REGIONAL PRESSURE-LENGTH RELATIONS DURING ACUTE MYOCARDIAL-ISCHEMIA AND PROLONGED POSTISCHEMIC DYSFUNCTION (STUNNING)

The effects of acute myocardial ischaemia and reperfusion were studied on regional myocardial function in 10 pigs subjected to fentanyl-pent obarbital anaesthesia. Regional function was defined by pressure-lengt h characteristics in the myocardium supplied by the left anterior desc ending coronary (LAD) artery and left circumflex coronary (LX) artery. The LAD artery was occluded for 15 minutes and reperfused for 120 min utes thereafter. Acute ischaemia shifted the pressure-length loop to t he right and reduced regional systolic shortening while post-systolic shortening (diastolic dysfunction) occurred. Reperfusion was associate d with arrhythmias that required lignocaine and direct defibrillation in all the animals. During reperfusion the end-systolic pressure-lengt h relationship was similar to that registered during the control perio d (before ischaemia) but was left shifted as gauged by a decrease in t he extrapolated length intercept at zero ventricular pressure. Decreas ed regional systolic shortening and post-systolic shortening persisted during reperfusion. Results indicated that myocardial stunning is ass ociated with progressive stiffening of the reperfused myocardium, redu ced systolic function and significant diastolic dysfunction.