Erythrocyte survival in patients with porcine xenograft aortic and mitral valves

Time Does Not Heal All Ills: The Late Occurrence of Hemolytic Anemia After Prosthetic Mitral Valve Replacement

Hemolytic anemia is a well-known complication of prostheses following the replacement of cardiac valves. Therefore, in all patients with prosthetic valve placement who present with anemia or hyperbilirubinemia, hemolysis is an important differential that must be ruled out, irrespective of how long the valve replacement has lasted. Indications for repair either through percutaneous or surgical approach generally include the severity of hemolysis based on either persistent symptoms of fatigue, the continued requirement of blood transfusions, or else the progression of valvular dysfunction. However, if hemoglobin remains stable, symptoms resolve, there is minimal functional impairment, or the risk of comorbidities is greater than the benefits of invasive intervention, then an initial trial of medical therapy is prudent. Our case report is unique as it demonstrates the late occurrence of symptomatic severe hemolytic anemia more than 20 years after valvular replacement. It also offers an alternative approach to invasive management in patients who develop this complication after such a prolonged asymptomatic period. 

Morphologic diagnosis of thrombotic thrombocytopenic purpura

The diagnosis of thrombotic thrombocytopenic purpura (TTP) rests on evidence of microangiopathic hemolytic anemia and thrombocytopenia in the absence of disseminated intravascular coagulation and other known causes of thrombotic microangiopathy. Highly specific diagnostic tools such as serum levels of ADAMTS13 are not routinely available for immediate clinical diagnosis. The presence of schistocytes on a blood smear is the morphologic hallmark of the disease, but no guidelines exist as to the number of schistocytes required to differentiate TTP from other thrombotic microangiopathies. We studied 6 patients with TTP and compared their schistocyte counts with those of 40 normal subjects, 28 patients with chronic renal disease, 5 with preeclampsia, and 5 with normal functioning mechanical heart valves. The mean schistocyte count for the TTP patients was 8.35% versus 0.05% for normal subjects, 0.2% for renal patients, 0.25% for preeclamptic patients, and 0.18% for patients with mechanical valves (P < 0.001). Schistocytes were found on 100% of blood films of TTP patients and ranged from 1.0% to 18.4% of red cells. Schistocytes are found on the smears of 58% of normal individuals and on 80-100% of the other patient groups studied, but always comprise less than 0.5% of the red cell population. An initial schistocyte count of greater than 1% strongly suggests a diagnosis of TTP in the absence of other known causes of thrombotic microangiopathy.

Hemolytic anemia secondary to a porcine mitral prosthetic valve leaflet dissection

This is a case of a dissecting cusp of a mitral porcine xenograft causing severe hemolytic anemia in the absence of valvular dysfunction and regurgitation. Six months after valve replacement, the patient had no evidence of hemolytic anemia. A cuspal dissection between the atrial and ventricular membranes was found on histologic evaluation.

Mechanical trauma to red blood cells caused by Björk-Shiley and Carpentier-Edwards heart valves

The haemolytic properties of mechanical and biologic valve prostheses are well established, and it is known that they can shorten red cell survival time (1, 2). Their effects on red cell deformability are not known, however. A comparative study was therefore made of two valve types--Björk-Shiley (BS) and Carpentier-Edwards (CE). Thirty-nine patients with normally functioning valve prostheses (23 BS, 16 CE) were studied at least one year after surgery, by assessing red cell deformability measured as red cell filtration rate (RFR), red cell survival half-time with the Cr-51 isotope method (Cr-51 T1/2) and plasma-haemoglobin (P-Hb). The BS valve was shown to be more traumatic to the cells than the CE valve and effected greater reduction of the deformability of these cells. Significant intercorrelations were found between RFR, CR-51 T1/2 and P-Hb.

Improved red cell survival in patients with chronic subclinical haemolysis due to artificial heart valve. Observations after in vitro treatment of the cells with potassium cyanate

Red cell survival was studied with use of Chromium-51 isotope and standard haematologic tests of haemolysis. The study comprised 30 patients with normally functioning single artificial heart valves of various types. They were investigated on 2 or 3 occasions. Red cells labelled with Cr-51 were treated for 30 min with potassium cyanate (0.5 mg/100 ml) in 5% invertose or with only 5% invertose. The mean red cell survival without cyanate treatment was 25 (+/- 4.2) days. Following cyanate treatment this figure improved to 31 (+/-4.8) days. Low-grade chronic intravascular haemolysis was associated with all the valve types. Abnormal results were found in 67% and 62% of the tests in patients with ball-type valve (deBakey and Starr-Edwards, respectively). The figures for tilting disc values (Lillehei-Kaster and Björk-Shiley) were 51 and 45.5%, while Carpentier-Edwards bioprosthetic valves gave 15.5% abnormal test results. The findings thus suggested that ball valves are more haemolytic than tilting disc valves, which in turn are more haemolytic than tissue valves.