Short term administration of L-carnitine can be detrimental to the ischemic heart.

Previous studies have shown that L-carnitine (LC) supplementation may exert a cardioprotective effect in cardiomyopathy, prevent arrhythmias in myocardial infarction and increase exercise tolerance in angina. Interestingly, we demonstrated that short term preischemic administration of LC can be detrimental to ischemic heart. In isolated rat hearts treated with LC for 10 min before ischemia, a marked and concentration dependent arrhythmogenic activity were produced during both ischemia and reperfusion as increases in the number of ventricular ectopic beats, ventricular tachycardia and incidence of ventricular fibrillation. We hypothesized that preischemic using of LC for an inadequate time may pose arrhythmogenic activity, due to incomplete metabolism of fatty acids which in turn lead to production of toxic long chain fatty acid metabolites and also because of interruption in glucose oxidation.