Myocardial Response to Pretreatment with L-Carnitine in Patients with Cardiac Valve Replacement

Abstract

Twenty-one patients undergoing mitral valve replacement (MVR) with either isolated or combined valvular procedure were investigated to determine the ef fect of randomized and prospective administration of L-carnitine (car) chloride on myocardial function. Carnitine chloride (1800 mg/day, for seven consecu tive days just prior to MVR) was given orally to 9 patients (car-treated group) who were compared with 12 car-untreated patients (control group) subjected to the same procedure. Valve replacement was performed using the Bjork-Shiley mechanical prosthesis in aortic and mitral position and bioprosthesis in tricuspid position in both groups under cardiopulmonary bypass (CPB) associated with cold potassium-magnesium cardioplegia and systemic hypothermia. Preopera tive and intraoperative clinical profile (age, functional class, duration of aortic clamp and CPB, and level of hypothermia) was well matched in both groups. Free, short-chain acyl, long-chain acyl, and total Car were measured in the papil lary muscle excised adjacent to the free wall of the left ventricle at the time of valvular surgery. Heart rate and mean arterial pressure did not differ between the two groups. Cardiac index was 3.44 ± 0.08 and 3.82 ± 0.13 L/m2/min in the control and car-treated groups, respectively, (p < 0.05). Dobutamine (DOB) infusion rate was 8.55 ± 0.73 and 5.57 ± 0.95 μg/kg/min in the control and car-treated groups, respectively (p < 0.05). Left ventricular stroke work index (LVSWI)/DOB ratio was 4.50 ± 0.65 and 8.16 ± 1.72 g*m/m 2/beat/unit of DOB, in the control and car-treated groups, respectively (p < 0.05). Long-chain acyl carnitine was 0.224 ± 0.031 and 0.460 ± 0.096 nmoL/mg noncollagenous protein in the control and the car-treated groups, respectively (p<0.05). LVSWI/DOB ratio was well correlated with long-chain acyl carnitine in the tis sue, r = 0.74, n = 18, p<0.001. These findings suggest that pretreatment with L-carnitine chloride appears to be effective in improving myocardial function in the early phase of reperfu sion following surgery and that long-chain acyl carnitine may play a key role in the enhancement of carnitine-meditated mitochondrial metabolic process.