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Notes: Recent interest in curriculum integration in the decision sciences has led to the proposal that topics in computer science, statistics, quantitative methods, operations research, and possibly mathematics might be integrated into a single unified set of courses. Such a unification may reinforce the learning process of the student and form the basis for the eventual synthesis of tools topics with functional area decision making. This integration proposal and speculation is examined using research in learning and motivation theory, and concludes that the integration of tools concepts with functional area topics is much more promising than the integration of tools topics alone. A pair of example course integrations is provided to illustrate in detail the application of learning and motivation principles to tools-into-functions curriculum integration.

Notes: Biphasic Transvenous Defibrillation. Introduction: Biphasic waveform defibrillation is not always more efficacious than monophasic waveform defibrillation. Methods and Results: Waveform efficacy appears to vary with the lead system used. In this prospective, randomized study, defibrillation efficacy with biphasic and monophasic single capacitor 120μF, 65% tilt pulses was compared for a lead system consisting of right ventricular (RV), chest patch (CP), and superior vena cava (SVC) electrodes. Although this lead system is commonly used with monophasic pulses in transvenous defibrillators, few studies have examined the defibrillation efficacy of this lead system in man for biphasic waveform defibrillation. Fourteen cardiac arrest survivors undergoing defibrillator implantation were included in the study using pulses delivered from a cathodal RV electrode simultaneously to anodal SVC and CP electrodes. Biphasic and monophasic waveforms were recorded oscilloscopically to acquire defibrillation threshold (DFT) data on leading edge voltage requirements and for stored energy. The monophasic DFT voltage was 661 ± 177 V compared to the biphasic DFT voltage of 451± 185 V (P 〈 0.0001). The monophasic DFT stored energy was 28.0 ± 13.4 J compared to the biphasic DFT stored energy of 14.1 ± 12.4 J (P ± 0.0001). The stored energy DFT was 〈 15 J in only 2 of 14 patients (15%) with monophasic defibrillation but 〈 15 J in 10 of 14 (71%) patients with biphasic defibrillation. Conclusion: These findings indicate that biphasic defibrillation with an RV, SVC, CP transvenous electrode system is substantially more efficient than monophasic defibrillation. allowing for higher numbers of patients to receive transvenous defibrillators with a relatively simple lead system at a satisfactory cutoff DFT safety margin of 15 J.

Notes: Atrial Fibrillation After Ventricular Defibrillation. Introduction: The induction of atrial fibrillation (AF) following implantable defibrillator therapy of ventricular fibrillation carries multiple risks. The frequency of shock-induced AF may be more problematic in patients with transvenous defibrillators because current is often delivered through atrial tissue. Thus, the purpose of this study was to determine the incidence of AF following transvenous ventricular defibrillation. Methods and Results: Atrial electrograms were recorded before and after energy delivery in patients undergoing intraoperative testing of transvenous defibrillation lead systems. A total of 114 tracings were examined from 21 patients following ventricular defibrillation. Transvenous deflbrillation shock strength ranged between 200–800 volts (2–40 joules). Bipolar atrial electrograms were obtained from atrial electrodes with 1-cm interelectrode spacing located on one of the defibrillation catheters. The timing of the ventricular defibrillation shock was expressed as a percentage of the preceding sinus PP interval. Three of the 114 transvenous shocks (2.6%) generated AF. Each episode of AF occurred in a different patient. The shocks responsible for AF occurred at 21%, 43%, and 84% of the preceding sinus PP interval. No relation was found between AF induction and the timing of pulse delivery, pulse strength, or pulse number. Conclusion: We conclude that transvenous ventricular defibrillation infrequently causes AF and that timing shock delivery to the atrial cycle is likely to be of marginal or no benefit in the prevention of shock-induced AF. (J Cardiovasc Electrophysiol, Vol. 3, pp. 411–417, October 1992)

Notes: Damped Sine Wave Defibrillation Pulses. Introduction: Damped sine wave pulses have been used for nearly 50 years in transthoracic defibrillation systems. The purpose of this study was to determine whether damped sine wave pulses have a role in implantable defibrillators. Methods and Results: In 21 survivors of cardiac arrest, we prospectively compared defibrillation efficacy of a standard truncated capacitor (RC) monophasic pulse with a damped sine wave inductor-capacitor (LRC) pulse using a right ventricular-left ventricular epicardial patch-patch electrode system. The RC pulse was a standard 65% tilt monophasic waveform generated from a 120μF capacitor. The LRC pulse was designed to simulate the waveform currently used in transthoracic defibrillators and was generated by passing the charge stored on a 40μF capacitor through a 37-mH inductor. Capacitor voltage, peak delivered voltage, peak delivered current, discharge pathway resistance, delivered energy, and stored energy were compared for the two waveforms at the defibrillation threshold. There was no difference in defibrillation efficacy for the two waveforms. Peak delivered voltage was similar at the defibrillation threshold: 313 ± 101 V for the RC pulse and 342 ± 119 V for the LRC pulse (P = 0.16). Similarly, no differences were found in defibrillation threshold peak delivered current: 8.6 ± 2.5 (RC) versus 9.3 ± 2.7 (LRC) amperes (A) (P = 0.20); discharge pathway resistance: 37 ± 11 (RC) versus 38 ± 13 (LRC) O (P = 0.71); delivered energy: 7.0 ± 4.5 (RC) versus 7.0 ± 4.0 (LRC) joules (J) (P = 0.88); and stored energy: 8.7 ± 5.7 (RC) versus 9.8 ± 5.4 (LRC) J (P = 0.35). Although both waveforms performed the same, it was necessary to use substantially higher stored voltages with the damped sine wave delivery system than with the truncated waveform delivery system: 356 ± 110 V for the RC pulse and 675 ± 192 V for the LRC pulse (P 〈 0.0001). Conclusion: This study demonstrates that RC monophasic pulses provide equally effective epicardial defibrillation as LRC pulses with respect to delivered voltage and current and stored and delivered energy. However, in order for LRC pulses to provide comparable delivered voltage, current, and energy to that of RC pulses, nearly twice the voltage must be stored on the capacitor to accomplish the same task. These findings suggest that despite the nearly 50-year experience with damped sine wave pulses with transthoracic defibrilliitors, there is no need to begin using damped sine wave pulses for implantabte defibrillators. Moreover, these data raise a question regarding the need for inductors in transthoracic defibrillators.

Notes: A SYMPOSIUM