At present, a bicuspid aortic valve is seen as a relative contradiction for transcatheter aortic valve implantation (TAVI) and, thus, surgical aortic valve replacement is the preferred approach in most of these patients. However, surgery is not always possible in some patients with bicuspid aortic valves (e.g. the risk of complications is too great) and, therefore, TAVI may be the only option. When faced with such a patient in a recent case, Danny Dvir (Interventional cardiologist, University of Washington Medical Center, Seattle) performed “tricuspidisation”— turning a bicuspid valve into a tricuspid valve—to ensure TAVI could be performed safely. He talks to Cardiovascular News about the challenge of bicuspid valves and why tricuspidisation may be a potential way of addressing this challenge in some patients.
What percentage of patients with aortic stenosis have bicuspid valves?
Bicuspid aortic valve is a relatively common congenital anomaly. It is estimated that approximately 1–2% of the general population have bicuspid aortic valves. In Asia, bicuspid aortic valves are especially common. People with bicuspid aortic valves are at increased risk for having aortic valve and aortopathies—these include aortic stenosis, regurgitation and dilation of the ascending aorta and aortic dissection. Epidemiologically, the younger the population of patients with aortic stenosis, the higher the rate of them having bicuspid aortic valves. Below the age of 65 years of age, almost half of patients, by several estimates, with aortic stenosis have bicuspid aortic valves.
How are aortic stenosis patients with bicuspid valves typically treated?
Patients with bicuspid aortic valves that have severe stenosis/regurgitation are conventionally treated with open heart surgery. These surgeries occasionally include replacement of the aorta, when it is dilated. Some of these patients are at increased risk for conventional surgery and are referred for TAVI. These procedures are occasionally more challenging.
Why is it challenging to use TAVI in these patients?
TAVI in bicuspid aortic valves is associated with inferior results. Unfortunately, these patients were excluded from the original large TAVI trials and, as a result, we do not have data comparing surgery and TAVI in bicuspid patients. However, large registries have suggested that TAVI in bicuspid aortic valves is associated with worse clinical outcomes. These registries mainly included patients treated with first generation devices but not always.
One of the challenges of aortic valve bicuspidity is that it represents a very heterogeneous group of anatomical pathologies. Patients with bicuspid valves not only have many different mechanisms of failure and aortic morphologies, but also their valve characteristics differ significantly by the existence of raphe, and by the amount and location of root calcification. It seems that TAVI is associated with inferior results especially in certain types of bicuspid aortic valves. In these conditions there is a higher risk of paravalvular leak, conduction defects, annular injury. Non-circular device expansion is more common in certain bicuspid TAVI procedures and this may lead to worse device durability.
Will this become more of an issue given that TAVI is increasingly being used in lower risk, younger patients?
Yes, indeed. As already mentioned, younger patients with aortic valve stenosis are much more likely to have bicuspid aortic valves. This is particularly the case in those younger than 70. Clearly, one of the main obstacles of expanding TAVI towards younger patients is our ability to treat patients with bicuspid aortic valves safely and effectively.