Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + INTRODUCTION Download Section PDF Listen +++ +++ Definition ++ Also referred to as macroangiopathic hemolytic anemia, a type of fragmentation hemolytic anemia. Complications of prosthetic heart valves (or less commonly cardiac valve disorders, especially severe aortic or subaortic stenosis) or other mechanical cardiac devices, such as left ventricular assistance devices. Turbulence and high shear stresses within a space enclosed by a foreign surface result in red cell fragmentation and hemolysis. +++ Clinical Features ++ Patients with ball-and cage valves, bileaflet valves (as compared to tilting disc valves), mechanical valve prostheses versus xenograft tissue prostheses, and double-valve as compared to single-valve replacement are more likely to experience clinically significant hemolysis. Hemolytic anemia is usually mild and compensated but may be severe. Coexistent other causes of anemia (iron or folate deficiencies, see Chaps. 8 and 9), and increased cardiac output as a consequence of strenuous physical exertion, can convert mild hemolysis without anemia to moderate or severe hemolysis and a more severe anemia resulting from increased shear stress. More important clinically is the thrombogenicity of nonendothelialized surfaces, as well as the loss of nitric oxide-mediated reduction in platelet reactivity and vasodilation, which promote platelet thrombosis and embolization (see Chapter 19). +++ Laboratory Features ++ Blood film: moderate poikilocytosis, schistocytosis, and polychromasia may be present (see Table 20–1). Serum levels of total and indirect bilirubin, and LDH can be elevated, whereas the serum haptoglobin is depressed. Urine hemosiderin present as a result of intravascular hemolysis. Iron deficiency may result from chronic hemoglobinuria and hemoglobinuria. Decreased platelet count may indicate platelet thrombi on valve surfaces. ++Table Graphic Jump LocationTABLE 20–1SEVERITY OF PROSTHETIC VALVE HEMOLYSISView Table||Download (.pdf) TABLE 20–1 SEVERITY OF PROSTHETIC VALVE HEMOLYSIS Mild Moderate Severe Hemosiderinuria Present Present Marked Hemoglobinuria Absent Absent Absent Schistocytosis < 1% > 1% > 1% Reticulocytosis < 5% > 5% > 5% Haptoglobin Decreased Absent Absent LDH < 500 Units/L > 500 Units/L > 500 Units/L LDH, lactic acid dehydrogenase.Source: Williams Hematology, 8th ed, Chap. 50, Table 50–2, p. 759. +++ Diagnosis ++ Based on the presence of schistocytes on the blood film and evidence of chronic intravascular hemolysis in a patient with a cardiac valve disorder or an artificial heart valve or cardiac device. +++ Treatment ++ Appropriate therapy is to replace iron and folate (if deficient). Surgical repair or replacement of the malfunctioning prosthesis (if indicated). Transfusion may be necessary preoperatively and may diminish the rate of hemolysis by decreasing the heart rate and flow velocity. For severe anemia ineligible for reoperation, recombinant human erythropoietin treatment may diminish or eliminate transfusion requirements. + MARCH HEMOGLOBINURIA AND SPORTS ANEMIA Download Section PDF Listen +++ +++ Definition ++ First described in a German soldier in whom hemoglobinuria was brought on by marching. Also seen in young athletes with frequent participation in severe and prolonged exertion. Hemoglobinuria has also been seen following other types of trauma in activities as diverse as repetitive slapping of the forehead, karate exercises, congo drum playing. +++ Clinical and Laboratory Features ++ Because the estimated quantity of blood hemolyzed in an average paroxysm is only 6 to 40 mL, anemia is uncommon; however, repeated episodes may eventually lead to iron deficiency (see Chap. 9). Reticulocyte count may be mildly increased, especially in active runners. Serum iron, ferritin, and haptoglobin concentrations are usually decreased. Hemoglobinuria may be noted for 6 to 12 hours in runners after a race and hemosiderinuria for several weeks after an acute episode. +++ Diagnosis ++ Hemoglobinuria follows exercise or physical insult. The Donath-Landsteiner test for paroxysmal cold hemoglobinuria and a test for paroxysmal nocturia hemoglobinuria may be performed to rule out these causes of hemoglobinuria. Myoglobinuria can be distinguished from hemoglobinuria by chemical tests of urine. Athletes with occult blood in stools should be tested for an underlying gastrointestinal tract abnormality, despite the frequency of subclinical gastrointestinal bleeding after strenuous exercise. Anemia also occurs in astronauts but it is not related to shear stress in erythrocytes (see Chap. 2). +++ Therapy ++ For march hemoglobinuria, reassure the patient, add cushioned insoles to the shoes, and suggest that changing the gait may ameliorate the condition. Correct iron or folate deficiency, if present. ++ For a more detailed discussion, see Kelty R. Baker and Joel Moake: Hemolytic Anemia Resulting from Physical Injury to Red Cells. Chap. 50, p. 755 in Williams Hematology, 8th ed.