using 10 isolated , blood-perfused canine atrial , and ventricular preparations , the effects of d- and l-verapamil on sa nodal pacemaker activity and contractility were investigated . l-verapamil and d-verapamil produced dose-related negative chronotropic and inotropic effects in all experiments . l-verapamil was approximately 10 time more potent than d-verapamil both in inotropism and chronotropism .
C1372752
negative chronotropic
C0042523
verapamil