Background: Increase in hemolysis in the presence of paraprosthetic regurgitation has been stated in many studies. Total lactate dehydrogenase (LDH) showing hemolysis has been considered to be an important parameter in diagnosis. The aim of this study was to identify the possible role of the myocardial necrosis of left atrial free wall in the rise of LDH levels in patients with paraprosthetic regurgitation of mitral mechanical valves. Methods: We matched 15 patients (7 male, 8 female, mean age 44 ± 14 years) (Study group) who had mitral mechanical valve with severe paraprosthetic regurgitation to 15 patients (6 male, 9 female, mean age 35 ± 10 years) (Control group) who had native mitral valve with severe rhlumatical mitral regurgitation. On transesophageal echocardiographic examination, semiquantitative evaluation and spatial distrubution of regurgitant jets were noted in both of the groups. Five lactate dehydrogenase isoenzymes seperated by routine electrophoresis (cellulose acetate) were examine in two groups. Myocardial tissue specimens taken from the left atrial free wall were fixed in 2.5% phosphate buffered gluteraldehyde solution. Randomly taken grids from left atrial free wall were observed at the transmission electron microscope.
Results: Total serum LDH level of the study group (571 ± 8 IU/L) was higher than the control group (490 ± 61 IU/L) (p < 0.001). In two groups, we found LDH1/LDH2 > 1 in all patients. Electronmicroscopy showed the same necrotic changes in two groups.
Conclusions: Elevation in total LDH levels, high LDH1/LDH2 ratio and electronmicroscopic findings in all patients support that myocardial necrosis increases total LDH level. But statistically significant elevation in total LDH in the study group supports that hemolysis causing by paraprosthetic regurgitation is the most important factor for this increasing so that high LDH level can be used safely for the diagnosis of hemolysis in paraprosthetic regurgitation independent of the peresence of myocardial necrosis.

Keywords : Mitral, paraprosthetic regurgitation, myocardial necrosis, LDH, electronmicroscopy