Ischaemic contracture and myocardial perfusion in isolated rat heart

The development of left ventricular contracture and myocardial perfusion defect was studied in isolated rat hearts during global ischaemia of 90 min duration. The left ventricular pressure was measured by a balloon catheter inserted into the ventricle and filled with water. The pressure reached the maximum at 16 min of ischaemia. The left ventricular volume and compliance (passive distensibility) were measured by the same balloon, the former by connecting the balloon to an open catheter and the latter by applying a constant additional volume (0.020 ml) into the balloon. the left ventricular volume and compliance both decreased progressively for 20 min of ischaemia after which they remained low for the rest of the observation period (90 min). The myocardial perfusability was tested by infusing 0.1 per cent sodium fluorescein in isotonic saline into the cannulated aortic root of the isolated heart preparation. The percentage perfused with the fluorescent tracer in horizontal frozen myocardial sections was estimated by point counting from colour photogragraphs taken under ultraviolet light. The proportion of the perfused area decreased gradually from 100% at 0 min of ischaemia to 93, 67, 43 and 37% at 15, 30, 60 and 90 min of ischaemia, respectively. It was concluded that ischaemic contracture of the left ventricle is followed by the development of a myocardial perfusion defect in isolated ischaemic rat heart.