Anticoagulation protocol and early prosthetic valve thrombosis.

BACKGROUND: [corrected] Prosthetic valve thrombosis is a major cause of morbidity and mortality following heart valve replacement with a mechanical valve.

METHODS AND RESULTS: 538 patients who underwent mechanical valve replacement between April 1999 and June 2003 were included in the study. They were divided into two groups. Group A (n=245) consisted of patients who underwent mechanical valve replacement between April 1999 and June 2001. Anticoagulation was started on the first post-operative day and consisted of only oral nicoumalone. Group B (n=293) consisted of patients who underwent mechanical valve replacement between July 2001 and June 2003; enoxaparin was started six hours following surgery in addition to oral nicoumalone which was started on first post-operative day. Fifteen (6.1%) patients in group A developed early prosthetic valve thrombosis at an interval of 4.33+/-0.97 months (range 3-6 months) following surgery. Ten had prosthetic valve thrombosis in the mitral position and five had prosthetic valve thrombosis in the aortic position. In group B, six (2.1%) patients developed early prosthetic valve thrombosis at a median interval of 4.58+/-0.9 months (range 3.5-6 months) in the mitral position (p=0.01).

CONCLUSIONS: Addition of enoxaparin to the anticoagulation regime in the immediate post-operative period significantly reduces early prosthetic valve thrombosis.