Electrophysiological and electropharmacological studies in pre-excitation syndromes: results with propafenone therapy and isoproterenol infusion testing.

To study the electrophysiological effects of oral propafenone on accessory pathways and determine the potential for catecholamine-mediated reversal of these effects, comprehensive electrophysiology studies (EPS) were conducted in 11 patients with manifest (n = 9) or concealed (n = 2) pre-excitation syndrome. EPS were performed at baseline (in the drug-free state), after oral propafenone loading, and with isoproterenol infusion during propafenone therapy. The study group included 10 men and 1 woman with a mean age of 39 +/- 13 years, who presented with symptoms of palpitations (n = 6), presyncope (n = 3) and syncope (n = 2). The clinical arrhythmia was atrioventricular reciprocating tachycardia (n = 6), atrial flutter/fibrillation (n = 3), or both (n = 2). During the baseline EPS the accessory pathway location was identified as left (n = 6) or septal (n = 5). The mean anterograde effective refractory period was 265 +/- 42 ms, the shortest pre-excited RR interval 259 +/- 20 ms and the retrograde refractory period 258 +/- 39 ms. Orthodromic atrioventricular reciprocating tachycardia was induced in 10 patients (mean cycle length = 324 +/- 31 ms). Antidromic reciprocating tachycardia was induced in one patient (cycle length = 340 ms). In all the 11 patients EPS were repeated after 4 days of oral propafenone loading (668 +/- 226 mg daily) when drug steady state was expected to have been achieved. One additional patient had baseline EPS but developed clinical arrhythmia recurrences after propafenone loading and thus he was excluded from the study; follow-up EPS were conducted on procainamide.(ABSTRACT TRUNCATED AT 250 WORDS)