Antithrombotic therapy
With either type of prosthesis or valve location, the risk of emboli is probably higher in the first few days and months after valve instertion, before the valve is fully endothelialized.
Patients with a mechanical prosthetic heart valves have a 2-4% per year risk of embolism. Rates are higher for mitral than aortic valves, and in patients with atrial fibrillation.
- Mechanical valves
- all patients with mechanical valves required individualised anticoagulation with consideration of risk factor for thromboembolism. The addtion of aspirin 75 mg per day to warfarin should be strongly considered unless there is a contraindication to the use of aspirin (ie peptic ulceration, bleeding or apsirin intolerance) as this further decreases the riskof thromboembolism and mortality due to other cardiovascular diseases
- Biological valves
- for patients with biological valves, a variety of different antithrombotic regimes have been published and practice varies widely between UK cardiac surgical units. Aspirin 75 mg per day should be used in all patients unless contraindicated
- after 3 months tissue valves can be treated like native valves and warfarin can be discontinued in more than 2/3 of patients with biological valves. In the remaining patients with associated risk factors for thromboembolism, such as atrial fibrillation, previous thromboembolism, or hypercoagulalable conditions, lifelong warfarin therapy is indicated. Many would also recommend continuing anticoagulation in patients with severe left ventricular dysfunction (ejection fraction less than 30%)
Reference:
- 1) BHF (factfile May 2009). Prosthetic heart valves.