Analysis of the defibrillation efficacy for 5-ms waveforms.

Introduction: Empirical studies have shown that biphasic defibrillation waveforms are more efficacious than monophasic waveforms. However, a more systematic approach to waveform development might be more productive. This study tested 147 multiphasic waveforms uniformly sampled from all possible 5-ms waveforms.

A novel ultrasound technique to estimate right ventricular geometry during fibrillation.

Finite element modelling of the heart for the purpose of studying the electric fields of defibrillation shocks requires knowledge of the geometry of the heart during fibrillation. However, the standard method of measuring this geometry, MRI. cannot be used during fibrillation because the heart geometry changes rapidly and perhaps unpredictably.

Large sample test of defibrillation waveform sensitivity.

Introduction: An unknown mechanism causes defibrillation efficacy to be sensitive to the temporal pattern (waveform) of the delivered energy. Using a guinea pig model, we tested hypotheses in 140 defibrillation waveforms.

Methods And Results: Two hundred seven male guinea pigs (950 +/- 100 g) were instrumented to continuously monitor the ECG and an optical plethysmographic signal from a forepaw.

Mechanisms by which AC leakage currents cause complete hemodynamic collapse without inducing fibrillation.

Introduction: The first study of weak alternating current (AC) stimulation in closed chest humans showed that complete hemodynamic collapse can occur below the threshold for inducing ventricular fibrillation (VF), a heretofore unknown danger to patients. This article, and the accompanying simulation article, explore the mechanisms responsible for the collapse.

Methods And Results: A quadripolar pacing catheter was placed in the right ventricle (RV) of six dogs.

A four-shock Bayesian up-down estimator of the 80% effective defibrillation dose.

Introduction: New defibrillation techniques are often compared to standard approaches using the defibrillation threshold. However, inference from thresholding data necessitates extrapolation from reactions to relatively ineffective shocks, an error prone procedure requiring large sample sizes for hypothesis testing and large safety margins for defibrillator implantation. In contrast, this article presents a clinically validated statistical model of a minimum error, four-shock defibrillation testing protocol for estimating the 80% effective defibrillation strength for a given patient (ED80).