Interaction between left ventricular end-diastolic and end-systolic volumes in normal humans.

The extent to which the end-systolic volume (ESV) "follows" the end-diastolic volume (EDV) when the latter changes in response to various perturbations is a major determinant of the cardiac ejection fraction (EF) and has not been studied in humans. We measured EDV, ESV, and EF, determined by gated blood pool scans, during a change in posture from the supine to the upright seated position and during graded upright bicycle exercise. The experimental group consisted of 119 healthy individuals (79 males and 40 females) ranging in age from 21 to 81 yr and in physical-conditioning status (75-225 W maximum work load); rigorous screening excluded cardiac disease. Multiple regression analysis showed that the change in ESV (delta ESV) during a postural shift or during graded exercise was highly statistically correlated with the change in EDV (delta EDV) that occurred (r2 ranged from 0.34 to 0.49, correlation is positive) regardless of age, sex, or exercise work load. The correlation of delta ESV with delta EDV observed in this large sample, heterogeneous with respect to age, sex, and physical fitness, was also present in additional 31 subjects who exercised during beta-adrenergic blockade (propranolol 0.15 mg/kg). The delta EF with posture change and exercise in all subjects under all conditions was highly and inversely correlated with the delta ESV (r2 ranged from 0.38 to 0.81). Thus the delta ESV during the circulatory adaptive response to orthostatic and exercise stresses in humans is related to the delta EDV, and this relationship modulates the delta EF in response to these stresses.