Effect of flecainide on regional left ventricular wall motion after acute intravenous, acute oral and chronic oral administration late after coronary artery bypass grafting

Intracoronary flecainide induces ST alternans and reentrant arrhythmia on intact canine heart: A role of 4-aminopyridine-sensitive current

BACKGROUND

The electrical alternans shown on an ST segment, ST alternans, is known as one of the most important predictors of ventricular fibrillation (VF). It has also been reported that sodium channel inhibition changes action potential configuration, especially on the repolarization phase. Thus, the sodium channel blocker may produce ST alternans and trigger reentrant arrhythmia.

METHODS AND RESULTS

A sodium channel blocker (disopyramide, lidocaine, or flecainide) was infused selectively into the left anterior descending coronary artery in anesthetized, open-chest dogs. Sixty unipolar electrograms were simultaneously recorded from the entire cardiac surface of the heart. The amplitude of ST alternans (STa) was determined as the difference in the ST-segment magnitude between 2 consecutive electrograms. We accepted the greatest STa among 60 leads for evaluation. High-dose flecainide (100 microg. kg-1. min-1) increased STa and evoked a spontaneous VF. The STa in high-dose flecainide loading (8.7+/-3.4 mV; mean+/-SEM) was significantly greater than that in disopyramide or lidocaine (0. 9+/-0.4 and 0.8+/-0.2 mV, P<0.05). Treatment of 4-aminopyridine (4-AP) suppressed the increase in STa and the occurrence of VF evoked by flecainide, while E4031 or verapamil did not inhibit those.

CONCLUSIONS

Flecainide caused the ST alternans that was closely correlated to the occurrence of VF. Because the ST alternans was suppressed by 4-AP treatment, a 4-AP-sensitive current such as Ito or Isus may play an important role on this phenomenon.

Oral flecainide, sotalol, and verapamil for the termination of paroxysmal supraventricular tachycardia

The ability to terminate supraventricular tachycardia (SVT) acutely with an oral dose of flecainide (2.5-3.3 mg/kg), sotalol (2.0-2.9 mg/kg), and verapamil (3.3-3.7 mg/kg) was investigated in an observational study of six patients with SVT normally controlled by an antitachycardia pacemaker. The pacemaker was programmed to induce SVT and the stability of SVT was observed for 90 minutes as a baseline. Subsequent studies involved testing of the three antiarrhythmic drugs on separate occasions, given in random order as crushed tablets in orange juice during pacemaker induced SVT, with plasma drug levels collected every 15 minutes for 90 minutes post drug ingestion. Sotalol produced drug induced slowing of SVT in all six patients, with termination of SVT in three patients by 60-65 minutes, with maximum plasma levels of 0.76-2.09 micrograms/mL achieved by 90 minutes. Flecainide produced maximum plasma levels of 83-745 ng/mL, 60-90 minutes post ingestion, and slowed SVT in three patients. SVT was terminated in three patients after 45-85 minutes, but no effect on SVT was seen in two patients who had inadequate plasma levels (< or = 166 ng/mL) from doses < 3 mg/kg. Verapamil produced maximum plasma levels of 0 (undetectable) to 388 ng/mL, 45-90 minutes post ingestion, and slowed SVT in three patients, but only one of these patients reverted to sinus rhythm (at 40 min). No effect on SVT was seen in three patients due to undetectable plasma levels. We concluded that sotalol (> or = 2 mg/kg) and flecainide (> or = 3 mg/kg) appeared to be suitable oral drugs for termination of SVT.(ABSTRACT TRUNCATED AT 250 WORDS)