I investigated the relation of the maximum rate of left ventricular pressure rise to the end-diastolic volume and the comparison of the maximum rate of left ventricular pressure rise-end-diastolic volume relation to the end-systolic pressure-volume relation, using the time-varying elastance model. These studies were performed in 11 dogs chronically instrumented to measure left ventricular pressure and determine left ventricular volume from three orthogonal dimensions. During vena caval occlusions, the relations between the maximum rate of left ventricular pressure rise and end-diastolic volume were described by straight lines (r = 0.97 +/- 0.01, mean +/- SD). Dobutamine increased the slope of the maximum rate of left ventricular pressure rise-end-diastolic volume relation to 358 +/- 94% of control. This increase was greater than the 244 +/- 61% increase in the slope of the end-systolic pressure-volume relation (P less than 0.005). The volume intercepts of the maximum rate of left ventricular pressure rise-end-diastolic volume relation and end-systolic pressure-volume relation were similar and were not significantly altered by dobutamine. The ratio of the slope of the maximum rate of left ventricular pressure rise-end-diastolic volume relation to the slope of the end-systolic pressure-volume relation divided by the time from end-diastole to end-systole was similar before (2.2 +/- 0.7) and after dobutamine (2.3 +/- 0.7, P = NS). Angiotensin II did not significantly alter the maximum rate of left ventricular pressure rise-end-diastolic volume relation generated by caval occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)