Supraventricular Tachycardia in Patients Without Overt Preexcitation

Efficacy of intravenous sotalol for suppressing inducibility of supraventricular tachycardias at rest and during isometric exercise

The efficacy of intravenous sotalol (1 mg/kg) for suppressing inducibility of supraventricular tachycardias (SVT) with different electrophysiologic mechanisms was studied in 30 consecutive patients referred for an electrophysiologic study because of paroxysmal SVT. Orthodromic SVT using accessory atrioventricular (AV) connection was inducible in 14 patients, AV nodal reentrant SVT in 8, and intraatrial SVT in 8 before administration of sotalol, Isometric handgrip exercise facilitated the inducibility of SVT in 8 patients who were noninducible at rest. After intravenous sotalol, 7 of 14 patients (50%) with orthodromic SVT, 8 of 8 (100%) with AV nodal reentrant SVT, and 8 of 8 (100%) with intraatrial reentrant SVT became noninducible into sustained SVT, Isometric exercise facilitated the inducibility of only 3 nonsustained SVT runs after sotalol infusion, and exercise did not reverse the prolongation of refractory periods of the atrium, AV node, accessory pathway and ventricle caused by sotalol. During a mean follow-up period of 18 +/- 7 months, none of the 14 patients who remained noninducible into sustained SVT during the stress test after intravenous sotalol and tolerated long-term oral sotalol therapy had recurrence of symptomatic SVT. Thus, sotalol is efficacious for suppressing SVT with AV nodal or intraatrial reentrant mechanism, but less efficacious in patients with accessory AV pathway. The beta-blocking and cellular antiarrhythmic effects of sotalol are not significantly reversed by exercise.

Epinephrine-induced reversal of verapamil's electrophysiologic and therapeutic effects in patients with paroxysmal supraventricular tachycardia

The purpose of our study was to determine whether an infusion of epinephrine reverses the electrophysiologic effects of verapamil and whether reversal of verapamil's effects on the induction of paroxysmal supraventricular tachycardia (PSVT) by epinephrine during electropharmacologic testing is predictive of stress-related recurrences of PSVT during long-term treatment with verapamil. The infusion rates of epinephrine used in this study were 25 and 50 ng/kg/min, which previously have been demonstrated to result in plasma epinephrine concentrations in the range that occurs during a variety of stresses in humans. The subjects of this study were 17 patients with recurrent PSVT who underwent an electrophysiologic study in the control state and after at least 2 days of treatment with 240-480 mg/day verapamil. After assessing the response to verapamil, epinephrine was infused and testing was repeated. Verapamil significantly slowed atrioventricular conduction and prolonged refractoriness in the atrium and atrioventricular node. The effects of the two infusion rates of epinephrine were generally similar in magnitude and, therefore, the results were pooled. Epinephrine partially or completely reversed all of verapamil's electrophysiologic effects. Verapamil suppressed the induction of sustained PSVT in 15 patients. Epinephrine facilitated the induction of PSVT in seven of these 15 patients. All 15 patients were treated on a long-term basis with verapamil. The eight patients in whom epinephrine did not facilitate the induction of PSVT had no recurrences of PSVT during 9-18 months of follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)