AJP - Heart and Circulatory Physiology, Vol 235, Issue 6 628-H636, Copyright © 1978 by American Physiological Society
Myocardial perfusion and function during acute right ventricular systolic hypertension
M. Manohar, G. E. Bisgard, V. Bullard, J. A. Will, D. Anderson and J. H. Rankin
Hemodynamics, myocardial function, and regional myocardial blood flow (MBF)
were measured in 6 closed-chest ponies anesthetized with ketamine
hydrochloride before (control) and after creation of acute right
ventricular systolic hypertension (RVSH) during normoxia and isocapnic
hypoxia. The right ventricular (RV) systolic pressure during each RVSH
approached 90 mmHg. There were significant alterations in the pattern of
total ventricular MBG distribution in favor of the RV. Because RV
myocardium received proportionate increments to its endocardium as well as
epicardium, it is concluded that autoregulation in the RV coronary vascular
bed had not been abolished even during hypoxia + RVSH. Marked increase in
MBF to the right side of the septum during each RVSH with little change in
perfusion to other regions suggests that RV contraction is supported by the
right side of the septum. Because these increments occurred with decreased
RV coronary driving pressure they were the consequence of compensatory
coronary vasodilatation. The slow heart rate of the pony in the presence of
a large coronary vasodilatory reserve may have been the major factor in
allowing large increments in MBF to the stressed regions despite decreased
coronary driving pressure.
