What is it about?
Glutamate is an amino acid that plays a key role in myocardial metabolism in association with ischemia. Glutamate has been shown to enhance recovery of metabolism and function of the heart in animal studies and a couple of small human studies. The uptake of glutamate by the heart after coronary surgery is increased but seems to be limited by the plasma levels of glutamate. Intravenous infusion increases plasma levels and myocardial uptake and may thereby facilitate recovery of metabolism and function of the heart after severe ischemia. In GLUTAMICS II, a randomized double-blind trial, we found that intravenous glutamate infusion reduced postoperative increase of a biomarker (NT-proBNP) for heart failure as well as the incidence of renal failure after coronary surgery, but only in patients without diabetes.
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Why is it important?
Coronary artery bypass surgery normally carries a low mortality, but it can be substantial in high-risk patients. When death occurs, it is usually caused by postoperative heart failure and its complications such as renal failure. Conventional treatment with inotropic drugs can be a double-edged sword. These drugs improve the circulatory state of the patient but at the expense of an increased myocardial oxygen demand, which can be harmful to the already ischemic heart. Facilitating natural recovery of the heart after ischemia with glutamate infusion may prevent heart failure and reduce the incidence of renal failure after coronary bypass surgery
Perspectives
In retrospect it was a mistake to include patients with diabetes, but the initial sample size calculation was based on a cohort including all patients. We did not anticipate that the proportion of patients with diabetes would double to 47%. The blunted effect in patients with diabetes agrees with previous observations and appears to be caused by downregulation of mitochondrial glutamate transporter EAAT1 in the diabetic heart. We suggest that the concept of enhancing natural recovery of the heart after ischemia with glutamate infusion merits further evaluation in patients without diabetes.
Rolf Svedjeholm
Linköping University
Read the Original
This page is a summary of: Effect of glutamate infusion on NT-proBNP after coronary artery bypass grafting in high-risk patients (GLUTAMICS II): A randomized controlled trial, PLoS Medicine, May 2022, PLOS,
DOI: 10.1371/journal.pmed.1003997.
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