Publications by authors named "Richard Henthorn"

3 Publications

  • Page 1 of 1

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

Pacing Clin Electrophysiol 2007 Jan;30 Suppl 1:S139-42

Rochester General Hospital, Rochester, New York, USA.

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.
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January 2007

Development of the implanted devices adjustment scale.

Dimens Crit Care Nurs 2005 Sep-Oct;24(5):242-8

University of Cincinnati-College of Nursing, Cincinnati, OH 45221-0038, USA.

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.
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December 2005

Azimilide decreases recurrent ventricular tachyarrhythmias in patients with implantable cardioverter defibrillators.

J Am Coll Cardiol 2004 Jan;43(1):39-43

University of Louisville, Division of Cardiology, Louisville, Kentucky, USA.

Objectives: This study evaluated the effects of azimilide dihydrochloride (AZ) on anti-tachycardia pacing (ATP) and shock-terminated events in patients with implantable cardioverter defibrillators (ICDs).

Background: Animal studies have shown the effectiveness of AZ for therapy of supraventricular and ventricular tachycardia (VT). Azimilide dihydrochloride was investigated as adjunctive treatment for reducing the frequency of VT and, thus, the need for ICD therapies, including ATP and cardioversion/defibrillation (ICD shocks) in patients with inducible monomorphic VT.

Methods: A total of 172 patients were randomized to daily treatment with placebo, 35 mg, 75 mg, or 125 mg of oral AZ in this dose-ranging pilot study of patients with ICDs. The majority of patients had a history of documented remote myocardial infarction and congestive heart failure New York Heart Association class II or III.

Results: The frequency of appropriate shocks and ATP were significantly decreased among AZ-treated patients compared with placebo patients. The incidence of ICD therapies per patient-year among the placebo group was 36, and it was 10, 12, and 9 among 35 mg, 75 mg, and 125 mg AZ patients, respectively (hazard ratio = 0.31, p = 0.0001). Azimilide dihydrochloride was generally well tolerated and did not affect left ventricular ejection fraction or minimal energy requirements for defibrillation or pacing.

Conclusions: Azimilide dihydrochloride may be a safe and effective drug for reducing the frequency of VT and ventricular fibrillation in patients with implanted ICDs.
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January 2004