[Comparative studies on the contractile and hemodynamic effects of antiarrhythmic agents (lidocaine, diphenylhydantoin, ajmaline) (author's transl)].

The contractile and hemodynamic effects of lidocaine, diphenylhydantoin and ajmaline were compared in isolated ventricular myocardium and in patients during diagnostic cardiac catheterization. The animal experiments show that diphenylhdantoin is 3-5 times more potent as a contractility inhibitor than lidocaine. This experimental relationship correlates with the clinical findings in which only small decreases in the pumping function of the left ventricle appear with lidocaine while diphenylhydantoin has a 2-2.5 times stronger depressor effect (reduction of cardiac output, cardiac index, stroke volume by 17-20%). With ajmaline there is a decrease of the stroke volume by a maximum of 17% and changes in isovolumetric contractility quantities corresponding to a decrease in myocardial contractility of 16-22%. It may be concluded from these findings that diphenylhydantoin and ajmaline may be accompanied by marked decreases in hemodynamic and contractile quantities of the left ventricle. The relative power of lidocaine to inhibit contractility is small, so that even in the presence of an existing disturbance of myocardial function, only a slight additional decrease in pumping function is to be expected.