Mechanical heart valve prosthesis and warfarin - treatment quality and prognosis

Every year about 2500 patients in Sweden undergo surgery due to heart valve disease. A mechanical heart valve prosthesis causes risk of thromboembolic stroke or thrombus formation in the valve while anticoagulant treatment increases the risk of bleeding. Treatment quality with warfarin is crucial for patients with mechanical valve prostheses. It has previously been shown that poorly controlled warfarin treatment increases mortality in this patient group. TTR (Time in Therapeutic Range) on warfarin has been shown to affect the risk of complications in atrial fibrillation, but has not been studied in patients with mechanical heart valves. Our aim is to evaluate the impact of TTR on the risk of complications in this patient group.

A non-randomized, prospective study of 534 adults with mechanical heart valve prostheses from Malmö and Sundsvall registered in the Swedish National Quality Registry Auricula between 01.01.2008 and 31.12.2011. Quartiles regarding individual TTR levels were compared regarding risk of complications.

The risk of complications was significantly higher at lower TTR levels for all complications (p=0.005), bleeding (p=0.01) and death (p=0.018) but not for thromboembolism. In multivariate analysis the risk was significantly increased at lower TTR levels for bleeding and all complications but not for death or thromboembolism.

Patients with a lower warfarin treatment quality measured by TTR have a higher risk of complications such as severe bleeding or death. A TTR of 83% or higher at the individual level should be obtained for best outcome.