Systolic and diastolic pressure-volume relationships during cardiac surgery

Seven patients undergoing elective coronary artery bypass surgery were studied to assess left ventricular (LV) performance by pressure-volume loops. LV pressure was measured by micromanometry and instantaneous LV volume by a conductance catheter. Continuous pressure-volume relationships were determined during preload reduction before and after cardiopulmonary bypass (CPB). End-systolic elastance (Ees), as the slope of the end-systolic pressure-volume relationship (ESPVR), and diastolic elastance (Ed) were calculated from these interventions. Changes in position of the Ees were assessed at V75, the value of LV end-systolic volume at 75 mm Hg of LV pressure. From pre-CPB to post-CPB, Ees increased in three patients with a decrease of V75 in two patients, and Ees decreased in four patients with a concomitant increase in V75. Ed increased significantly (P less than 0.01) following CPB, demonstrating a decrease of ventricular distensibility. It is concluded that continuous measurement of LV pressure-volume relationships using the conductance catheter is feasible and may be a useful tool to estimate LV performance during cardiac surgery.