Myocardial ischaemia in patients with impaired left ventricular function undergoing coronary artery bypass grafting — milrinone versus nifedipine

Abstract

Background and objective: Myocardial ischaemia and infarction are major complications immediately after coronary artery bypass grafting. They may be due to incomplete surgical revascularization, perioperative anaesthetic management or vasospasm of arterial grafts, e.g. the internal mammary artery. Infusions of nifedipine or milrinone have been advocated to prevent spasm of the mammary artery. The study compared the incidence of myocardial ischaemia after continuous infusion of either nifedipine (0.2 µg kg⁻¹ min⁻¹) or milrinone (0.375 µg kg⁻¹ min⁻¹) in patients with compromised left ventricular function scheduled for elective coronary artery bypass graft.

Methods: After Institutional Review Board approval, this double-blinded randomized clinical study enrolled 30 adult patients with compromised left ventricular function (ejection fraction <0.4) scheduled for elective coronary artery bypass grafting after written informed consent had been obtained. Ischaemia was detected by Holter electrocardiographic monitoring. The incidence of myocardial cell death was monitored by serial determinations of the creatine kinase-MB (CK-MB) and troponin-I.

Results: New ST elevation ≥0.2 mV or new ST depression ≤0.1 mV occurred in five of 15 patients in the milrinone group (33.3%) and in 13 of 15 patients (86.6%) in the nifedipine group (P < 0.05). There were increases in CK-MB and troponin-I in both groups. Twenty-four hours postoperatively, CK-MB (P = 0.003) and troponin-I (P = 0.001) were significantly higher in the nifedipine group.

Conclusions: Perioperative continuous infusion of milrinone, compared with nifedipine, results in a significantly lower incidence of myocardial ischaemia and myocardial cell damage after elective coronary artery bypass grafting.