Mechanism of supraventricular tachycardia and pharmacological effects on it.

Electrophysiologic study in 30 patients with documented SVT, 16 of whom had preexcitation, and in 24 control subjects were reported. The mechanism of SVT were found to be various and to include reentry confined to the AV node, SA node or the atrium, reentry through accessory pathway and ectopic atrial automaticity. It was noted that some of SVT might use concealed accessory pathway in VA direction while the some of SVT in WPW syndrome might not utilize accessory pathways. Electrophysiological properties in cases with SVT did not differ from those observed in controls. There were no differences in the mode of electrophysiological action of drugs between XVT and control groups. Both propranolol and procaine amide slightly depressed AV conduction. However, the action of the drugs on echo zone were not the same. The basic mechanisms of the action of the drugs in SVT were discussed.