A 45-year-old man is noted to have dilated cardiomyopathy with atrial fibrillation and a rapid ventricular rate. An agent is used to control the ventricular rate, but the cardiac contractility is also affected, wof agents was most likely used

Verapamil Of the many Ca2+ channel blockers, verapamil has the most prominent cardiac electrophysiological action. It blocks L type Ca2+ channels and delays their recovery. mech of action:- The basic action of verapamil is to depress Ca2+ mediated depolarization. This suppresses automaticity and reentry dependent on slow channel response. Phase-4 depolarization in SA node is reduced resulting in bradycardia. The most consistent action of verapamil is prolongation of A-V nodal ERP. As a result A-V conduction is markedly slowed (P-R interval increases) and reentry involving A-V node is terminated. Verapamil has negative inotropic action due to interference with Ca2+ mediated excitation-contraction coupling in myocardium. Ref:- kd tripathi; pg num:-535