Assessment of left ventricular regional work under ischemia

The wall tension-regional area (T-A) loop method, a new approach assessing regional contractile function of the left ventricle, has been developed in experiments performed on the isolated dog heart. Regional work is quantitatively determined by the area within a T-A loop with physically correct dimensions of energy (Joule) and regional contractility can be reliably assessed by the end-systolic T-A relation (ESTAR). During global ischemia, both the T-A loop area and the slope of the linear ESTAR decreased in proportion to the decreases in left ventricular stroke work and contractility. During regional ischemia, the T-A loop area in an ischemic region decreased to near zero, and the ESTAR markedly shifted to the right with a decreased slope and an increased regional area intercept. In contrast, the T-A loop in a non-ischematic region showed an increase in systolic area shrinkage and a decrease in regional work, demonstrating hyperkinesis due to regional afterload reduction. In addition, the ESTAR in a non-ischemic region remained almost unchanged. Thus, using the T-A loop method we can reliably assess regional work and contractility of a left ventricular region under ischemia.