Relationship between plasma levels of procainamide, suppression of premature ventricular complexes and prevention of recurrent ventricular tachycardia.
We compared the relationship between plasma levels of procainamide and suppression or prevention of various forms of ventricular arrhythmias in 18 patients, six of whom had premature ventricular complexes (PVCs) during acute myocardial infarction (AMI), six of whom had PVCs in the setting of stable chronic ischemic heart disease (CIHD), and six of whom had recurrent symptomatic ventricular tachycardia (VT) with chronic PVCs between episodes of VT. The mean plasma level of procainamide required for 85% suppression of PVCs in the AMI patients was 5.0 +/- 0.5 micrograms/ml, while that required for the CIHD patients was 9.3 +/- 0.7 micrograms/ml (p less than 0.05). The mean plasma level required for prevention of spontaneous episodes of symptomatic sustained tachycardia in the VT group was 9.1 +/- 3.4 micrograms/ml, while the mean level required for 85% suppression of PVCs in the same patients was 14.9 +/- 3.8 micrograms/ml (p less than 0.01). In the VT group, PVC frequency was decreased by a mean of only 36% (range 11-63%) at plasma levels of procainamide sufficient to prevent spontaneous VT. The relationship between plasma levels of procainamide and PVC suppression appears to be different in AMI and CIHD patients; furthermore, a high degree of PVC suppression is not a necessary endpoint of antiarrhythmic therapy when attempting to protect patients against recurrent symptomatic VT.