Diagnostic value of D-dimer and antithrombin-III levels in predicting prosthetic heart valve thrombosis

The aim of this prospective study was to investigate the diagnostic value of plasma D-dimer levels and antithrombin-III activity in predicting prosthetic valve thrombus. The study group comprised 97 consecutive patients with prosthetic heart valves (59 with mitral, 21 with aortic, and 17 with both mitral and aortic prostheses) and 35 healthy control subjects. Six patients presented with symptoms of obstruction; the remaining 91 were asymptomatic. Patients were evaluated by both transthoracic and transesophageal echocardiography. Asymptomatic nonobstructive thrombus was detected in 13 patients (13%), whereas obstructive thrombus was demonstrated in all symptomatic patients. Plasma antithrombin-III levels of patients with prosthetic valve thrombi were slightly lower than those of patients without thrombus and of the control group, but the difference was not statistically significant. However, significantly higher plasma D-dimer levels were observed in patients with prosthetic valve thrombi, compared with patients without thrombus and the control group (735 +/- 633 microg/L, 372 +/- 342 microg/L, and 228 +/- 219 microg/L, respectively). Valve thrombus, the prosthetic heart valve itself, and INR levels were identified as major determinants of plasma D-dimer levels. A plasma D-dimer level of >445 microg/L predicted the presence of a prosthetic valve thrombus with 57.8% sensitivity and 83.3% specificity (positive predictive value, 47.8%; negative predictive value, 87.8%). Current data suggest that increased plasma D-dimer levels can be clinically helpful in predicting the presence of prosthetic valve thrombus. Plasma antithrombin-III activity does not seem to have a diagnostic value in predicting prosthetic valve thrombi.