Intravascular stents do not cause microangiopathic hemolysis or thrombotic microangiopathy

An increased incidence of TTP has been noted among patients receiving intravascular stents to improve patency in diseased coronary, renal, and peripheral arteries. Placement of transjugular intrahepatic porto-systemic shunt stents is often associated with subsequent development of severe hemolysis. We have prospectively studied the development of microangiopathic hemolysis or TTP in patients undergoing intravascular stent placement for peripheral vascular or renal artery disease. Hemolysis was evaluated both before and after stent placement by measuring complete blood count, total bilirubin, lactate dehydrogenase (LDH), haptoglobin and reticulocyte count, and examining peripheral blood films of all patients. Coagulation parameters, blood urea nitrogen and creatinine were measured to exclude disseminated intravascular coagulation or thrombotic thrombocytopenic purpura as a potential cause of hemolysis. Seventeen patients (median age 69 years) were evaluated. One patient was on ticlopidine. Mean hematocrit fell from 41.8% pre-stenting to 35.5% post-stenting (P = 0.003) but without significant change in reticulocyte count (1.7 vs. 1.6%, P = 0.605), LDH (546 vs. 560 IU/l; P = 0.836), bilirubin (0.62 vs. 0.63 mg/dl; P = 1.0), or haptoglobin (183 vs. 158 mg/dl; P = 0.083). Thus, this drop in hematocrit could not be attributed to hemolysis. Peripheral blood films revealed fewer than 1% schistocytes before and after stent placement in all cases. Absence of significant changes in mean platelet count (240 vs. 210 x 10(9)/L; P = 0.088), fibrinogen (385 vs. 378 mg/dl; P = 0.789), BUN (24.5 vs. 16.8; P = 0.079), and creatinine (1.38 vs. 1.24; P = 0.757) argue against development of TTP or DIC resulting from stent placement. No patient developed new renal impairment, a neurological syndrome, or unexplained fever after stent placement. At a mean of 6 weeks follow-up after stent placement, patients have not developed signs of hemolytic anemia or worsening renal function. Our findings argue against a primary risk of microangiopathic hemolytic anemia or TTP due to intravascular stents in patients not receiving ticlopidine.