The effect of procainamide on T wave alternans

Procainamide and T-Wave Alternans. Introduction: The measurement of microvo lt level T wave alternans (TWA) is a technique for detecting arrhythmia vul nerability. Previous studies demonstrated that the magnitude of TWA is depe ndent on heart rate. However, the effects of antiarrhythmic drugs on TWA ar e unknown. Methods and Results: This was a prospective evaluation of intravenous proca inamide on TWA in 24 subjects with inducible sustained ventricular tachycar dia (VT). Measurements of TWA were performed at baseline in the drug-free s tate and after procainamide loading (1,204 +/- 278 mg). Recordings were mad e in normal sinus rhythm, and during atrial pacing at 100 beats/min and 120 beats/min. The magnitude of TWA in the vector magnitude lead was decreased by procainamide at all heart rates: 0.6 +/- 0.8 to 0.3 +/- 0.4 mu V in sin us rhythm, 2.0 +/- 1.6 to 0.7 +/- 0.7 mu V at 100 beats/min, and 3.0 +/- 2. 0 to 1.7 +/- 1.8 uV at 120 beats/min (P < 0.001 by analysis of variance). T he sensitivity of TWA for the induction of VT at baseline was 5% in sinus, 60% at 100 beats/min, and 87% at 120 beats/min, while it decreased with pro cainamide to 5%, 19%, and 60%, respectively. Decreases in TWA in response t o procainamide were independent of the antiarrhythmic effects on VT inducib ility. Conclusions: These results indicate that the magnitude of TWA decreases wit h acute procainamide loading and this effect decreases the sensitivity of T WA for the induction of sustained VT. (J Cardiovase Electrophysiol, Vol. 10 , pp. 649-654, May 1999).