LV mass and defibrillation threshold

“…A second major finding of this study was the demonstration of a good linear correlation between the ApEn and the DFT. Previous studies have shown that tissue mass either correlated weakly with DFT (5) or had no correlation with DFT (7). In none of these studies, however, was entropy measured.…”

Section: Apen and Dftmentioning

confidence: 86%

The Role of Approximate Entropy in Predicting Ventricular Defibrillation Threshold

Hamzei

Ohara

Kim

et al. 2002

J Cardiovasc Pharmacol Ther

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Why Do Some Patients Have High Defibrillation Thresholds at Defibrillator Implantation?

Hillsley

Wharton

Cates

et al. 1994

Pacing Clinical Electrophis

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Implantable cardioverter defibrillators reduce the risk of sudden cardiac death in patients with ventricular tachyarrhythmias. However, for the few patients with unacceptably high defibrillation thresholds at implantation the risk of sudden death may remain high. If a small number of defibrillation attempts are used to determine a defibrillation threshold, then a high defibrillation threshold may occur in some patients due to the probabilistic nature of defibrillation: a small percentage of shocks will fail even at optimal shock strengths. Basic investigations have suggested mechanisms for high defibrillation thresholds in other patients. The extracellular potential gradients produced by a shock correlate with ability to defibrillate and may be used to classify mechanisms for high defibrillation thresholds. Computerized mapping studies have demonstrated that extracellular potential gradient fields produced by defibrillation shocks are uneven with high gradient areas close to the electrodes and low gradient areas distant from the electrodes. A high defibrillation threshold may occur because: (1) a shock creates a subthreshold potential gradient in the low gradient areas; (2) a patient has a higher minimum potential gradient threshold than other patients; or (3) a shock leads to refibrillation in the high gradient areas. This article reviews experimental evidence to support each of these three possibilities then suggests experimental and clinical investigations that may clarify the causes of high defibrillation thresholds in patients.

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Stability of the Defibrillation Probability Curve with the Development of Ventricular Dysfunction in the Canine Rapid Paced Model

Friedman

Foley

Christian

et al. 1998

Pacing Clinical Electrophis

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Most patients with implantable defibrillators have diminished cardiac function. Progressive heart failure might impair defibrillation efficacy, leading to interpreted device failure. This study sought to determine the effect of ventricular dysfunction on defibrillation energy using a biphasic endocardial system. Eleven dogs were ventricularly paced at 225 pulses/min for 2 weeks to induce ventricular dysfunction, and five control dogs remained unpaced. Dose response defibrillation probability curves were generated for each animal at baseline, after 2 weeks (at which time the pacemakers were turned off in the paced group), and then 1 week later. The defibrillation thresholds, ED20, ED50, and ED80 (the 20%, 50%, and 80% effective defibrillation energies, respectively) were determined for each dog at each study. In the paced dogs, the mean ejection fraction fell from 55% to 25% after pacing (P < 0.0001), and rose to 46% after its discontinuation (P = 0.0002). The defibrillation threshold, ED20, ED50, and ED80 remained unchanged in both the control and paced groups for all three studies, even after adjustment for dog weight or left ventricular mass. Rapid pacing produced no change in left ventricular mass. It induced ventricular cavity dilatation and wall thinning, which had opposing effects on defibrillation energy requirements, resulting in no net change of the ED50 in heart failure. In conclusion, the defibrillation efficacy of a biphasic transvenous system is not changed by the development of heart failure using the rapid paced canine model.

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LV mass and defibrillation threshold

Cited by 4 publications

References 3 publications

The Role of Approximate Entropy in Predicting Ventricular Defibrillation Threshold

The Role of Approximate Entropy in Predicting Ventricular Defibrillation Threshold

Why Do Some Patients Have High Defibrillation Thresholds at Defibrillator Implantation?

Stability of the Defibrillation Probability Curve with the Development of Ventricular Dysfunction in the Canine Rapid Paced Model

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