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Biomedical subjects

A E Epstein

Publications and source records attributed to A E Epstein.

At least 37 records · Page 2Linked to original sources
PubMed1998

Gross and microscopic pathological changes associated with nonthoracotomy implantable defibrillator leads.

BACKGROUND: Although the effects of epicardial implantable cardioverter-defibrillator (ICD) leads on underlying cardiac tissue have been reported, the gross and microscopic changes associated with endocardial ICD leads are less well described. This study describes the gross and microscopic changes associated with endocardial ICD leads in humans. METHODS AND RESULTS: The hearts from 8 patients were examined. At the time of ICD implantation, the patients' mean age was 47+/-11 years, and the left ventricular ejection fraction was 0.24+/-0.10. Four patients had ischemic heart disease, and 4 had dilated cardiomyopathy. Five hearts were examined after transplantation; 3, after death. The electrode-myocardial interfaces were characterized by intense endocardial fibrosis and were remarkably consistent. Each lead was encased by a ring of fibroelastic tissue, and there was fibrosis of the right ventricular myocardium adjacent to the leads. Fibrosis involved the tricuspid valve in 5 patients, and 1 had perforation of the valve by the lead. Microscopically, interstitial fibrosis was adjacent to each lead in the current path of ICD shocks. Acute cell injury was present only in the hearts that had received recent shocks. CONCLUSIONS: The ICD electrode-myocardial interface is characterized by intense fibrosis. The fibrosis associated with endocardial ICD leads and the cumulative acute damage produced by defibrillation discharges may explain changes in the defibrillation and pacing thresholds and the difficulty of lead extraction that can be encountered with transvenous ICD systems.

Adult↗
PubMed1998

Marked reduction in internal atrial defibrillation thresholds with dual-current pathways and sequential shocks in humans.

BACKGROUND: This study tested the ability of sequential shocks delivered through dual-current pathways to lower the atrial defibrillation threshold (ADFT) compared with a biphasic shock through a standard single-current pathway. METHODS AND RESULTS: Electrodes were positioned in the right atrial appendage (RA), left subclavian vein (LSV), proximal coronary sinus (CSos), and distal coronary sinus (DCS) in 14 patients with chronic atrial fibrillation (170+/-185 days). Using a step-up protocol, we compared ADFTs for a single-current pathway (RA-->DCS) that used a single 7.5/2.5-ms biphasic shock from a 150-microF capacitor with those for a dual-current pathway system (RA-->DCS followed by CSos-->LSV) using sequential 7.5/2.5-ms biphasic shocks with capacitor discharge waveforms for 150-microF and 600-microF capacitors. Both dual-current pathway configurations (2.0+/-0.4 J for 150-microF capacitance, 2.4+/-0.5 J for 600-microF capacitance) had a significantly lower ADFT than the single-current pathway (5.1+/-1.8 J). Whereas the dual-current pathway with 150-microF capacitor shocks had a significantly lower energy threshold, there was no statistical difference in terms of leading-edge voltage compared with the dual-current pathway with 600-microF capacitance shocks. There were no ventricular arrhythmias induced with appropriately synchronized shocks. CONCLUSIONS: For internal atrial defibrillation in humans, sequential biphasic waveforms delivered over dual-current pathways resulted in a markedly reduced (>50% reduction) ADFT compared with a single shock over a single-current pathway.

Adult↗
PubMed1997

Are more complex implantable cardioverter defibrillators associated with an increased mortality? Lessons learned from clinical trials.

We compared 1-year survival in patients receiving implantable cardioverter defibrillators (ICDs) that provide only shock therapy with more advanced ICDs that provide antitachycardia pacing, bradycardia pacing, low-energy cardioversion, and advanced detection algorithms. Outcome in patients with advanced-generation ICD systems was similar or improved compared with outcome in patients receiving ICDs with only monophasic shock.

Clinical Trials as Topic↗
PubMed1997

Influence of patient characteristics in the selection of patients for defibrillator implantation (the AVID Registry). Antiarrhythmics Versus Implantable Defibrillators.

The Antiarrhythmics Versus Implantable Defibrillators (AVID) trial is a prospective, randomized study of treatment for life-threatening ventricular arrhythmias. Patients who are eligible for the main trial but who are not enrolled for any reason are followed in a registry. The objective of the present study was to determine whether there are identifiable patient characteristics among these registry patients that may influence whether a patient is treated with an implantable defibrillator. The 914 patients in the registry were divided into 2 groups according to whether the primary treatment was an implantable defibrillator. The mean age of defibrillator patients was 60 years, compared with 65 years in the nondefibrillator group (p <0.001). Only 11.2% of defibrillator recipients were minorities, whereas the percentage of minorities in the nondefibrillator group was 18.7% (p <0.003). A history of recurrent ventricular fibrillation was more likely in the group treated with defibrillators (8.9% vs 4.4%, p <0.01), whereas a history of atrial fibrillation or diabetes mellitus were both significantly more likely in the nondefibrillator group. Among defibrillator patients, a higher proportion had ventricular fibrillation as the index arrhythmia; patients with ventricular tachycardia were significantly more likely to be treated without devices. In this prospective but nonrandomized cohort of patients treated for life-threatening ventricular arrhythmias, older age, minority status, and comorbidity reduced the chances that a patient would be treated with a defibrillator.

