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)

Potential functions of plasma prorenin; regional activation and tissue extraction.

The fate of circulating inactive prorenin was examined in patients and volunteers. Prorenin was activated either by acid-dialysis with warming at pH 3.3 or with trypsin. The results were similar but omission of warming reduced the value by 13%. In 6 volunteers, 20 min forearm venous occlusion raised regional total (T) and inactive (I) plasma renin concentration (PRC) by 51% and 48% without change of active (A) renin. During intense forearm exercise the ratio APRC: IPRC did not change in muscle or skin venous blood. Body anaerobic exercise increased APRC 3.7-fold without change in IPRC. These procedures activate plasminogen but are without effect on prorenin. In 18 patient with stable angina, TPRC was lower in coronary sinus than arterial blood (p less than 0.001) but APRC was not affected. A-V differences were not detected across the leg. Prorenin is apparently stable in the circulation but extracted by the heart.