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Comparative effects of verapamil and nifedipine on reactive hyperemia and ventricular arrhythmias during coronary artery reperfusion

1980; Oxford University Press; Volume: 1; Issue: suppl 2 Linguagem: Inglês

10.1093/eurheartj/1.suppl_2.31

1522-9645

Lair G.T. Ribeiro, Thomas L. DeBauche, T.L. Brandon, Peter R. Maroko, Richard R. Miller,

Cardiac Arrhythmias and Treatments

The goal of this investigation was to examine effects of the calcium antagonists verapamil and nifedipine on coronary hemodynamics and ventricular arrhythmias during coronary reperfusion. Accordingly, 24 dogs were anesthetized, and their hearts exposed through a left lateral thoracotomy. The left anterior coronary artery was occluded at its midportion and 25 min later the occlusion was released. Regional myocardial blood flow (RMBF) was determined using the microsphere technique ( 85 Sr and 141 Ce, 8–10 μ in diameter). It was determined 20 min after occlusion and 10 min after reperfusion. Twenty minutes after occlusion, immediately after microsphere injection, dogs were randomized into eight control dogs, eight verapamil dogs (0.2 mg/kg in 5 min followed by 0.01 mg/kg/min infusion) and eight nifedipine dogs (0.1 mg/kg in 5 min followed by 0.003 mg/kg/min infusion). In the control dogs, six out of eight animals had either ventricular tachycardia (three dogs) or ventricular fibrillation (three dogs). In the verapamil group, none had ventriclar tachycardia and only one had ventricular fibrilation (P<0.05 v. C). In the nifedipine group four out of eight had either ventricular tachycardia (two dogs) or fibrillation (two dogs) (P = NS v. C). Ten minutes after reperfusion, coronary resistance in ischemic myocardium declined similarly in all three groups (by 80–90%). Thus, verapamil decreases reperfusion ventricular arrhythmias without altering RMBF. Although both verapamil and nifedipine are calcium antagonists, their antiarrhythmic effects differ in reperfusion-induced arrhythmias.