Serum Lactate Dehydrogenase Elevation

Activity of total lactate dehydrogenase (LDH) and that of the heat-stable isozyme (LDH-1) was measured by the method of Strandjord and Clayson in the serum of 62 cardiac patients with congenital and valvular heart disease before and after cardiac catheterization and at follow-up examination after cardiac surgery. A universal elevation of both total and heat-stable LDH was found in patients with prosthetic heart valves of several types. Lesser degrees of abnormalities were seen in a number of the patients without prosthetic devices. Some patients had a small increase in serum enzyme activity the day after cardiac catheterization. The evidence presented implicates hemolysis in the production of these abnormalities. It is suggested that all patients with prosthetic valves and a significant percentage of patients with severe hemodynamic abnormalities have chronic, usually compensated, intravascular hemolysis secondary to mechanical damage to red blood cells. These findings must be kept in mind in interpreting serum LDH determinations in patients with valvular prostheses