Intropic effects of several antiarrhythmic drugs.

The effects of intravenous administration of several quinidine-like antiarrhythmic drugs (bunaftine, monochloroacetyl ajmaline, lidocaine, mexiletine, disopyramide, aprindine, diphenylhydantoin, procainamide) on left ventricular performance, evaluated by systolic time intervals (STI), were studied in 100 patients with atherosclerotic heart disease. The STI were measured: the pre-ejection period (PEP), the isometric contraction time (ICT), the left ventricular ejection time (LVET), corrected LVET (LVETc), and the PEP/LVET ratio. The degree of impairment of left ventricular performance was maximal after aprindine and disopyramide administration. This was demonstrated by significant increases in the PEP, ICT, and PEP/LVET and by significant decreases in LVET and LVETc, in patients in both III-IV and I-II NYHA classes. Bunaftine, monochloroacetyl ajmaline, and lidocaine induced a less marked impairment of myocardial performance, since the PEP, ICT, and PEP/LVET increases were not significant compared to controls in patients in NYHA class I-II, and since no variation of LVET and LVETc were observed. Mexiletine effects on myocardial performance appear to be intermediate between these groups of drugs. Diphenylhydantoin and procainamide, considered separately because of their effects on heart rate and blood pressure which are not possessed by the other drugs, induced significant increases of PEP in NYHA class III-IV patients. However, the effects of these 2 drugs on myocardial performance may have been underestimated, due to the concomitant hemodynamic effect of these drugs.