Background and Objective
A robust release of endothelin-1-1 (ET) with subsequent ETA subtype receptor (ET-AR) activation occurs in patients following cardiac surgery requiring cardiopulmonary bypass (CPB). Increased ET-AR activation has been identified in patients with poor LV function (reduced ejection fraction; EF). Accordingly, this study tested the hypothesis that a selective ET-AR antagonist (ET-ARA) administered peri-operatively would favorably affect post-CPB hemodynamic profiles in patients with a pre-existing poor LVEF.
Methods and Results
Patients (n=29; 66±2 yrs) with a reduced LVEF (37±2%) were prospectively randomized, in a blinded fashion, at the time of elective coronary revascularization and/or valve replacement requiring CPB, to infusion of the highly-selective and potent ET-ARA, sitaxsentan at 1 or 2 mg/kg (IV bolus; n=9, 10 respectively) or vehicle (saline; n=10). Infusion of the ET-ARA/vehicle was performed immediately prior to separation from CPB and again at 12 hrs post-CPB. ET and hemodynamic measurements were performed at baseline, at separation from CPB (Time 0) and at 0.5, 6, 12, 24 hrs post-CPB. Baseline plasma ET (4.0±0.3 fmol/mL) was identical across all 3 groups, but when compared to pre-operative, baseline values obtained from age matched subjects with a normal LVEF (n=37;LVEF>50%), were significantly increased (2.9±0.2 fmol/mL, p<0.05) Baseline systemic (SVR; 1358±83 d·s·cm-5) and pulmonary (PVR; 180±23 d·s·cm-5) vascular resistance were equivalent in all 3 groups. As a function of Time 0, SVR changed in an equivalent fashion in the post-CPB period, but a significant ET-ARA effect was observed for PVR (ANOVA; p<0.05). For example at 24 hrs post-CPB, PVR increased by 40 d.scm-5 in the vehicle group, but directionally decreased by over 40 d·s·cm-5 in the 2 mg/kg ETARA group (p<0.05). Total adverse events were equivalently distributed across the ET-ARA/placebo groups.
Conclusions
These unique findings demonstrated that infusion of an ET-ARA in high risk cardiac surgery patients was not associated with significant hemodynamic compromise. Moreover, ET-ARA favorably affected PVR in the early post-operative period. Thus, the ET-AR serves as a potential pharmacological target for improving outcomes following cardiac surgery in patients with compromised LV function.