In-plane myocardial wall stress is not the primary determinant of coronary systolic flow impediment. A study in the isolated, perfused dog septum.

The hypothesis that ventricular in-plane tensile wall stresses are the major determinant of systolic coronary flow was investigated in this study. We measured coronary artery inflow in the maximally vasodilated bed of the isolated beating septum (n = 10) during two modes of contraction characterized by markedly different levels of developed in-plane stress. An increase in contractility was induced by changing from the control steady-state pacing state to a postextrasystolic potentiated state induced by a modified rapid pacing protocol. Over a range of increments of passive stretch, the systolic flow impediment versus the diastolic wall strain was described by an inverse linear relation. Despite the differences in developed in-plane wall stresses between the two modes of contraction (p less than 0.001), the slope and intercept of these relations in both the control and potentiated states were not different for the low versus high developed stress modes. The systolic flow impediment versus diastolic wall st...