Circulation, Vol 80, 1536-1543, Copyright © 1989 by American Heart Association
BB Lerman, RC Wesley and L Belardinelli
Exogenous adenosine has been shown to have potent electrophysiologic
effects and antiarrhythmic properties within the atrioventricular (AV)
node. Endogenous adenosine, a nucleoside with an increased release signaled
by ischemia and hypoxia, is not believed to exert significant effects
during homeostatic conditions. Recent experimental evidence suggests,
however, that under normoxic conditions, the amount of adenosine released
may be sufficient to mediate some of its physiologic effects. This study
was designed to test the hypothesis that in humans the electrophysiologic
effects of endogenously released adenosine on AV nodal conduction can be
demonstrated under normoxic conditions by inhibiting uptake and degradation
of the nucleoside. In the first protocol, the effects of intravenous
dipyridamole (0.56 mg/kg bolus i.v., 5 micrograms/kg/minute infusion), a
nucleoside-transport blocker that elevates endogenous plasma levels of
adenosine, on AV nodal conduction were evaluated in seven patients. At a
constant atrial paced cycle length, dipyridamole increased the AH interval
from 110 +/- 19 to 164 +/- 26 msec, p = 0.002 (+/- SEM). Aminophylline (5.6
mg/kg i.v.), a competitive antagonist of adenosine, completely reversed the
effects of dipyridamole on AV nodal conduction. Similarly, dipyridamole
increased the cycle length at which pacing-induced AV nodal Wenckebach
occurred, from 348 +/- 31 (control) to 388 +/- 33 msec (dipyridamole) (p =
0.002). In a second protocol, the effects of intravenous dipyridamole were
evaluated in another group of six patients who had supraventricular
tachycardia (SVT) in which the AV node was part of the reentrant
circuit.(ABSTRACT TRUNCATED AT 250 WORDS)
ARTICLES
Electrophysiologic effects of dipyridamole on atrioventricular nodal conduction and supraventricular tachycardia. Role of endogenous adenosine
Department of Medicine, University of Virginia Medical Center, Charlottesville.
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