Use of the amino acid supplement L-arginine after myocardial infarction does not improve cardiac function or measurements and may increase risk of death, according to an article in the January 4 issue of the Journal of the American Medical Association.
L-arginine is a widely available dietary supplement and is publicized as having benefits for patients with hypertension, angina, heart failure and sexual dysfunction, according to background information in the article. Prior studies suggest that L-arginine has the potential to reduce vascular stiffness.

Steven P. Schulman, MD, of Johns Hopkins Medical Institutions, Baltimore, and colleagues conducted the Vascular Interaction with Age in Myocardial Infarction (VINTAGE MI) clinical trial to test whether administering L-arginine to patients following a first ST-segment elevation myocardial infarction (STEMI) over a six-month period would decrease vascular stiffness and improve ejection fraction.

The randomized, double-blind, placebo-controlled trial included 153 STEMI patients; 77 were 60 years or older. Participants were enrolled from February 2002 to June 2004. Patients were randomly assigned to receive L-arginine (goal dose of 3 g three times a day) or matching placebo for six months.

The researchers wrote: "The VINTAGE MI study demonstrated that six months of L-arginine added to standard postinfarct medications did not reduce noninvasive measures of vascular stiffness, improve ejection fraction, or improve clinical outcomes. To the contrary, we noted a possible increased risk of death in older patients after infarction while taking L-arginine compared with those taking a placebo, leading to the early termination of the study. These findings have broad public health implications given the increasing availability and use of L-arginine in patients with and without established cardiovascular diseases."

Death occurred in 6 patients (8.6 percent) in the L-arginine group during the 6-month study period versus none in the placebo group.

"In conclusion, L-arginine therapy should not be given to patients following a myocardial infarction. It neither alters noninvasive measures of vascular stiffness nor improves left ventricular function. L-arginine therapy in older patients with diffuse atherosclerosis may worsen clinical outcomes," the authors wrote.