Electrophysiological Effects of Disopyramide in Patients with Bundle Branch Block

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Abstract

SUMMARY

Electrophysiological studies were performed in 22 patients with intraventricular conductio±elay before and after intravenous infusion of disopyramide (Norpace), 2 mg/kg. Mean control maximal sinu±ode recovery time (1039 ± 187 msec), atrioventricular nodal conduction time (113 + 28 msec), and atrioventricula±odal effective refractory periods (349 ± 67 msec) did not change significantly after administratio±f disopyramide (1073 ± 284 msec, 112 ± 31 msec, and 342 ± 42 msec, respectively). Mean spontaneous cycl±ength (756 ± 146 msec) decreased significantly 5 minutes after disopyramide (717 ± 124 msec±p < 0.05), but not after 30 minutes (734 ± 142 msec). A small but statistically significant (p < 0.05) increas±ccurred after disopyramide in the mean atrial effective refractory period (259 + 51 to 280 ± 53 msec), ventricula±ffective refractory period (253 ± 23 to 275 ± 33 msec), as well as the relative refractory period of th±entricular specialized conduction system (six patients) (433 ± 78 to 479 ± 62 msec). Although mean contro±nfranodal conduction time (67 ± 35 msec) increased 5 minutes after disopyramide (79 i 41 msec±p < 0.001) (18%), no spontaneous episodes of second-degree or third-degree atrioventricular block wer±bserved. In six patients with premature ventricular depolarizations (> 1/min), the arrhythmia was totall±bolished in four, markedly reduced in one, and remained unchanged in one. Disopyramide resulted in significan±rolongation of infranodal conduction time as well as in atrial and ventricular refractoriness, bu±evertheless appears to be safe in patients with bundle branch block.

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