Bioprosthetic aortic valves play a critically important role in improving the health and quality of life of many patients with severe aortic valve disease. Recently, advanced imaging studies detected reduced leaflet motion (i.e., impaired valve opening) in some bioprosthetic aortic valves. The cause and occurrence rate of reduced leaflet motion is currently not known. Likewise, whether or not this finding has clinical implications for patients and patient care is also not known. 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 leaflet motion for all types of bioprosthetic aortic valves. At this time, FDA believes that these devices are reasonably safe and effective when used according to their FDA-approved indications.
The aortic valve is located between the main pumping chamber of the heart (left ventricle) and the major artery that carries blood from the heart to the rest of the body (aorta). When this valve is diseased, the opening can narrow, restricting blood flow (stenosis), or the valve can fail to close properly, allowing blood to flow backward into the heart (regurgitation).
In many patients, diseased aortic valves are replaced with bioprosthetic valves (valves made from animal tissues, with or without additional support structures). The three leaflets of a bioprosthetic aortic valve open and close like doors to allow blood to flow forward and to prevent backward flow. Bioprosthetic aortic valves can be categorized into two general types: those for surgical aortic valve replacement (SAVR, performed via open-heart surgery) and those for transcatheter aortic valve replacement (TAVR, performed without open-heart surgery).
The FDA is aware of recent reports regarding reduced leaflet motion in some bioprosthetic aortic valves, including both SAVR and TAVR devices. 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.
The leaflet motion abnormalities were detected using special 3- and 4-dimensional computed tomography (3D and 4D CT) scans or by transesophageal echocardiography (TEE). Of note, transthoracic echocardiography (TTE), which is the routine imaging method used to assess valve function following implantation, did not reliably detect abnormal leaflet motion.
Most advanced imaging studies have been conducted in TAVR patients, and that might be why there have been more reports of reduced leaflet motion in TAVR patients as compared to SAVR patients. The true rate of reduced leaflet motion for bioprosthetic aortic valves, whether TAVR 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 10-40% of TAVR patients and about 8-12% of SAVR patients.
The definitive cause(s) of reduced leaflet motion in some bioprosthetic aortic valves also 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 receiving therapeutic anticoagulation with warfarin compared with those receiving sub-therapeutic or no anticoagulation and with those receiving dual anti-platelet therapy.
In one study, treatment with blood thinning medications (anticoagulants) resulted in the resolution of the leaflet motion abnormalities.
FDA’s Current Perspective
At this time, 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 8 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.
These reports have raised important questions about bioprosthetic aortic valves. However, limited available data do not allow us 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.
Reporting to FDA
Prompt reporting of adverse events can help the FDA identify and better understand the risks associated with bioprosthetic aortic valves. If you suspect or experience a problem with a bioprosthetic aortic valve, we encourage you to file a voluntary report through MedWatch, the FDA Safety Information and Adverse Event Reporting program. Health care personnel employed by facilities that are subject to FDA's user facility reporting requirements should follow the reporting procedures established by their facilities.
The reported phenomenon of reduced leaflet motion seen in bioprosthetic aortic valves is an early signal with unknown clinical significance. The FDA continues to closely monitor this signal and is working with the clinical community and device manufacturers to design studies to help us better understand the mechanism, incidence, risks, and consequences of reduced leaflet motion. This research also will help us determine whether there is a need for treatment and, if so, guide the appropriate treatment strategies. We will issue additional comments to the public when more information becomes available.