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Biomedical subjects

D S Schwartzman

Publications and source records attributed to D S Schwartzman.

6 recordsLinked to original sources
PubMed1997

Prediction of outcome of patients with life-threatening ventricular arrhythmias treated with automatic implantable cardioverter-defibrillators using SPECT perfusion imaging.

BACKGROUND: In the present study, we examined the predictors of outcome of 103 patients with coronary artery disease and left ventricular dysfunction who had life-threatening ventricular arrhythmias and were treated with implantable cardioverter-defibrillators with the use of single-photon emission computed tomography (SPECT). METHODS AND RESULTS: During a mean follow-up of 29 months, there were 29 cardiac deaths. In comparison with patients who died, survivors had less diabetes mellitus (45% versus 19%, P < .007), higher left ventricular ejection fraction (23 +/- 9% versus 27 +/- 11%, P = .04), and fewer perfusion defects as determined with stress SPECT (15 +/- 5 versus 12 +/- 5, P < .004). Most of the perfusion defects were fixed, indicative of scarring; the extent of reversible defects did not differ (2 +/- 3 in survivors and 3 +/- 4 in nonsurvivors). Multivariate Cox survival analysis identified the number of fixed defects as the only independent predictor of death (chi 2 = 10, P = .002). There were six deaths among 42 patients (14%) with < 8 fixed defects compared with 23 deaths among 61 patients (38%) with > or = 8 defects (P = .005). The 4-year survival was better in patients with < 8 segmental fixed defects than in those with > or = 8 fixed defects (80% versus 36%) (chi 2 = 8, P = .005). CONCLUSIONS: The myocardial perfusion pattern is an important determinant of outcome in patients with life-threatening ventricular arrhythmias who are treated with a implantable cardioverter-defibrillator. The extent of scarring separates patients into high- and low-risk groups with a 2.7-fold difference in death rate.

Aged↗
PubMed1996

Effects of high and low shock energies on sinus electrograms recorded via integrated and true bipolar nonthoracotomy lead systems.

INTRODUCTION: The purpose of this investigation was to prospectively evaluate the voltage- and time-dependent characteristics of a biphasic defibrillator discharge on the amplitude of the rate sensing electrogram recorded from two "integrated" and one true bipolar nonthoracotomy lead system. Prolongation of redetection time has been noted after a failed first shock with nonthoracotomy lead systems. However, a prospective evaluation of the time- and voltage-dependent effects of biphasic shocks on electrogram amplitude with clinically utilized lead systems has not been systematically performed. METHODS AND RESULTS: Five- then 30-J R wave synchronous biphasic discharges were delivered during the supraventricular rhythm through three nonthoracotomy lead systems (Medtronic Transvene, Ventritex TVL, and CPI Endotak C 60 Series). The R wave amplitude was measured immediately postshock and for up to 1 minute. Amplitude changes were compared with preshock baseline value. A 5-J discharge had minimal effect on the R wave amplitude recorded from the three lead systems; however, 30 J resulted in significant diminution in R wave amplitude recorded from the integrated bipolar leads (in the Endotak lead to a greater extent than the TVL lead) with minimal effects on the Transvene lead. Following a 30-J discharge, the time constant for R wave recovery was 4.2, 14.9, and 15.3 seconds for Transvene, TVL, and Endotak 60 leads, respectively. CONCLUSION: There are voltage- and time-dependent reductions in postshock R wave amplitude. Integrated bipolar systems appear more affected than the "true" bipolar lead evaluated. This may be due, in part, to lead design, distance of distal defibrillating surface from rate sensing cathode, and the incorporation of the defibrillating surface as the rate sensing anode. The influence of post-shock R wave diminution on subsequent redetection remains speculative but may have implications for subsequent lead development.

Adult↗
PubMed1995

Utility of the 12-lead electrocardiogram in localizing the origin of right ventricular outflow tract tachycardia.

The purpose of this investigation was to develop an algorithm on the basis of the QRS morphology observed on the 12-lead ECG that would rapidly locate the site of origin of the monomorphic ventricular tachycardia arising from the septal portion of the RVOT. Radiofrequency catheter ablation guided by pace-mapping techniques has proven effective in eliminating the ventricular tachycardia originating from the RVOT in the absence of structural heart disease. A method that would rapidly identify the portion of the RVOT septum toward which more detailed pace-mapping should be directed before catheter ablation would be useful in decreasing procedure time and radiation exposure and potentially facilitating a successful ablation procedure. The RVOT septum was divided into nine sites. In 11 patients, bipolar pacing was performed at each of the nine designated sites to mimic ventricular tachycardia. A standard 12-lead surface ECG was recorded during pacing. The QRS morphology in the limb leads was characterized and the site of the R-wave transition was determined in the precordial leads. A QS in lead a VR and a monophasic R wave in leads II, III, aVF, and V6 were noted in each patient at all paced sites. In lead I, pacing at the three posterior septal sites always resulted in an R wave. Pacing at the three anterior sites produced a dominant Q wave (either QS or Qr) at 17 (52%) of 33 sites or a qR complex at 16 (48%) of 33 sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Comparison of initial detection and redetection of ventricular fibrillation in a transvenous defibrillator system with automatic gain control.

OBJECTIVES: The purpose of this study was to prospectively evaluate postshock redetection of ventricular fibrillation by a system that coupled an implantable cardioverter-defibrillator with an automatic gain control sense amplifier and a transvenous lead system. BACKGROUND: Redetection of ventricular fibrillation after an unsuccessful first shock has not been systematically evaluated. Previous studies have suggested that sensing performance of some lead systems may be adversely affected by the delivery of subthreshold shocks. METHODS: The time required for both initial detection and redetection of ventricular fibrillation was compared in 22 patients. These times were estimated by subtracting the capacitor charge time from the total event time. RESULTS: A total of 113 successful and 57 unsuccessful initial shocks were delivered during induced ventricular fibrillation. The mean +/- SD initial time to detection of ventricular fibrillation was 5.5 +/- 1.7 s (range 2.4 to 10.8); the time to redetection ranged from 1.5 to 18.5 s (mean 4.5 +/- 2.8, p = NS vs. detection time). Abnormal redetection episodes, defined as a redetection time > 10.2 s (i.e., > 2 SD above the mean redetection time), were observed in 4 (18%) of 22 patients. CONCLUSIONS: Redetection of ventricular fibrillation after a subthreshold first shock may be delayed. Device testing with intentional delivery of subthreshold shocks to verify successful postshock redetection of ventricular fibrillation should be performed routinely in all patients.

Algorithms↗