AJP - Heart and Circulatory Physiology, Vol 256, Issue 3 672-H680, Copyright © 1989 by American Physiological Society
Effect of myocardial ischemia on hemodynamic response to carotid occlusion
G. E. Billman and D. H. Marsh
Department of Physiology, Ohio State University, Columbus 43210.
Fourteen mongrel dogs were anesthetized and instrumented to measure
arterial pressure (AP), left ventricular pressure (LVP), aortic blood flow,
and heart rate (HR). Hydraulic occluders were placed around the left
anterior descending (LAD, n = 9) and left circumflex (LCC, n = 14) coronary
arteries. A bilateral carotid occlusion (BCO) was made before and during
either anterior (LAD occlusion) or posterior (LCC occlusion) ischemia.
Posterior ischemia significantly (P less than 0.01) reduced the BCO-induced
increases in mean AP (by 44.3 +/- 7.3%), systolic LVP (by 65.5 +/- 6.9%),
first derivative of LVP (dLVP/dt, by 95.7 +/- 44.3%), and aortic resistance
(by 117.7 +/- 26.9%). In contrast, anterior ischemia failed to alter
significantly the hemodynamic response to BCO. Bilateral vagotomy
attenuated or eliminated many of the effects of posterior ischemia on the
BCO response. In fact, the change in aortic resistance was no longer
affected by the ischemia and increased to the same extent, as noted during
the control BCO. However, mean AP (38.7 +/- 6.8%), systolic LVP (40.3 +/-
8.7%), and dLVP/dt (62.4 +/- 11.0%) remained significantly reduced when
compared with the control (no coronary occlusion) response. These data
suggest that 1) posterior ischemia elicits a greater reduction in the BCO
response than anterior ischemia, and 2) vagal afferents as well as
depression of contractile function may both contribute to the BCO response
inhibition noted during posterior ischemia.
