Platelet Survival Using Aspirin: Studies in Patients with Artificial Cardiac Valves

Abstract

Studies using 51Cr-labeled platelets have shown reduced platelet survival in patients with artificial cardiac ball valves. Recently, a simple non-radioisotopic method for measuring platelet survival has been developed by Stuart (NEJM 292:1310, 1975) based on the concept that aspirin (ASA) irreversibly inhibits lipid peroxidation of circulating platelets. This method was used to determine platelet survival in 20 control subjects, 8 patients with normally functioning Starr-Edwards artificial cardiac valves (cardiac catheterization 5/8) and 4 patients with documented prosthetic valve dysfunction. The T½ (best fit to an exponential curve) for control subjects was 4.0 ± 0.7 (1 SD) days with a range of 3.0 to 5.6 days. The T½ of normally functioning artificial valves was less than that of the control subjects (3.3 ± 0.3 days, range 3.1 – 3.8 days, p < 0.05). Moreover, the patients with valves that were obstructed or had a peri prosthetic leak had a T½ of 2.7 ± 0.1 days, which was significantly shorter than either the controls or the patients with normally functioning artificial valves (p < 0.01). Two additional valve patients also showed shortened platelet survival (subacute bacterial endocarditis – T½ 2.9 days, acute intimai tear of the aorta – T½ 2.5 days) and 2 patients without prostheses who were taking dipyridamole had normal platelet survival [T½ 4.0, 3.3 days). These results indicate that the ASA method for determining platelet survival identifies shortened platelet survival in patients with artificial cardiac valves and may be a useful non-invasive tool to detect prosthetic valve dysfunction.