Frequency and severity of intravascular hemolysis after left-sided cardiac valve replacement with Medtronic Hall and St. Jude Medical prostheses, and influence of prosthetic type, position, size and number.

Intravascular hemolysis occurs often in patients with mechanical heart valve prostheses, but in most cases is of mild degree and subclinical. The severity of hemolysis is reported to be related to the type, position and size of prostheses used, as well as the presence of valve malfunction. Hemolysis was evaluated in 170 patients with St. Jude Medical (SJM) and 80 patients with Medtronic Hall (MH) prostheses, with normal mechanical function. The presence and severity of hemolysis was assessed on the basis of serum lactic dehydrogenase, serum haptoglobin, blood hemoglobin and reticulocyte levels as well as the presence of schistocytes. Overall, patients with SJM prostheses had greater frequency (51.2 vs 18.7%, p < 0.005) and severity (p < 0.005) of hemolysis than patients with MH prostheses, irrespective of position and size. No patient had decompensated anemia. The frequency of hemolysis was similar in both groups with double-valve replacement, whereas severity was greater with SJM than MH prostheses (p < 0.001). The number and position of the prostheses were correlated with severity of hemolysis: Double-valve replacement and mitral position were correlated with greater hemolysis than single-valve replacement (p < 0.01) and aortic position (p < 0.01). Valve size, cardiac rhythm and time from operation did not correlate either with frequency or severity of hemolysis. It is concluded that in normally functioning SJM and MH prostheses: (1) hemolysis is frequent but never severe; (2) SJM demonstrates greater frequency and severity when compared with MH valve; and (3) number, position, but not size, significantly affect the severity of hemolysis.