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.