programmed electrical stimulation. BACKGROUND: Survivors of sudden cardiac death in whom ventricular arrhythmias cannot be induced with programmed electrical stimulation remain at risk for recurrence of serious arrhythmias. Optimal protection to prevent sudden death in these patients is uncertain. This study compares survival in the subset of survivors of sudden cardiac death with that of patients treated with or without an ICD. METHODS: A retrospective study was performed on 194 consecutive survivors of primary sudden death who had < or = 6 beats of ventricular tachycardia induced with programmed electrical stimulation with at least three extrastimuli. Ninety-nine patients received an ICD and 95 did not. RESULTS: There were no significant differences between the two groups in presenting rhythm, number of prior myocardial infarctions or use of antiarrhythmic agents. Patients treated with an ICD were younger (55 +/- 16 vs. 59 +/- 11 years, p = 0.03) and had a lesser incidence of coronary artery disease (48% vs. 63%, p = 0.04) and a lower ejection fraction (0.43 +/- 0.16 vs. 0.48 +/- 0.18, p = 0.04). There were no significant differences between the groups in the use of revascularization procedures or antiarrhythmic agents after the sudden cardiac death. Patients treated with an ICD had an improvement in sudden cardiac death-free survival (p = 0.04) but the overall survival rate did not differ from that of the patients not so treated (p = 0.91). A multivariate regression analysis that adjusted for the observed differences between the groups did not alter these results. CONCLUSIONS: Survivors of sudden cardiac death in whom no arrhythmias could be induced with programmed electrical stimulation remained at risk for arrhythmia recurrence. Although the proportion of deaths attributed to arrhythmias was lower in the patients treated with an ICD, this therapy did not significantly improve overall survival.

Actuarial Analysis↗
PubMed1993

Mechanical correlates of contraction-excitation feedback during acute ventricular dilatation.

OBJECTIVE: The purpose was to examine the mechanical correlates of the electrophysiological changes that occur during acute left ventricular dilatation. METHODS: Ten isolated, retrogradely perfused, ejecting rabbit hearts were studied. Left ventricular volume was adjusted by varying left atrial perfusion pressure. Left ventricular pressure was measured directly. Changes in left ventricular chamber dimensions at the level of an epicardial electrode were evaluated with two dimensional echocardiography and wall stress was calculated from these measures. Regional left ventricular electrophysiological properties were measured at two left atrial perfusing pressures. RESULTS: Increases in left atrial perfusion pressure resulted in significant increases in left ventricular end diastolic and end systolic pressures, epicardial and endocardial circumference, and wall stress. Only changes in diastolic wall stress correlated with changes in ventricular refractoriness (r = 0.69, p = 0.027). CONCLUSIONS: Left ventricular dilatation results in shortening of ventricular refractoriness in the isolated, ejecting rabbit heart. Regional changes in refractoriness are best correlated with changes in wall stress.

Acute Disease↗
PubMed1993

Unmasking accessory pathway conduction with adenosine-induced atrioventricular nodal block after radiofrequency catheter ablation.

Radiofrequency catheter ablation is very effective in eliminating conduction over accessory pathways in patients with Wolff-Parkinson-White syndrome. However, accessory pathway conduction recurs in approximately 5 to 9 percent of patients in the weeks to months following ablation. We describe two cases in which intravenous adenosine revealed persistent accessory pathway conduction after apparently successful ablation, thus providing an indication for the delivery of further ablative therapy. Adenosine may improve the long-term efficacy of radiofrequency catheter ablation of accessory pathways by manifesting latent accessory pathway conduction.

Adenosine↗
PubMed1992

Analysis of local electrogram characteristics correlated with successful radiofrequency catheter ablation of accessory atrioventricular pathways.

UNLABELLED: Due to the limited myocardial lesions produced by radiofrequency current, the ablation of accessory pathways (AP) requires precise localization of such connections. The purpose of this study was to ascertain which characteristic(s) of the local bipolar electrogram, recorded from the ablation and adjacent electrode immediately prior to the application of radiofrequency current, correlated with precision in localization adequate to permit AP ablation. Signal analysis was performed for 326 sets of electrograms preceding the attempted ablation of 107 APs in 100 consecutive patients. For 80 antegrade APs, the following variables were evaluated: (1) the presence or absence of an AP potential; (2) the local atrial-AP interval; (3) the local atrioventricular (AV) interval; and (4) the relationship between the onset of local ventricular depolarization and onset of delta wave of the surface electrocardiogram. For the 27 concealed APs, the following characteristics were evaluated: (1) the presence or absence of an AP potential; and (2) the local VA interval during reciprocating tachycardia or ventricular pacing. RESULTS: Antegrade APs: By statistical analysis, the best correlate of successful ablation of an antegrade AP was a local AV interval less than or equal to 40 msec (positive predictive value = 94%; 95% confidence intervals [CI] = 81%-100%). Local AV intervals less than or equal to 50 msec preceded 88% of successful AP ablations, compared to only 8% of failed radiofrequency current applications. The positive predictive value of the other variables were: presence of an AP potential: 35% (95% CI = 27%-40%); local atrial-AP intervals less than or equal to 40 msec: 54% (95% CI = 43%-66%); and local ventricular depolarization preceding onset of the delta wave 43% (95% CI = 34%-52%). For concealed APs, the positive predictive value of a VA interval less than 60 msec was 71% (95% CI = 48%-88%); the positive predictive value for the presence of an AP potential was 58% (95% CI = 32%-81%). CONCLUSIONS: No single electrogram characteristic had a positive predictive value and a sensitivity greater than 90% for AP localization adequate for radiofrequency current ablation. For antegrade APs, the best correlate of adequate localization was a local AV interval less than or equal to 40 msec; as a corollary, radiofrequency current applications at sites where the local AV was greater than 60 msec, were unlikely to be effective. Objective criteria for the localization of concealed APs were less certain. Electrogram analysis, as a guide to AP localization and ablation, requires careful analysis of multiple variables, with analysis of the local AV interval a salient objective factor.

Adult↗
PubMed1990

Misdiagnosing ventricular tachycardia in patients with underlying conduction disease and similar sinus and tachycardia morphologies.

Six patients presented with wide-complex tachycardias with QRS morphologies similar to those seen on their electrocardiograms that showed normal sinus rhythms. During normal sinus rhythm, each patient had an underlying intraventricular conduction abnormality or bundle branch block. Despite the similarity of the QRS complexes to those seen during sinus rhythm, the tachycardias subsequently proved to be ventricular in origin in each patient. It is important not to misdiagnose these disorders as supraventricular tachycardia as an erroneous diagnosis may result in inappropriate management.

Aged↗