Circulation, Vol 89, 423-431, Copyright © 1994 by American Heart Association
MJ Reiter, Z Zetelaki, CJ Kirchhof, L Boersma and MA Allessie
BACKGROUND: Antiarrhythmic therapy of ventricular tachycardia is associated
with decreased efficacy and increased proarrhythmia in patients with
congestive heart failure, but the explanation for these observations is not
known. This study examined the interaction of ventricular dilatation and
d-sotalol in a model of reentry ventricular tachycardia. METHODS AND
RESULTS: Thin epicardial layers of anisotropic myocardium were created in
Langendorff-perfused rabbit left ventricles by a cryo procedure. A
fluid-filled, latex balloon was secured within the left ventricle to change
ventricular volume. Sustained reentrant ventricular tachycardia, around a
central cryolesion, was induced by rapid pacing in all preparations (n =
7). Epicardial mapping was performed through 248 electrodes. Single
premature beats introduced within the reentry circuit were used to define
the excitable gap. Dilatation did not influence ventricular tachycardia
cycle length or conduction velocity. A 1.25-mL increase in left ventricular
volume widened the excitable gap by 12% (range, 5% to 29%) (P < .001)
because of a decrease in myocardial refractoriness. d-Sotalol (final
concentration, 10 mg/L) narrowed the excitable gap 18% (range, 7% to 29%)
(P = .002) in the undilated left ventricle. d-Sotalol was less effective in
the dilated left ventricle, narrowing the excitable gap only 9%, a
difference that was not statistically significant. During pacing to induce
or terminate tachycardia, tachycardia acceleration was observed
significantly more frequently in the dilated than in the undilated
ventricle. Ventricular tachycardia acceleration was due to the development
of double-wave reentry (two successive waves traveling in the same circuit
in the same direction). d-Sotalol, which narrowed the excitable gap,
prevented tachycardia acceleration and double-wave reentry. CONCLUSIONS:
Antiarrhythmic efficacy may be decreased by dilatation because of widening
of the initial excitable gap and a decrease in the gap-narrowing effect of
these agents. Double-wave reentry, more likely with a widening of excitable
gap, may partially explain tachycardia acceleration in the dilated
ventricle.
ARTICLES
Interaction of acute ventricular dilatation and d-sotalol during sustained reentrant ventricular tachycardia around a fixed obstacle
Department of Physiology, University of Limburg, Maastricht, The Netherlands.
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