Aged↗
PubMed1997

Simultaneous use of an implanted defibrillator and ventricular assist device.

A left ventricular assist device was placed as a bridge to cardiac transplantation in a 51-year-old man with cardiogenic shock. Placement of the left ventricular assist device occurred 5 years after implantation of an implantable cardioverter/defibrillator. The implantable cardioverter/defibrillator discharged appropriately during ventricular assist device support to terminate episodes of sustained ventricular tachycardia without causing malfunction of the ventricular assist device.

Defibrillators, Implantable↗
PubMed1997

Hemodynamic effects of an irregular sequence of ventricular cycle lengths during atrial fibrillation.

OBJECTIVES: The aim of this study was to determine the independent hemodynamic effects of an irregular sequence of ventricular cycle lengths in patients with atrial fibrillation (AF). BACKGROUND: Atrial fibrillation may reduce cardiac output by several possible mechanisms, including loss of the atrial contribution to left ventricular filling, valvular regurgitation, increased ventricular rate or irregular RR intervals. This study was designed to evaluate the effects of an irregular RR interval, independent of the average ventricular rate, on cardiac hemodynamic data during AF. METHODS: Sixteen patients with AF were studied invasively. During intrinsically conducted AF (mean rate 102 +/- 22 beats/ min), the right ventricular apex electrogram was recorded onto frequency-modulated (FM) tape. After atrioventricular node ablation, the right ventricular apex was stimulated in three pacing modes in randomized sequence: 1) VVI at 60 beats/min; 2) VVI at the same average rate as during intrinsically conducted AF (102 +/- 22 beats/min); and 3) during VVT pacing in which the pacemaker was triggered by playback of the FM tape recording of the right ventricular apex electrogram previously recorded during intrinsically conducted AF (VVT 102 +/- 22 beats/min). RESULTS: Compared with VVI pacing at the same average rate, an irregular sequence of RR intervals decreased cardiac output (4.4 +/- 1.6 vs. 5.2 +/- 2.4 liters/min, p < 0.01), increased pulmonary capillary wedge pressure (17 +/- 7 vs. 14 +/- 6 mm Hg, p < 0.002) and increased right atrial pressure (10 +/- 6 vs. 8 +/- 4 mm Hg, p < 0.05). CONCLUSIONS: An irregular sequence of RR intervals produces adverse hemodynamic consequences that are independent of heart rate.

Adult↗
PubMed1997

Pacing threshold increase in nonthoracotomy implantable defibrillator leads: implications for battery longevity and margin of safety.

Just as a stable defibrillation threshold is required for implantable defibrillators to maintain efficacy and a margin of safety for the conversion of life-threatening ventricular arrhythmias, a stable pacing threshold is also required to provide bradycardia support and pacing to terminate ventricular tachycardias. This article reports the temporal course of pacing thresholds in patients treated with a tripolar, tined endocardial defibrillator lead capable of bipolar sensing and pacing, and defibrillation. Seventeen patients who underwent implantation of an implantable defibrillator system using an integrated bipolar pacing/sensing system were prospectively studied over 18 months. There were 16 males and one female, with a mean age of 69 +/- 5 years (range 61-75 years). At implantation, predischarge, and every 2 months thereafter, the pacing pulse-width threshold was tested at both 2.5 and 5.0 V stimulus amplitudes. After a mean follow-up of 363 +/- 173 days (range 34-597 days), the pacing threshold increased from 0.08 +/- 0.08 ms to 0.5 +/- 0.3 ms at the 2.5 V amplitude (p < or = 0.01, CI-0.57 to -0.27) and from 0.04 +/- 0.02 ms to 0.25 +/- 0.14 ms at the 5.0 V amplitude (p < or = 0.01, CI -0.28 to -0.14). Eight of the 17 patients (47%) received spontaneous implantable defibrillator shocks for clinically detected arrhythmias, and the total number of joules delivered via the leads did not correlate with the pacing threshold changes. We conclude that the pacing threshold for the nonthoracotomy implantable defibrillator lead system studied is not stable and increases with time. This finding has implications for defibrillator battery life in patients who use implantable defibrillators for bradycardia pacing.

Aged↗
PubMed1997

A prospective, randomized evaluation of a nonthoracotomy implantable cardioverter defibrillator lead system. Endotak/PRX Investigator Group.

