Simulation studies of the ischemic vulnerability of the subendocardium.

Changes in the subendo-subepi flow ratio were studied by using a simple electronic circuit model of the coronary vessel consisting of a resistor, capacitor and field effect transistor in order to provide a better understanding of the ischemic vulnerability of the subendocardium. The simulated subendo-subepi flow ratio was found to be approximately 1.2 under normal condition. Changes in the flow ratio were observed while varying the main arterial resistance, mean arterial pressure and intramyocardial pressure individually. The mean flow in the subendocardium was found to decrease at a rate faster than that in the subepicardium with the increase in the septal arterial resistance and the intramyocardial pressure. The same tendency was also observed while the arterial pressure was lowered. This decrease in the mean subendocardial flow is considered to be the effect of higher end-systolic resistance in the subendocardial venule compared to that in the subepicardial venule. These results would be helpful in understanding the vulnerability of the subendocardium to ischemia and in providing clinical treatment to patients with that disease.