Effect of regional ischemia on the left ventricular end-systolic pressure-volume relation in chronically instrumented...

The slope of the left ventricular end-systolic pressure-volume relation has been proposed as a sensitive index of left ventricular function since it increases in response to positive inotropic agents and decreases with global depression of contractility. The effect of a segmental depression of left ventricular contractile function produced by circumflex coronary artery occlusion on the left ventricular end-systolic pressure-volume relation was evaluated in seven chronically instrumented dogs. Left ventricular volume was calculated from three ultrasonically measured, orthogonal left ventricular endocardial dimensions. Left ventricular pressure was measured with a micromanometer. The left ventricular end-systolic pressure-volume relation was generated by occlusion of the inferior vena cava, before and after inducing regional ischemia, in the presence of autonomic blockade with propranolol and atropine. The end-systolic data in each dog, before and after coronary occlusion, were fit to the equation, P = E(V - V0), with r greater than or equal to 0.95 in all cases. Coronary occlusion shifted the left ventricular end-systolic pressure-volume relation to the right in each animal. During regional ischemia, the volume intercept (V0) increased from 10.1 +/- 7.8 to 20.4 +/- 9.8 ml (mean +/- SD) (p less than 0.005). The slope (E) of the left ventricular end-systolic pressure-volume relation was relatively unchanged. It is concluded that in intact dogs, regional left ventricular ischemia resulting from coronary occlusion produces a rightward shift of the left ventricular end-systolic pressure-volume relation.(ABSTRACT TRUNCATED AT 250 WORDS)