Regional pressure-length relations during acute myocardial ischaemia and prolonged post-ischaemic dysfunction (stunning)
The effects of acute myocardial ischaemia and reperfusion were studied on regional myocardial function in 10 pigs subjected to fentanyl-pentobarbital anaesthesia. Regional function was defined by pressure-length characteristics in the myocardium supplied by the left anterior descending coronary (LAD) artery and left circumflex coronary (LX) artery. The LAD artery was occluded for 15 minutes and reperfused for 120 minutes thereafter. Acute ischaemia shifted the pressure-length loop to the right and reduced regional systolic shortening while post-systolic shortening (diastolic dysfunction) occurred. Reperfusion was associated with arrhythmias that required lignocaine and direct defibrillation in all the animals. During reperfusion the end-systolic pressure-length relationship was similar to that registered during the control period (before ischaemia) but was left shifted as gauged by a decrease in the extrapolated length intercept at zero ventricular pressure. Decreased regional systolic shortening and post-systolic shortening persisted during reperfusion. Results indicated that myocardial stunning is associated with progressive stiffening of the reperfused myocardium, reduced systolic function and significant diastolic dysfunction.