Integrated regional work equals total left ventricular work in regionally ischemic canine heart

Abstract

To assess left ventricular (LV) regional work with physically correct dimensions, wall tension-regional area (T-A) loops were analyzed before and after coronary occlusion in the excised cross-circulated canine LV (n = 11) connected to a volume-servo pump. Wall tension was calculated with the force equilibrium equation for a sphere, and regional areas were determined from pairs of orthogonal sonomicrometers in ischemic and nonischemic regions. LV and regional stroke work were simultaneously assessed from the pressure-volume and T-A loops during one cardiac cycle at various end-diastolic and stroke volumes. After coronary occlusion, regional work of the ischemic region markedly decreased to near or even below zero. Although regional work of the nonischemic region moderately decreased at constant LV end-diastolic and stroke volumes, the contribution of the nonischemic region to LV stroke work increased. Globally integrated regional work calculated from regional work/unit area and estimates of the extent of ischemia closely agreed with measured LV stroke work either before (n = 119; r = 0.92) or after coronary occlusion (n = 141; r = 0.93) despite the marked changes in regional work in both regions. We conclude that the global integral of regional work equals the total LV work and that regional work of the LV can be reliably assessed from the T-A loop with the same dimensions as energy in both normal and regionally ischemic hearts.