According to a study published in JAMA, the risk of heart attack or cardiovascular death was not reduced when patients were administered MC-1 before and for 30 days after coronary artery bypass graft surgery. MC-1 is a naturally occurring metabolite of vitamin B6 that prevents cellular calcium overload and may reduce ischemia-reperfusion injury.

Researcher John H. Alexander, M.D., M.H.S. (Duke University Medical Center, Duke Clinical Research Institute, Durham, N.C) and colleagues with MEND-CABG II (MC-1 to Eliminate Necrosis and Damage in Coronary Artery Bypass Graft Surgery Trial Phase II) write that, "Coronary artery bypass graft (CABG) surgery is one of the most important therapeutic options for relieving angina and improving survival and quality of life in patients with multivessel coronary artery disease. It is the most commonly performed cardiac surgical procedure in the world, and in 2005, more than 250,000 CABG procedures were performed in the United States."

CABG, however, puts patients at risk for serious complications such as heart attack, recurrent angina, kidney insufficiency, stroke, and death. Data from the Phase 2 trial have led researchers to suspect that in high-risk CABG surgery patients, treatment with MC-1 may reduce death or heart attack.

In this third phase of the trial, the researchers have developed a multicenter, randomized, double-blind, placebo-controlled design to evaluate the potential cardioprotective effect of MC-1 when administered before and continued for 30 days after CABG surgery. The sample consisted of 3,023 intermediate- to high-risk patients undergoing CABG surgery with cardiopulmonary bypass, and each participant was randomly assigned to an MC-1 treatment group or placebo group.

Results are summarized below:
9.3% (140 of 1,510) of the MC-1 group and 9.0% (133 of 1,486) of the placebo group experienced cardiovascular death or nonfatal heart attack at 30 days (non-significant difference) 1.0% of the MC-1 group and 0.3% of the placebo group died from any cause by 4 days (significant difference) 1.9% of the MC-1 group and 1.5% of the placebo group died from any cause by 30 days (non-significant difference) MC-1 did not prove beneficial in any subgroup (based on age, region of enrollment, or previous medical condition) or on other secondary outcome such as the incidence of postoperative stroke, atrial fibrillation, or kidney function. Similarly, patients in both groups had similar lengths of stay in hospitals and in intensive care units.

The researchers conclude: "MEND-CABG II demonstrates that among intermediate- to high-risk patients undergoing CABG surgery, MC-1, 250 mg/d, given immediately before and for 30 days following surgery did not reduce cardiovascular death or nonfatal [heart attack]. Myocardial injury remains a significant problem following CABG surgery. Effective therapies to reduce perioperative morbidity and mortality are needed but remain elusive."

Efficacy and Safety of Pyridoxal 5'-Phosphate (MC-1) in High-Risk Patients Undergoing Coronary Artery Bypass Graft Surgery: The MEND-CABG II Randomized Clinical Trial
MEND-CABG II Investigators
JAMA (2008). 299[15]
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: Peter M Crosta

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