Effect of procainamide on left ventricular performance in patients with primary myocardial disease

The effect of procainamide (P) on left ventricular function as measured by the systolic time intervals (STI) was studied in 14 patients with primary myocardial disease. P, 7.5 mg/kg body weight, was given intravenously at a rate of 100 mg per minute. Administration of P produced a decrease in left ventricular performance as manifest by a significant prolongation of the pre-ejection period corrected for heart rate (PEPI) and an increase of the PEP to the left ventricular ejection time (LVET) ratio. The peak effect on PEPI and PEP/LVET occurred at 2 minutes after P administration (delta PEPI + 14 +/- 1.9 ms, p < 0.001, delta PEP/LVET + 0.052 +/- 0.007, p < 0.001) with values returning towards baseline by 60 min. In 6 of the patients P blood levels were measured simultaneously with the STI measurements. Changes in PEPI and PEP/LVET directly parallel changes of P blood levels. It is concluded that P given intravenously at the usual therapeutic doses decreases left ventricular performance in patients with primary myocardial disease. These changes in left ventricular performance directly parallel procainamide blood levels.