Magnesium-supplemented warm blood cardioplegia in patients undergoing coronary artery revascularization

BACKGROUND: Although there is growing evidence to suggest that the administration of magnesium (Mg2+) to patients undergoing coronary artery bypass grafting (CABG) and to patients after myocardial infarction is beneficial, the addition of Mg2+ to cardioplegic solutions remains controversial. The aim of this study was to compare the effects of intermittent warm blood cardioplegia with and without Mg2+ supplementation on the early postoperative clinical outcomes in patients undergoing both elective or urgent CABG. METHODS: Four hundred patients undergoing CABG were prospectively randomized to receive either blood cardioplegia without Mg2+ (BC, n = 200) or supplemented with Mg2+ (BC-Mg2+, n = 200). Serial plasma Mg2+ concentrations were recorded at base line and postoperatively from days 1 to 4. RESULTS: Patient characteristics were similar and no significant differences were found in early mortality and morbidity in the two groups. Analysis of 178 patients undergoing urgent CABG for unstable symptoms (BC = 95, BC-Mg2+ = 83) demonstrated a significantly lower requirement for internal defibrillation and temporary epicardial pacing in the BC-Mg2+ group. Furthermore, there was a nearly twofold lower incidence of new postoperative atrial fibrillation in the BC-Mg2+ group compared with the BC group (19% versus 34%, p = 0.03). Postoperative plasma Mg2+ levels were consistently lower in those patients who developed new postoperative atrial fibrillation compared with those who did not (p = 0.05). CONCLUSIONS: The addition of Mg2+ to warm blood cardioplegia resulted in a lower incidence of intraoperative and postoperative arrhythmias in patients undergoing urgent CABG for unstable angina.