Use of prothrombin fragment 1+2 for evaluating anticoagulant therapy after mechanical heart valve replacement

Abstract

Prothrombin fragment 1+2 (F1+2) is a coagulation factor newly used as a molecular marker to monitor anticoagulant therapy in patients undergoing heart valve replacement. We evaluated the usefulness of F1+2 against that of prothrombin time (PT) reported as the internationalized normalized ratio (INR) in 93 patients undergoing mechanical heart valve implantation between August 1999 and July 2000. The study group consisted of 38 men and 55 women, with an average age of 61.1±11.2 years. The surgeries were 34 aortic replacements, 9 double valve replacements, and 50 mitral valve replacements. Warfarin doses were controlled based on PT-INR values at a target range of 1.5–2.5 F1+2 levels in the 0.4–1.2 nmol/l level were considered normal. No thromboembolism or bleeding complication occurred in any patient during the mean follow-up period of 12 months. The overall correction coefficient between F1+2 and PT-INR was 0.165 (P<0.001). A few specimens showed abnormally high levels of F1+2, even when PT-INR values were within the optimal range. The plasma levels of F1+2 that fell within normal range came from specimens with PT-INR values <1.50. The plasma levels of F1+2 that corresponded to PT-INR values of 1.50–2.50 fell just within the normal range, and the F1+2 levels corresponding to PT-INR values >2.50 were less than half of the lower limit of normal. Our analysis involving F1+2 confirmed PT-INR in the 1.5–2.5 range following mechanical heart valve implantation to be optimal. We found that using F1+2 to monitor individual response to anticoagulation therapy is useful when PT-INR values are difficult to obtain.