Electrophysiologic Effects of Procaine Amide in Patients with Intraventricular Conduction Delay

In 16 patients with intraventricular conduction delay (IVCD) and cardiac arrhythmias, procaine amide (PA) was infused intravenously at rates of 30-40 mg/min until a maximum dose of 750-1,000 mg was administered. His bundle electrograms and plasma PA levels were obtained every 5 min during infusion and for 25 min thereafter. The mean peak PA level (10.2 ± 3.4 µg/ml) was achieved at the end of infusion. Mean control A-V nodal conduction times (A-H: 99.5 ± 34 msec) and A-H at peak PA levels (90 ± 15.3) did not differ significantly. However, the mean infranodal conduction time (H-Q) at peak PA (68.1 ± 14.8 msec) was significantly higher than control measurements (57.6 ± 13 msec) ( P < 0.001), with a mean percent increase of 18% (11 msec), and maximal prolongation of H-Q occurred at peak PA blood levels. There was no statistically significant correlation between maximum absolute or percent change in H-Q and control H-Q, control QRS duration, or peak PA levels. One patient with sinus bradycardia had further decreases in rate and a junctional rhythm after PA. Intravenous administration of PA appears safe and effective for patients with IVCD in terms of arrhythmia control and absence of high degree A-V block, ventricular ectopic beats, or standstill, but caution should be used in treating patients with sinus bradycardia.