Coronary transport reserve in normal dogs.

This study was designed to determine an acceptable method for producing maximal coronary vasodilation for quantifying coronary blood flow reserve and coronary capillary transport reserve. The anterior descending branch of the left coronary artery was cannulated and pump-perfused while aortic, central venous, and coronary perfusion pressures, heart rate, electrocardiogram, blood gases, and coronary blood flow (CBF) were continuously monitored. All parameters were measured at four to six points along the coronary pressure-flow autoregulation curve. Myocardial extraction and permeability-surface area products (PS) of 51Cr-ethylenediaminetetraacetic acid were determined with the single-injection indicator-diffusion method in intact working hearts of anesthetized dogs. Maximal vasodilations were produced with 2-min coronary occlusions and with intracoronary infusions of adenosine (ADO), dipyridamole, ADO + dipyridamole, papaverine, and ADO + alpha 1-receptor blockade. ADO was chosen to quantify coronary transport reserve because it produced maximal CBF's and PS's that were reproducible within and among animals and produced minimal effects on the cardiovascular system. Under base-line conditions, there was no relationship between PS and perfusion pressure. Base-line PS averaged 20 +/- 2 ml X min-1 X 100 g-1. Maximal vasodilation with constant CBF had no significant effect on PS. During maximal vasodilation, CBF and PS increased linearly with increasing perfusion pressure, and PS increased linearly with increasing plasma flow. Constant pressure maximal vasodilation with ADO caused PS to increase to 36 +/- 4 ml X min-1 X 100 g-1, and CBF was increased 380%.