Coronary Collateral Growth in Canine Model with Gradual Coronary Stenosis and with Repetitive Coronary Occlusions

Summary

The time course of coronary collateral growth in gradual coronary stenosis due to an ameroid constrictor, and in repetitive coronary occlusions, was examined functionally in a canine model. Dogs were instrumented under sterile surgery with pairs of 5 MHz piezo-electric crystals at the left anterior descending artery (LAD) and left circumflex artery (LCX) perfusion area, and a miniature pressure transducer into the left ventricular cavity along with a flow probe and a cuff occluder on the LCX. In an ameroid model, an X-ray transparent ameroid constrictor was placed on the LCX. Repetitive coronary occlusions were controlled by an AM/AM telemetry system while left ventricular pressure and regional wall motion were continuously recorded via an FM/FM telemetry system. Regional wall motion before and during brief coronary occlusion was serially measured in an awake dog until the collateral growth reached the level of functional maturation. Amelioration of regional hypokinesis during transient coronary occlusion was augmented after a certain period of nonrecovery not only in the ameroid model, but also in the repetitive occlusion model. The duration of the lag phase in the model of gradual coronary stenosis was determined by the time needed for the progression of coronary stenosis to more than 80%. The lag phase was also noted in the repetitive occlusion model; however, the biological reason for the lag remains unclarified. A unifying mechanism for the growth of epicardial coronary collateral vessels in both the ameroid and the repetitive occlusion models will be examined over the time course of collateral vessel growth.