Electrophysiologic Effects of Procaine Amide in Patients with Intraventricular Conduction Delay

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Abstract
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.