Evolving concepts of management of stable and potentially lethal arrhythmias

Recent studies indicate that the eradication of premature ventricular complexes (PVCs) by antiarrhythmic agents is an inadequate end point for estimating long-term protection against potentially lethal arrhythmias. In a study of survivors of prehospital ventricular fibrillation (VF), who have a 30% risk for recurrent VF during the first year of follow-up, we observed an apparent protection against recurrent VF by antiarrhythmic agents even if chronic PVCs were not suppressed by stable therapeutic plasma levels. To expand the data base pertinent to the relationships between PVCs and advanced arrhythmias, we studied six patients with chronic recurrent ventricular tachycardia (VT) and frequent PVCs between episodes of VT. Plasma levels of procainamide (PA) required to protect against recurrent VT averaged 9.4 +/- 3.4 microgram ml, compared with mean levels of 14.9 +/- 3.8 microgram/ml for 85% suppression of PVCs (p less than 0.01). PVC frequency decreased by a mean of only 36% (range -11% to -63%) at plasma levels of PA sufficient to prevent spontaneous VT. Concentration-response relationships between (PA) and PVC suppression were also compared in patients with PVCs during acute myocardial infarction and in patients with PVCs in stable chronic ischemic heart disease. In the former group of patients the mean plasma level of PA required to suppress 85% of the PVCs was 5.0 +/- 0.5 microgram/ml, and in the latter group was 9.3 +/- 0.7 microgram/ml (p less than 0.001). We conclude that the relationship between plasma levels of PA and PVC suppression is different in the two groups of patients, and furthermore, that a high degree of PVC suppression may not be a necessary end point for protecting patients against symptomatic recurrent VT or VF.