Transcatheter aortic valve replacement in bicuspid aortic valve stenosis: where do we stand?

Bicuspid aortic valve is the most common congenital cardiac defect in adults, and symptom typically develops in adulthood. In the majority of cases, bicuspid aortic valve disease progress with ages and surgical aortic valve replacement is performed with excellent operative outcomes. However, with the relatively slow progression of disease, surgical aortic valve replacement is required in elderly patients but the surgical risk often deemed extremely high due to old age and multiple comorbidities. Transcatheter aortic valve replacement (TAVR) has evolved from a novel technology to an established therapy for intermediate-and high-risk patients with symptomatic severe aortic valve stenosis (AS). Numerous studies have demonstrated the safety and efficacy of TAVR, and more than 250,000 patients have been treated with this technology. Although randomized trials have established TAVR as the standard treatment, these trials excluded congenital bicuspid AS due to its unique morphological features. Nevertheless, the growing experience, accumulated knowledge, and advancements of new technology lead to the expand use of TAVR to other pathologies or other populations such as bicuspid AS. With integration of imaging multimodalities (computed tomography and echocardiography), the diagnosis and classification of bicuspid aortic valve has been changing. Due to unfavorable anatomic features of bicuspid AS, the outcomes of TAVR in bicuspid AS was suboptimal, particularly when using the first-generation transcatheter valves. However, the newer-generation transcatheter valves significantly improved the outcomes of TAVR in bicuspid AS. Nonetheless, several issues still remain to be resolved. Given longer life expectancy in patients with bicuspid AS undergoing TAVR, durability of transcatheter valves is concerned. In addition, patients with bicuspid aortic valves often have concomitant dilatation of proximal part of ascending aorta (aortopathy), but limited data exist about the clinical prognosis of bicuspid aortic valve with concomitant aortopathy in elderly patients. Considering the expanding indication of TAVR to lower surgical risk and younger population, these issues should be evaluated in future studies.