In a safety alert issued on October 5, the Food and Drug Administration (FDA) noted recent reports of reduced leaflet motion in some bioprosthetic aortic valves, including both SAVR (surgical aortic valve replacement) and TAVR (transaortic valve replacement) devices.
Most cases of reduced leaflet motion were discovered by advanced imaging studies in patients without symptoms of abnormal bioprosthetic valve function. Further, these studies have shown that in valves with reduced motion of one or more individual leaflets, there was acceptable forward blood flow through the valve opening without evidence of stenosis (narrowing), according to the FDA.
The definitive cause(s) of reduced leaflet motion in some bioprosthetic aortic valves is not known. Evidence from imaging studies suggests that blood clot (thrombus) deposits on the leaflets may cause restricted motion. The prevalence of reduced leaflet motion was less in patients taking the anticoagulant warfarin compared with those receiving sub-therapeutic or no anticoagulant and with those receiving dual anti-platelet therapy.
In one study, blood thinning medications (anticoagulants) resolved the leaflet motion abnormalities.
The FDA believes that bioprosthetic aortic valves remain reasonably safe and effective when used according to their approved indications. This view is supported by the favorable benefit/risk profile observed in SAVR devices in the 30 years they have been on the market and in TAVR devices in the eight years they have been in use. Based on the currently available data “the FDA believes that the benefits of using these devices for the currently approved indications continue to outweigh the risks.”
Overall, six strokes occurred in studies reported in the New England Journal of Medicine but all occurred within 24 hours of implantation, suggesting that “these first-day strokes were related to the procedural aspects of TAVR rather than to leaflet thrombosis,” according to Medpage Today. The investigators acknowledged the possibility that patients receiving bioprosthetic valves may be at higher risk for “leaflet thrombosis and consequent embolic stroke than has previously been recognized.” In an editorial accompanying the article, Dr. David Holmes of the Mayo Clinic and Dr. Michael Mack of Baylor Scott and White Health in Plano, Texas, wrote that “given the rapid clinical adoption of TAVR” the new findings are “extremely important,” though “clear scientific answers are still lacking.”
The FDA said the reports have raised important questions about bioprosthetic aortic valves. But limited data do not allow FDA to fully characterize the causes, incidence, and short and long-term risks of reduced valve leaflet motion, or to recommend appropriate treatment. The FDA is working with the American College of Cardiology, the Society of Thoracic Surgeons, and the device manufacturers to design clinical studies to fully evaluate reduced valve leaflet motion for all types of bioprosthetic aortic valves.
For patients who have a bioprosthetic aortic valve, additional diagnostic imaging using 3D or 4D CT or TEE may be considered when clinically indicated. If reduced leaflet motion is found, the FDA advises that treatment options should be discussed with the team of heart physicians responsible for the patient’s care.