BackgroundLoad‐dependent impairment of left ventricular (LV) function was observed after leg elevation in a subgroup of coronary surgery patients. The present study investigated underlying mechanisms by comparing hemodynamic effects of an increase in LV systolic pressures with leg elevation to effects of a similar increase in systolic pressures with phenylephrine.MethodsThe study was performed in patients undergoing elective coronary surgery prior to cardiopulmonary bypass. High‐fidelity LV pressure tracings (n = 25) and conductance LV volume data (n = 10) were obtained consecutively during leg elevation and after phenylephrine administration (5 [micro sign]g/kg).ResultsLeg elevation resulted in a homogeneous increase in end‐diastolic volume. The change in stroke volume (SV), stroke work (SW) and dP/dtmaxwas variable, with an increase in some patients but no change or a decrease in other patients. For a matched increase in systolic pressures, phenylephrine increased SW and dP/dtmaxin all patients with no change in SV. Load dependence of relaxation (slope R of the [Greek small letter tau]‐end‐systolic pressure relation) was inversely related for changes in SV, SW, and dP/dtmaxwith leg elevation but not with phenylephrine.ConclusionsThe different effects of leg elevation and phenylephrine suggest that the observed decrease in SV, SW, and dP/dtmaxwith leg elevation in some patients could not be attributed to an impaired contractile response to increased systolic LV pressures. Instead, load‐dependent impairment of LV function after leg elevation appeared related to a deficient length‐dependent regulation of myocardial function.