EFFECT OF L-CARNITINE ON MYOCARDIAL-METABOLISM - RESULTS OF A BALANCED, PLACEBO-CONTROLLED, DOUBLE-BLIND-STUDY IN PATIENTS UNDERGOING OPEN-HEART-SURGERY

The effects of L-carnitine on cardiac performance after open heart sur gery were evaluated in a balanced, placebo-controlled, double-blind st udy in 38 patients. Preoperative haemodynamic status was good in all o f them. Seventeen subjects underwent mitral valve replacement and 19 p atients coronary artery bypass grafting. Five grams L-carnitine were g iven intravenously over 2 h, twice daily for 5 consecutive days; moreo ver, 10 g L-carnitine in 1500 mi cardioplegia were administered throug h the aortic root after aortic cross-clamping. Surgery was always plan ned on treatment day 3. The post-ischaemic functional recovery of the heart was assessed by clinical parameters, as well as by biochemical a nd ultrastructure evaluations on biopsy specimens. No differences were found between the control and the treatment group with respect to all clinical parameters of cardiac performance after cardiopulmonary bypa ss. At anaesthesia induction, serum carnitine was significantly increa sed in treated patients, but carnitine concentrations in the right atr ial biopsy obtained just before aortic declamping were similar in the two groups. In patients with mitral valve replacement, L-carnitine the rapy was associated with significantly higher concentrations of pyruva te, ATP and creatine phosphate in papillary muscle. Glycogen levels we re also higher in the treated group, but the difference was not statis tically significant. Myocardial ultrastructure on septal biopsies, obt ained within 5 min from weaning from extracorporeal circulation, showe d better preservation scores for all considered parameters (nucleus, s arcoplasmic reticulum, mitochondria and cellular oedema) in the treate d subjects, although the difference reached statistical significance o nly for nuclei. When biochemical and ultrastructural data are consider ed, these findings suggest that L-carnitine improves myocardial metabo lism. However, it cannot be concluded that L-carnitine provides an adv antageous support therapy for well-compensated patients requiring card iac surgery. In contrast, the positive effects of L-carnitine on cardi ac recovery after bypass might become clinically relevant in the surgi cal setting for haemodynamically compromised patients, in which furthe r investigations are required. (C) 1998 The Italian Pharmacological So ciety.