Introduction: This study evaluated whether intraoperative milrinone improves cardiac diastolic and systolic function in patients undergoing elective on-pump CABG.
Method: In this prospective study, 30 patients undergoing elective on-pump CABG were allocated equally to a milrinone group (n=15) or a control group (n=15). After anesthesia induction and before CPB, the milrinone group received a loading dose of 50 µg/kg over 10 minutes, followed by an infusion of 0.5 µg/kg/min continued for 6 hours postoperatively; the control group received an identical volume of normal saline. TEE was performed at two time points: after induction (baseline) and after separation from CPB. Baseline diastolic function was characterized using standard Doppler indices; however, patients were not preselected or stratified by diastolic dysfunction grade, which represents a limitation of the study design. Echocardiographic indices (fractional area change [FAC], pulmonary venous flow velocity [PV], deceleration time [DT], E/PV, A-wave duration [Adur], atrial reversal duration [ARdur]), hemodynamic variables, vasoactive requirements, and intensive care unit (ICU) length of stay were compared between groups.
Result: Baseline characteristics, including age, sex, weight, height, comorbidities, left ventricular ejection fraction (p=0.10), surgical duration (p=0.18), and CPB duration (p=0.10) were comparable between groups. Milrinone significantly increased FAC after CPB relative to control (55.39±10.86% vs 45.71±12.04%; p=0.028) and relative to its own baseline (vs 42.77±11.27%; p<0.001). Pulmonary venous flow velocity after CPB was significantly higher in the milrinone group than in controls (96.95±31.08 vs 76.03±22.54 cm/s; p=0.049) and higher than its own baseline (vs 63.59±20.72 cm/s; p<0.001). No significant between-group differences were observed in DT, E/PV, Adur, or ARdur. Hemodynamic parameters, norepinephrine requirement during CPB (p=0.92), inotrope and nitroglycerin dosing, cardiac rhythm, and ICU length of stay did not differ significantly between groups
Conclusion: Intraoperative milrinone significantly improved systolic performance (FAC) and pulmonary venous flow in patients undergoing elective on-pump CABG, with a relative improvement in selected diastolic indices and no adverse hemodynamic effects. However, because patients were not preselected for baseline diastolic dysfunction, the study was underpowered to detect a dedicated diastolic benefit. These findings suggest a potential role for milrinone in the perioperative management of CABG patients, particularly those with preexisting diastolic dysfunction. Adequately powered multicenter trials are warranted to confirm a dedicated diastolic benefit and to evaluate its impact on clinical outcomes, particularly in higher-risk or critically ill subpopulations.