Thirty-eight patients who had inducible sustained
ventricular tachycardia during baseline programmed electrical stimulation underwent electrophysiologic testing after both intravenous and
oral administration of
procainamide. Each had presented clinically with documented sustained
ventricular tachycardia or
out of hospital cardiac arrest not associated with acute
myocardial infarction. In 23 patients (61%) (Group I) the
arrhythmia became noninducible during an
intravenous infusion of
procainamide. Oral
procainamide was subsequently administered and retesting was carried out after dose titration to match plasma concentration at the end of the intravenous study. Among the 23 patients in Group I the mean (+/- SD) plasma
procainamide level was 7.2 +/- 2.8 micrograms/ml after intravenous dosing and 7.9 +/- 2.5 micrograms/ml after oral dosing (p = 0.09). In 15 (65%) of the 23 patients, sustained ventricular
arrhythmia was inducible on oral
therapy with comparable plasma
procainamide levels (intravenous = 6.3 +/- 2.1 micrograms/ml, oral = 7.5 +/- 2.1 micrograms/ml). The other eight patients (35%) had concordant responses to repeat testing with comparable intravenous (mean 9.0 +/- 3.3 micrograms/ml) and oral (8.8 +/- 3.1 micrograms/ml) plasma
procainamide levels. In the additional 15 patients (Group II) sustained
ventricular tachyarrhythmia remained inducible on intravenous
procainamide therapy and the patients were retested on oral
therapy with similar plasma concentration (p = 0.05). In seven patients (47%) sustained
ventricular tachyarrhythmia was noninducible on treatment with oral
procainamide (mean plasma level 7.6 +/- 2.7 micrograms/ml) after failure of intravenous
procainamide (mean plasma level 10.3 +/- 2.3 micrograms/ml).(ABSTRACT TRUNCATED AT 250 WORDS)