Mechanical prosthetic heart valves: Quality of anticoagulation and thromboembolic risk. The observational multicenter PLECTRUM study.

Background: Patients with a mechanical prosthetic heart valve implantation need to be treated with a vitamin K antagonist (VKA) due to a substantially high risk of thromboembolism. In this study we report data on patients with mechanical heart valves (MV), with the aim of evaluating the thromboembolic risk in relation to the type and site of implantation, quality of anticoagulation and risk factors associated with thromboembolism.

Methods: Observational retrospective multicenter study among Centers affiliated to the Italian Federation of Anticoagulation Clinics (FCSA) on patients with MV implanted after 1990 and followed for the management of anticoagulation.

Results: We analyzed 2357 patients with mechanical heart valves (55.2% males), followed for 24,081 years. During the follow-up, 164 thromboembolic events (0.67/100 pt-yrs) and 243 major bleedings (1.0/100 pt-yrs) occurred. The median Time in Therapeutic Range (TTR), calculated in all intended INR classes, was 60% (IQR 47-74%). The rates of thrombotic events were significantly higher in patients intended to stay at therapeutic ranges >INR 2.0-3.0. The presence of atrial fibrillation, history of thromboembolism and of mitral prosthesis were independently associated with thromboembolism. However, a bad quality of anticoagulation (TTR <47%, 25°percentile of our population) was not correlated with thromboembolism.

Conclusions: A low rate of bleeding and thromboembolic events in patients with mechanical heart valves were found, despite the sub-optimal anticoagulation control. The thromboembolic risk was not associated with the low TTR.