Nonthoractomy lead systems for ICDs have been developed that obviate the need for a thoracotomy and reduce the morbidity and mortality associated with implantation. However, an adequate DFT cannot be achieved in some patients using transvenous electrodes alone. Thus, a new subcutaneous "array" electrode was designed and tested in a prospective, randomized trial that compared the DFT obtained using monophasic shock waveforms with a single transvenous lead alone that has two defibrillating electrodes, the transvenous lead linked to a subcutaneous/submuscular patch electrode, and the transvenous lead linked to the investigational array electrode. There were 267 patients randomized to one of the three nonthoracotomy ICD lead systems. All had DFTs that met the implantation criterion of < or = 25 J. The resultant study population was 82% male and 18% female, mean age of 63 +/- 11 years. The indication for ICD implantation was monomorphic VT in 70%, VF in 19%, monomorphic VT/VF in 6%, and polymorphic VT in 4% of the patients, respectively. The mean LVEF was 0.33 +/- 0.13. The mean DFT obtained with the transvenous lead alone was 17.5 +/- 4.9 J as compared to 16.9 +/- 5.5 J with the lead linked to a patch electrode (P = NS), and 14.9 +/- 5.6 with the lead linked to the array electrode (array versus lead alone, P = 0.0001; array versus lead/patch, P = 0.007). The results of this investigation suggest that the subcutaneous array may be superior to the standard patch as a subcutaneous electrode to lower the DFT and increase the margin of safety for successful nonthoracotomy defibrillation.

Defibrillators, Implantable↗
PubMed1996

Classification of death in antiarrhythmia trials.

OBJECTIVES: We sought to develop and apply a new scheme for the classification of death to be used in trials of antiarrhythmia treatments. BACKGROUND: Because presently accepted classifications of death do not fully describe or tabulate all significant aspects of terminal events, nor do they consider unique aspects of arrhythmia investigations, a new classification scheme that addresses these issues is desirable. METHODS: A classification scheme of deaths that occur in antiarrhythmia trials was developed using the following categories: 1) primary organ cause (cardiac [arrhythmic, nonarrhythmic or unknown], noncardiac or unknown); 2) temporal course (sudden, nonsudden or unknown); 3) documentation (witnessed, monitored [yes, no or unknown]); 4) operative relation (preoperative, perioperative or postoperative); and 5) system relation (procedure related, pulse generator related and lead related [yes, no or unknown]). RESULTS: The classification scheme was used in a clinical trial of a new implantable cardioverter-defibrillator (1,250 patients, of whom 79 died) and used in an application for device market approval. Application of the classification to data reported using an older classification scheme is demonstrated. CONCLUSIONS: We propose a descriptive classification scheme that 1) fully describes and tabulates all significant aspects of terminal events; 2) incorporates previously used categorizations of death and new categorizations that address unique aspects of arrhythmia investigations; and 3) tabulates sufficient data to allow comparison with other studies. Events in a clinical trial of implantable defibrillator therapy were classified using the new classification scheme.

Arrhythmias, Cardiac↗
PubMed1996

The management of atrial fibrillation.

Atrial fibrillation affects approximately one million persons in the United States, making it the most common cardiac arrhythmia seen in clinical practice. Its prevalence increases with age, and occurs in up to 10% of the population in the eighth decade of life. Unlike coronary heart disease, atrial fibrillation affects men and women approximately equally and, in an increasingly elderly population, will become an increasing burden to the health care system. The management of atrial fibrillation has undergone significant change in recent years. Large randomized controlled trials have shown that anticoagulation markedly reduces the risk of stroke, and a number of new antiarrhythmic agents are available for the restoration and maintenance of sinus rhythm. Furthermore, physicians have become more aware of the potential proarrhythmic side effects of all antiarrhythmic drugs. Finally, new procedures such as radiofrequency ablation of the atrioventricular junction and permanent pacing are playing increasing roles in the management of this arrhythmia. In this review, the identification of underlying causes and/or precipitating factors of atrial fibrillation, methods to control the ventricular response with atrioventricular nodal blocking drugs, the questions of whether restoration of sinus rhythm is a possible or desirable goal and how best to maintain sinus rhythm, should sinus rhythm be restored, and the importance of long-term anticoagulation with warfarin or antiplatelet therapy with aspirin are discussed.

Anti-Arrhythmia Agents↗
PubMed1996

Posterior left thoracic cardiac sympathectomy by surgical division of the sympathetic chain: an alternative approach to treatment of the long QT syndrome.

Although high thoracic left sympathectomy via an anterior surgical approach is a highly efficacious treatment for refractory ventricular arrhythmias in patients with the long QT syndrome, the degree of sympathetic denervation has been variable, success of the operation is influenced by anatomical differences between patients, and Horner's syndrome may result. We hypothesized that interruption of sympathetic input to the heart could be accomplished using a posterior thoracic approach to this variable and often complex anatomy by division of the sympathetic chain rather than by direct destruction of the stellate and superior thoracic ganglia with the more conventional anterior, supraclavicular approach. In addition, the posterior approach should decrease the risk of Horner's syndrome by avoiding the ocular sympathetic efferent nerves. This posterior approach is described in five patients with the long QT syndrome and recurrent ventricular arrhythmias. After a mean follow-up of 18 +/- 12 months, all are alive without Horner's syndrome.

Adult↗