Coronary hemodynamics during brief coronary occlusions at different levels of collateral function in conscious ponies. Williams, David O., Roger B. Boatwright, Karla S. Rugh, Chris R. Ross, R. Dustan Sarazan, Harold E. Garner, and Douglas M. Griggs, Jr. Department of Physiology and Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri, 65211
APStracts 2:0487H, 1995.
Adult grade ponies were surgically instrumented with a Doppler flow probe and pneumatic cuff occluder on the left anterior descending coronary artery (LAD), sonomicrometry crystals and intraventricular micromanometer in the left ventricle, and catheters in the left atrium, anterior interventricular vein, and, in some animals, the LAD. Conscious animal studies were begun 2 weeks after surgery. Measured variables included regional left ventricular systolic function, end diastolic wall thickness, oxygen extraction, lactate extraction, and hydrogen ion release. Changes in collateral perfusion were deduced from changes in these variables. Serial data were obtained during a 3 min LAD occlusion prior to stimulation of collateral function by the intermittent coronary occlusion method, and during a 10 min LAD occlusion after 14 +/- 2 days and 27 +/- 2 days of stimulation. Hemodynamic interpretation of data was based on a model of the equine coronary circulation consisting of collateral and arteriolar resistances in series. It was concluded that: 1) chronic stimulation of collateral function leads to the emergence of a time-dependent reduction in total collateral resistance during acute coronary occlusion, 2) with enhancement of collateral function, the major resistance controlling collateral blood flow shifts from the collateral circulation to the recipient vessel arterioles, and 3) at a certain level of enhanced collateral function, coronary occlusion results in a triphasic blood flow response in collateral -dependent myocardium consisting of early hypoperfusion, transient hyperperfusion, and late autoregulated perfusion. This study demonstrates that chronic stimulation of collateral function is accompanied by specific alterations in coronary hemodynamics during acute coronary occlusion that hasten the recovery of ischemic myocardium. 

Received 24 March 1995; accepted in final form 19 October 1995.
APS Manuscript Number H290-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95