PMID: 8608459Apr 1, 1996Paper

Order in disorder: effect of barium on ventricular fibrillation

The Canadian Journal of Cardiology
Paul DorianF X Witkowski

Abstract

Drugs that prolong cardiac refractoriness can decrease defibrillation energy requirements. In particular, barium, a relatively selective blocker of cardiac Ik1 channels, produces marked decreases in defibrillation energy. The mechanism of this effect is unknown, and may relate to modulation of the effect of defibrillatory shocks, or an alteration of the pattern of ventricular fibrillation (VF) by the drug. Accordingly, the effect of barium chloride was examined, 1.1 mg/kg followed by 0.1 mg/kg/min intravenously, or saline control, on the pattern of unipolar electrograms using a 120 electrode array, during 73 episodes of VF (37 after saline, 36 after barium ). For each episode of VF, peak-dV/dt associated with local activations and mean activation-activation (ACT-ACT) intervals for the last 2 s of a 10 s episode of VF were measured for each electrode. 'Organization' in VF was measured by the variability in ACT-ACT intervals, their visually assessed pattern, and the relation between local activations on adjacent electrodes. Voltage gradients were measured at each of 40 epicardial sites for each defibrillation shock, delivered at voltages ranging from to 20% to 100% successful in defibrillation. At identical voltage shocks (400 V)...Continue Reading

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