Changes in myocardial contraction patterns in response to regional ischemia and sympathetic nerve stimulation.

We studied the effect of inferior cardiac nerve stimulation on global and regional left ventricular function before and after circumflex coronary arterial (CFX) occlusion in 12 pentobarbital-anesthetized cats. Regional function was evaluated by orthogonal sonomicrometry in the anterior midwall of the left ventricle and by two-dimensional short-axis echocardiography. CFX occlusion provoked hypokinesis in the nonischemic free wall adjacent to the dyskinetic ischemic region (17.6 +/- 2.3 vs. 34.6 +/- 2.2% preocclusion wall thickening; P < 0.01) and gradually improved systolic wall thickening toward the contralateral remote region, where the maximal hyperkinetic response was measured (52.9 +/- 4.4 vs. 32.5 +/- 3.3% preocclusion wall thickening; P < 0.001). In the anterior wall, remote region, hyperkinesis was predominant in longitudinal segments (8.1 +/- 0.8 vs. 2.3 +/- 0.6% preocclusion ejection shortening; P < 0.001) and slight in circumferential segments (11.0 +/- 0.7 vs. 9.1 +/- 0.6% preocclusion ejection shortening; P < 0.01). The postocclusion systolic wall thickening and segment-shortening pattern were not modified by sympathetic nerve stimulation, which increased cardiac output less after coronary occlusion, although contractility (dP/dt) increased markedly. In conclusion, the myocardial contraction pattern in ischemic and nonischemic regions after CFX occlusion is not much modified by sympathetic cardiac nerve stimulation.