Usefulness of the response to intravenous procainamide during electrophysiologic study in predicting the response to oral quinidine in patients with inducible sustained monomorphic ventricular tachycardia associated with coronary artery disease.

The response to intravenous procainamide (15 to 20 mg/kg) and to oral quinidine 324 to 648 mg every 8 hours for 3 to 5 days was prospectively studied in 50 consecutive patients (43 men and 7 women, aged 38 to 83 years old [mean 64 +/- 11]) with coronary artery disease and baseline-inducible sustained monomorphic VT. Mean procainamide and trough quinidine serum levels were 10.5 +/- 2.6 and 2.6 +/- 0.8 micrograms/ml, respectively. Mean left ventricular ejection fraction was 37 +/- 12%. Sustained monomorphic VT was suppressed by intravenous procainamide in 18 patients (36%); 8 of these patients (44%) also had suppression with oral quinidine, but 10 (56%) did not. Of the 32 patients (64%) who continued to have inducibility with intravenous procainamide, 12 (38%) responded to oral quinidine and 22 (62%) did not. The overall concordant response rate to intravenous procainamide and oral quinidine was 56% (28 of 50 patients). It is concluded that the response (i.e., the presence or absence of inducible sustained monomorphic VT) to intravenous procainamide does not adequately predict the response to oral quinidine in patients with coronary artery disease and sustained monomorphic VT.