Intravascular haemolysis and thrombocytopenia in left ventricular outflow obstruction'

Abstract

Twenty-four patients with various types of isolated discrete aortic stenosis of a wide range of severity or with muscular obstruction to left ventricular outflow were studied haematologically and by cardiac catheterization and angiocardiography. Patients had haematocrits, reticulocyte, platelet, and megathrombocyte counts, serum haptoglobin, and lactic dehydrogenase performed; urine specimens were examined for haemosiderin and peripheral blood smears examinedfor schistocytes. Seventeen patients had 51chromium red blood cell survival tests and 7 patients had plasma heme pigment determinations. In discrete aortic stenosis (supravalvular, valvular, or subvalvular), intravascular haemolysis developed when pressure gradients of 50 mmHg or more were achieved. Gradients of this magnitude caused damaging shear stresses of at least 4000 dynes/cm2 on red blood cells. Intravascular haemolysis was also found in 2 patients with functionally normal bicuspid aortic valves. In idiopathic hypertrophic subaortic stenosis, intravascular haemolysis was found in 4 of 7 patients and appeared to be related to the presence of a left ventricular-aortic systolic gradient and/or the rapid rate of ejection. Of the 24 patients, io had an increased megathrombocyte count; 5 of these had thrombocytopenia. Four patients with thrombocytopenia also had intravascular haemolysis, but there was no clear correlation between increased peripheral destruction ofplatelets and the haemodynamic findings.