AJP - Heart and Circulatory Physiology, Vol 239, Issue 5 658-H663, Copyright © 1980 by American Physiological Society
Improved performance of ischemic canine myocardium in response to nifedipine and diltiazem
J. E. Perez, B. E. Sobel and P. D. Henry
To characterize the effects of Ca2+ antagonists on the performance of the
ischemic myocardium, we administered nifedipine and diltiazem to
chloralose-anesthetized dogs with coronary artery occlusion and monitored
segmental myocardial shortening in ischemic and nonischemic zones with
implanted ultrasonic length gauges. Other dogs were treated with
nitroglycerin or nitroprusside for comparison. Dosage of all drugs was
adjusted to reduce mean aortic pressure by no more than 5 mmHg. Segmental
shortening was expressed as percent of control value before occlusion. In
control dogs (n = 8), shortening in ischemic zones 20 and 80 min after
occlusion averaged -16 +/- 2% and -17 +/- 2%, indicating paradoxical
elongation. With nifedipine (1 +/- 0.4 microgram . kg-1 . h-1; n = 8),
shortening of ischemic segments before treatment did not differ from
controls, but after 60 min of treatment was markedly improved, averaging 31
+/- 4% (P < 0.05). Diltiazem (10 +/- 2 microgram . kg-1 . h-1; n = 8)
produced a similar improvement in shortening in ischemic zones. However,
nitroglycerin (177 +/- 20 microgram . kg-1 . h-1; n = 8) and nitroprusside
(43 +/- 10 microgram . kg-1 . h-1; n = 8) failed to improve shortening in
ischemic regions. Thus, Ca2+ antagonists improved performance in ischemic
zones, but nitroglycerin and nitroprusside did not.
