Hemodynamic and electrophysiologic effects of encainide in patients with bundle branch block
Schwartz, A.B.; Shapiro, W.A.; Suave, M.J.; Shen, E.; Bhandari, A.; Morady, F.; Scheinman, M.
Canadian Journal of Cardiology 3(2): 75-82
1987
ISSN/ISBN: 0828-282X PMID: 3105850 Document Number: 304614
Electrophysiologic studies were performed in 6 consecutive patients with bundle branch block and organic heart disease. All were studied after intravenous (0.9 mg/kg) encainide and 3 of the 6 after 36-72 hours of oral encainide (50 mg every 6 hours). After intravenous encainide, mean H-Q increased from 51 .+-. 20 msec to 58 .+-. 25 msec (14% p .ltoreq. .05). After oral encainide (3 patients) H-Q increased to 90 .+-. 39 msec (56% p .ltoreq. .05, compared to baseline). Programmed ventricular stimulation was performed in 5. In 1 patient without spontaneous ventricular tachycardia, tachycardia was non-inducible before and after encainide. Of 5 patients with spontaneous arrhythmia, 3 had ventricular tachycardia induced before and after intravenous encainide at mean cycle lengths of 287 .+-. 130 msec and 407 .+-. 261 msec, (not significant) respectively, while 1 had ventricular tachycardia induced only after encainide. Four patients began chronic treatment with oral encainide (2 patients with inducible rapid ventricular tachycardia after encainide were excluded). All suffered major adverse outcomes. One died suddenly after an electrophysiology study demonstrated inducible ventricular tachycardia, which occurred only after encainide. One experienced new syncope after baseline H-Q increased 75% after encainide. Two patients developed new sustained atrial tachycardias and 1 patient developed persistent ventricular tachycardia on encainide. In patients with bundle branch block, encainide was (1) associated with marked prolongation of H-Q especially after oral administration; (2) proved ineffective in suppressing inducible ventricular tachycardia; (3) had a significant proarrhythmic effect. Although a small number of patients were studied, the frequency of adverse effects with encainide suggests that it should be used with caution in patients with cardiac disease and bundle branch block.