Following reports of advanced imaging studies showing reduced leaflet motion with some bioprosthetic aortic valves, the FDA has announced it is working with American College of Cardiology, the Society of Thoracic Surgeons, and device manufacturers to design clinical studies to fully evaluate reduced leaflet motion for all types of bioprosthetic aortic valves. However, the agency says—at this time—it believes bioprosthetic aortic valves are reasonably safe and effective when used according to their FDA-approved indications.
The FDA reports, in a notification, that the agency is aware of recent reports regarding reduced leaflet motion in some bioprosthetic aortic valves, including those used in both surgery and in transcatheter aortic valve implantation (TAVI). It adds: “Importantly, 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.”
According to the FDA, the leaflet motion abnormalities were detected using 3D and 4D computed tomography scans or by transesophageal echocardiography. It says that “of note” transthoracic echocardiography—the routine imaging method used to assess valve function following implantation—did not reliably detect abnormal leaflet motion. The agency comments: “Most advanced imaging studies have been conducted in TAVI patients, and that might be why there have been more reports of reduced leaflet motion in TAVI patients as compared to surgical aortic valve replacement (SAVR) patients. The true rate of reduced leaflet motion for bioprosthetic aortic valves, whether TAVI or SAVR, is currently not known. In the limited available information that FDA has reviewed regarding advanced imaging studies of bioprosthetic aortic valves, reduced leaflet motion was seen in between 10% and 40% of TAVI patients and about 8–12% of SAVR patients.”
It adds that definitive cause(s) of reduced leaflet motion in some bioprosthetic aortic valves also is not known, noting that the evidence from imaging studies suggests that blood clot deposits on the leaflets may cause restricted motion. The prevalence of reduced leaflet motion was less in patients receiving therapeutic anticoagulation with warfarin compared with those receiving sub-therapeutic or no anticoagulation and with those receiving dual antiplatelet therapy.
However, the FDA says that “at this time” it believes that bioprosthetic aortic valves remain reasonably safe and effective when used according to their approved indications. “This view is supported by the favourable benefit/risk profile observed in SAVR devices in the 30 years they have been on the market and in TAVI devices in the eight years they have been in use. Implantation of these devices reduces symptoms, improves quality of life, and prolongs life for tens of thousands of patients each year. 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, treatment options should be discussed with the team of heart physicians responsible for the patient’s care,” the agency adds.
As a next step, to address the limited data for this issue, the FDA is working with ACC, the STS, and the device manufacturers to design clinical studies to fully evaluate reduced valve leaflet motion for all types of bioprosthetic aortic valves.