Left Ventricular Function during Acute Regional Myocardial Ischemia in the Conscious Dog.

摘要

The effects of acute 1-min occlusion of the left circumflex coronary artery on the inotropic state and performance of the left ventricle were examined in adult mongrel dogs. The inotropic state, as indicated by changes in the maximum derivative of left ventricular pressure in the preejection phase and the maximum derivative of the transverse internal diameter, were diminished during the ischemic period. The end-systolic diameter increased 3.8 + or - 0.6 mm while the end-diastolic diameter increased only 0.4 + or - 0.2 mm, although the end-diastolic pressure increased 6.9 + or - 0.6 mm Hg. Progressive decreases in the stroke volume paralleled the apparent reduction in myocardial fiber shortening in the transverse plane. Cardiac output and arterial pressure declined, concurrently, thus maintaining a constant peripheral resistance during the occlusion. Acute coronary occlusion also caused an apparent increase in the myocardial wall stiffness as judged by the increase in the slope a of the equation dP/dV = aP + B, the increase of the slope of the pressure-diameter relationship, and the decrease in the rate of lengthening of the diameter during diastole. These findings suggest that acute myocardial ischemia results in an immediate reduction in the effective inotropic state and an apparent increase in the myocardial wall stiffness in the transverse plane. Both of these changes resulted in a decrease in performance of the left ventricle. (Author)