Development of collateral function with repetitive coronary occlusion in a canine model reduces myocardial reactive hyperemia in the absence of significant coronary stenosis.

The present study was designed to elucidate the role of collateral development, per se, on reactive hyperemia without persistent coronary stenosis in instrumented conscious dogs. Functional states of coronary collaterals were augmented by repetitive 2 minutes of coronary occlusion every 30 minutes for 2-9 days. Regional shortening measured sonomicrometrically recovered from -1.2 +/- 6.5% of the preocclusive state at the end of the first coronary occlusion to 100.5 +/- 1.2% (n = 8, P less than 0.01) after repeated coronary occlusions. Before and after collateral development, transient coronary occlusions of 5, 10, 20, 30, 60, 90, and 120 seconds were randomly performed. The degree of regional dysfunction and the following reactive hyperemic response were measured. Up to 20 seconds of coronary occlusion, the flow ratio and duration of coronary reactive hyperemia increased similarly, both before and after collateral development. However, when the duration of coronary occlusion was over 30 seconds, flow ratio and debt repayment ratio were reduced progressively after the collateral development. Among the indices exhibiting reactive hyperemia, debt repayment ratio decreased initially and correlated well with the recovery of regional dysfunction during coronary occlusion. Thus, the augmentation of collateral function after repetitive coronary occlusion reduces reactive hyperemia even in the absence of significant coronary stenosis.