A low magnesium level following bypass surgery is a major factor in determining survival. Coronary artery bypass graft surgery (CABG) is one of the most common operations performed in the United States with over half a million procedures performed in 1995. Unfortunately, the 1-year mortality rate is between 3 and 20% depending on the patient's health status prior to surgery. Researchers at Duke University Medical Center now report that the patient's magnesium status immediately following surgery is a major factor in determining 1-year survival. The study involved 957 patients undergoing primary CABG. All patients had their serum magnesium level measured daily during the 8 days following surgery. A magnesium level below 1.8 mmol/L was considered low. A total of 182 patients (19%) had a low magnesium level while the remaining 787 patients (81%) were categorized as having normal levels. One year following surgery 75 patients in the group of 957 had died and 22 had suffered a heart attack. The risk of death or a heart attack was 26% lower in the normal magnesium level group. Overall, patients with a magnesium level below 1.8 mmol/L during the first 8 days after surgery were twice as likely to have a heart attack (myocardial infarction) or to die within the first year after CABG as were patients with normal magnesium levels.
The researchers point out that serum magnesium levels are a very poor indicator of total body magnesium levels and that measuring intracellular levels would be more indicative. They found no relationship between magnesium levels and the incidence of atrial arrhythmias after the operation. The researchers speculate that the ability of magnesium to prevent postoperative death may be related to its ability to protect against free radical formation and to counteract the calcium overload inherent in reperfusion. Magnesium supplementation also reduces acute platelet dependent blood clotting and may help prevent ventricular arrhythmias. The researchers recommend that a clinical trial be carried out to investigate the benefits of magnesium treatment prior to CABG surgery.
Booth, John V., et al. Low serum magnesium level predicts major adverse cardiac events after coronary artery bypass graft surgery. American Heart Journal, Vol. 145, June 2003, pp. 1108-13
Editor's comment: This study supports the idea that magnesium is of prime importance for heart health. Other studies have shown that about a third of all North Americans are deficient in magnesium. Regular daily supplementation to ensure a minimum intake (dietary and supplemental) of about 400 mg/day of elemental magnesium would seem to be in order as an important preventive measure.