Electrophysiologic and antiarrhythmic effects of intravenous bisoprolol in atrioventricular nodal reentry tachycardia

Beta-blockade may be useful in the termination and prevention of atrioventricular nodal reentry tachycardia (AVNRT), An electrophysiologic study was performed in 9 patients (4 men and 5 women; mean +/- SD age, 56 +/- 16 years) with documented AVNRT before and after the intravenous administration of 5 mg of bisoprolol, In 5 of the 9 patients, AVNRT was terminated by bisoprolol, and AVNRT could no longer be induced in 6 of the 9 patients, Bisoprolol significantly prolonged the Wenckebach cycle length but did not affect fast pathway refractoriness or atrioventricular (AV) nodal conduction time during sinus rhythm or various paced cycle lengths up to 430 milliseconds, Conversely, it significantly prolonged the mean atrium-His bundle (AH) interval during AVNRT from 244 +/- 65 milliseconds to 320 +/- 64 milliseconds, These observations suggest that the effects of bisoprolol on the AV node, primarily at short cycle lengths, are rate dependent, Due to AH prolongation, mean tachycardia cycle length significantly increased from 313 +/- 58 milliseconds to 378 +/- 50 milliseconds, but there was no difference in the relative amount of prolongation between responders (60.8 +/- 26 ms) and nonresponders (64.6 +/- 37 ms), Bisoprolol appears to be useful in the termination and prevention of AVNRT during programmed electrical stimulation studies, Its effects on the AV node are use dependent.