Verapamil for refractory ventricular fibrillation during cardiac operations in patients with cardiac hypertrophy.

Calcium-entry blockers prevent ventricular fibrillation during acute myocardial ischemia in laboratory animals. They may be useful as an adjunct to cold cardioplegia by preserving the myocardium during cardiopulmonary bypass. Their use may limit myocardial infarct size. However, the clinical application of calcium-entry blockers for ventricular dysrhythmias associated with myocardial ischemia has been little explored, as yet. We describe four patients, all of whom had significant cardiac hypertrophy (two had idiopathic hypertrophic subaortic stenosis; one had transposition of great vessels; and one had aortic stenosis) and in whom ventricular fibrillation developed after rewarming or shortly after the termination of bypass. The dysrhythmias were refractory to multiple attempts at defibrillation and conventional pharmacologic interventions. However, in each case, defibrillation was successful after administration of verapamil.