Simultaneous determination of left ventricular end-systolic pressure-volume and pressure-dimension relationships in closed-chest dogs

Abstract

The left ventricular end-systolic pressure-volume relationship is a load-insensitive measure of left ventricular performance. The relationship at end-systole between left ventricular pressure and dimension is more easily obtained, but the conflicting results of previous studies make it unclear if it has the same properties as the left ventricular end-systolic pressure-volume relationship. To address this issue, 11 dogs were instrumented to measure left ventricular pressure and three orthogonal left ventricular dimensions. Left ventricular pressure and dimensions were varied by use of caval occlusion. Left ventricular volume was calculated as an ellipsoid. The left ventricular end-systolic pressure-volume relationship and each of the three end-systolic pressure-dimension relations were described by straight lines (r = .97 ± .02, mean ± SD). In 6 animals, dobutamine produced similar significant increases (p < .01) in the slope of the end-systolic pressure-volume relationship (244 ± 61% of control), the end-systolic pressure-anterior-posterior dimension relationship (248 ± 89%), the end-systolic pressure-septal-lateral dimension relationship (211 ± 95%), and the end-systolic pressure-basal-apical dimension relationship (210 ± 85%). The intercepts at zero pressure were relatively unchanged by dobutamine. In contrast, occlusion of the distal left anterior descending coronary artery in 5 animals produced a rightward shift of the left ventricular end-systolic pressure-volume relationship and the pressure-basal-apical dimension relationship, while the pressure-anterior-posterior dimension and pressure-septal-lateral dimension relationships were relatively unaffected. We conclude that the relationships between left ventricular end-systolic pressure and volume and left ventricular end-systolic pressure and each of three orthogonal left ventricular dimensions respond in a similar manner to global changes in contractility, but display different responses to regional ischemia. Thus, left ventricular end-systolic pressure-dimension relationships may be used to assess global but not segmental changes in left ventricular performance.