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Abstract
Release of left anterior descending coronary artery ligature was performed in 32 dogs
after periods of ligation ranging from 3 to 45 minutes. Spontaneous ventricular tachycardia
or fibrillation occurred during occlusion in 9 of 20 dogs, developing during the first
8 minutes of occlusion in 8 of the 9. Ventricular tachycardia or fibrillation was
evoked by release of occlusion in 3 of 7 dogs after a short-term occlusion of 3 to
6 minutes, and in 9 of 13 dogs after release of a long-term occlusion of 15 to 45
minutes. Thresholds for induced ventricular tachycardia or fibrillation were obtained
using a train of gated stimuli (100 Hz for 250 msec). During short-term occlusions,
average thresholds for ventricular tachycardia or fibrillation were reduced from 32.4
ma (control) to 3.4 ma (P < 0.001); during long-term occlusions, thresholds returned to normal (control 29.6
ma, occlusion 18.6 ma; difference not significant). Immediately after release of both
short- and long-term occlusions, thresholds were not significantly different from
control values. No correlation was found between mechanical and electrical abnormalities
during the release phase since the magnitude of tension prolongation after release
of both short- and long-term ligations was the same and thus did not correspond with
the electrical differences of these states.
Our data suggest the following conclusions: (1) The time course of spontaneous ventricular
vulnerability to fibrillation during coronary occlusion differs from that of ligature
release, the former diminishing and the latter increasing with the duration of occlusion.
(2) This observation and the lack of correlation between thresholds of induced ventricular
tachycardia or fibrillation and spontaneous vulnerability to fibrillation after ligature
release suggest different electrophysiologic mechanisms for ventricular tachyarrhythmias
during and after release of coronary ligation.
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Article info
Publication history
Accepted:
November 28,
1973
Footnotes
☆This work was supported by Contract Grant 71-2479 and Research Grant 7139, from the National Heart and Lung Institute, National Institutes of Health, Bethesda, Md.
Identification
Copyright
© 1974 Published by Elsevier Inc.
