The Biological Heart Valve in Aortic Position and its Effect on the Brain

Abstract

Thromboembolic events are a major complication of valve replacement. Most of these occur in the brain, with devastating consequences. Biological heart valve prostheses have been designed to reduce these complications as much as possible. This has the advantage that they require less antithrombotic agents compared to mechanical valves. However, thromboembolic events still do occur. The main question is: are such devices thrombogenic on long-term? For this reason, only long-term results have been included. A literature review reveals that there are several sources of emboli: the diseased native valve itself as well as other cardiovascular conditions such as atrial fibrillation or poor left ventricular function. Annual rate of thromboembolism of different series have been compared as well as the effect of several antithrombotic regimens during the first three postoperative months, since this is the most hazardous period. The results of trans-catheter aortic valve implantation have also been added since this is a way to treat patients who cannot stand the trauma of valve surgery. High age and risk scores make comparison with valve surgery difficult however. In either case, the rate of thromboembolism is rather low. Anticoagulation is probably needed within the first three months. If additional risk factors are present, life-long anticoagulation becomes necessary. However, there are some serious limitations in this review. The most important are the lack of standardization of recording embolic events and the value of possible surrogate parameters such as brain lesions on magnetic resonance imaging and cognitive decline. Large scale randomized controlled trials to identify the best antithrombotic protocol are difficult to design: because of confounding patient-related risk factors, large patient number needed to detect significant differences, and large variations in possible combinations of agents. However, every effort should be made to register every event in an adequate and standardized way.