Verapamil reduced ventricular fibrillation incidence from 80% to 20% in isolated rat hearts (P<0.05), an effect that was attenuated to 40% by doubling the extracellular calcium concentration.
Absolute Event Rate: 20% vs 80%
p-value: p=<0.05
An isolated heart method that has been proposed to aid in ascertaining the involvement of L-type calcium channel blockade in the mechanism of action of novel antiarrhythmic drugs involves increasing the calcium concentration in the perfusion buffer. The purpose of this study was to determine the validity of this method using an established L-type calcium channel blocker, verapamil. Isolated rat hearts were perfused with normal calcium (1.4 mM) Krebs solution containing drug vehicle only, a normal calcium solution containing verapamil (300 nM), or a high calcium (2.8 mM) solution containing verapamil. The occurrence of ventricular fibrillation during a subsequent period of regional myocardial ischemia was monitored. The incidence of ventricular fibrillation was significantly reduced from 80% in controls to 20% by perfusion with verapamil in normal calcium Krebs solution (P 0.05 versus controls). We conclude that the antiarrhythmic effect of verapamil in isolated hearts can be attenuated by increasing the calcium content of the perfusion solution, but a twofold increase in the calcium concentration failed to fully restore susceptibility to ventricular fibrillation to that observed in verapamil-free controls.
Lieu et al. (Tue,) conducted a other in Ventricular fibrillation during myocardial ischemia. Verapamil in normal or high calcium solution vs. Drug vehicle only in normal calcium (1.4 mM) solution was evaluated on Incidence of ventricular fibrillation (p=<0.05). Verapamil reduced ventricular fibrillation incidence from 80% to 20% in isolated rat hearts (P<0.05), an effect that was attenuated to 40% by doubling the extracellular calcium concentration.