[Regional coronary outflow and coronary reserve assessed by the thermodilution technique: an experimental study]

Coronary blood flow distribution and coronary flow reserve were experimentally evaluated by the thermodilution technique. Using a special catheter with two external thermistors 5 cm apart, the great cardiac vein (GCV) outflow and coronary sinus (CS) outflow were measured. Coronary inflows in the left anterior descending (LAD) and circumflex (LCX) arteries were measured by electromagnetic flow probes during arterial occlusion or bolus arterial injection of nitroglycerin and dipyridamole injection in a peripheral vein. On the LAD side, the venous flow due to the interventions increased both GCV and CS outflows, while the interventions in the LCX increased CS outflow without significant changes in the GCV flow. LAD inflow and GCV outflow, and LCX inflow and (CS-GCV) flow correlated well, and there were significant close correlations between each inflow and outflow. Coronary reserve in the LAD and LCX was studied in successive 70% and 90% stenoses produced by a calibrated constrictor. Maximal coronary flow was obtained during reactive hyperemic response after coronary artery occlusion. Although there was no significant coronary reserve in the coronary inflow or outflow in the basal state, coronary reserve in the GCV and CS decreased significantly in stenoses of the LAD and LCX. These results suggest that this method allows practical assessment of drainage from the LAD and LCX areas and that stenosis greater than 70% can be estimated from the changes in regional venous outflows. This method may be helpful in evaluating regional coronary hemodynamics clinically.