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Ventricular tachycardia has become a relatively common complication of myocardial infarction and often is an important therapeutic problem, as it is recurrent and life-threatening. Here we report a group of 36 patients with ventricular tachycardia occurring 13 days to 30 years after a myocardial infarction. All patients were resistant to medical treatment and 34 of the 36 patients had had at least one cardiac arrest. All were candidates for surgery for their arrhythmia. The study protocol included prolonged ECG monitoring, a preoperative electrophysiological study with catheter mapping and intraoperative epicardial and endocardial mapping. A total of 52 different tachycardias were mapped in 36 patients. The procedure was facilitated by an automatic mapping device, that allowed the acquisition of 35 simultaneous signals, so that even pleomorphic ventricular tachycardias could be mapped. The information obtained from both preoperative and intraoperative maps guided surgery and restricted the extent of the surgical damage.

The electrophysiologic effects of encainide were studied in 10 patients with Wolff-Parkinson-White syndrome after intravenous (1 mg kg-1 in 60 minutes) and oral administration of two dose regimens (75 and 150 mg daily). Under control conditions atrial fibrillation (AF) with a rapid ventricular response was induced in all patients and atrioventricular reciprocating tachycardia (AVRT) in 9 patients. After intravenous encainide AF was no longer induced in 3/9 patients; in 3 of the remaining the accessory pathway (AP) was totally blocked and in the others the shortest RR interval increased from 213 +/- 6 to 297 +/- 91 ms and the mean RR interval from 293 +/- 39 to 362 +/- 79 ms. The lower dose of oral encainide prolonged the shortest RR interval from 206 +/- 24 to 273 +/- 64 ms and the mean RR interval from 280 +/- 48 to 368 +/- 52 ms in 6 patients; in 2 cases no preexcited beats were recorded and in 1 AF was not inducible. After the higher dose of oral encainide AF was still inducible in 7/8 cases; in 3 the AP was blocked and in the others the shortest and mean RR intervals increased from 202 +/- 30 to 280 +/- 24 ms and from 276 +/- 59 to 436 +/- 80 ms, respectively. After intravenous encainide antegrade conduction over the AP was blocked in 4/9 patients and the antegrade effective refractory period (ERP) was prolonged in another 4. Oral encainide blocked AP conduction in 4 cases and prolonged ERP considerably in the others.(ABSTRACT TRUNCATED AT 250 WORDS)