"Tuned" defibrillation waveforms outperform 50/50% tilt defibrillation waveforms: a randomized multi-center study.

INTRODUCTION: A superior performance of a tuned waveform based on duration using an assumed cardiac membrane time constant of 3.5 ms and of a 50/50% tilt waveform over a standard 65/65% tilt waveform has been documented before. However, there has been no direct comparison of the tuned versus the 50/50% tilt waveforms. METHODS: In 34 patients, defibrillation thresholds (DFTs) for tuned versus 50/50% tilt waveforms in a random order were measured by using the optimized binary search method. High voltage lead impedance was measured and used to select the pulse widths for tuned and 50/50% tilt defibrillation waveforms. RESULTS: Delivered energy (7.3 +/- 4.6 J vs 8.7 +/- 5.3 J, P = 0.01), stored energy (8.2 +/- 5.1 J vs 9.7 +/- 5.6 J, P = 0.01), and delivered voltage (405.9 +/- 121.7 V vs 445.0 +/- 122.6 V, P = 0.008) were significantly lower for the tuned than for the 50/50% tilt waveform. In four patients with DFT >/= 15 J, the tuned waveform lowered the mean energy DFT by 2.8 J and mean voltage DFT by 45 V. For all patients, the mean peak delivered energy DFT was reduced from 29 J to 22 J (24% decrease). Multiple regression analysis showed that a left ventricular ejection fraction < 20% is a significant predictor of this advantage. CONCLUSION: Energy and voltage DFTs are lowered with an implantable cardioverter defibrillator that uses a tuned waveform compared to a standard 50% tilt biphasic waveform.

Development of the implanted devices adjustment scale.

Advances in microelectronics have resulted in exponential growth in the number of implanted medical devices. Most people do well adjusting to their devices, but others show signs of depression and/or anxiety. The Implanted Device Adjustment Scale (IDAS) was developed to measure how well a person is adjusting to an implanted device. First, a pool of items was generated and reviewed by 2 panels of clinicians and psychometricians for content validity. The revised version was then administered to a small sample that provided information about problematic items. Finally, a convenience sample of 45 persons (66% males) with implanted devices (18 pacemakers only, 37 cardioverter/defibrillators) completed the revised IDAS twice. After deleting weak items, the Cronbach alpha was 0.90. No age, gender, or device differences were found. Test-retest reliability was 0.92. The IDAS may be useful to evaluate how well a person is adjusting to her/his device. This may lead to more timely and appropriate interventions to improve outcomes.