Introduction
Transcatheter aortic valve replacement (TAVR) has been established as a treatment of symptomatic aortic stenosis (AS) (1, 2 ), and its benefit has been extended to low-surgical risk patients (3, 4 ). Bicuspid aortic valve (BAV) is estimated to have a prevalence of around 0.5% (5 ) and 0.8% in the male population (6 ) and is associated with the risk of developing aortic stenosis due to underlying abnormal valve geometry and mechanical stress (7 ). Although AS patients with BAV were excluded from early pivotal randomized studies (1 - 4 ), the evidence concerning TAVR for BAV is important because of the high prevalence of BAV among younger AS patients. Recent studies have reported comparable prognosis, hemodynamic results, and the safety of TAVR for BAV stenosis as compared to tricuspid aortic valve (TAV) stenosis (8 - 10 ). In addition, a randomized study showed the safety of TAVR for BAV in comparison with surgical aortic valve replacement (SAVR) (11 ).
Conduction disturbance (CD) including new permanent pacemaker implantation (PPI) and complete left bundle branch block (LBBB) have been reported as major complications following TAVR, and they are also associated with the risk of increased mortality and hospital readmissions (12 - 14 ). To avoid TAVR-related CD, several techniques such as double-cusp-view implantation with self-expandable THV (15 ) and high implantation technique with balloon-expandable THV (16 ) have been proposed. In addition, membranous septum (MS) length represents an anatomic surrogate of the distance between the aortic annulus and the bundle of HIS, and MS length is inversely related to the risk of CD following TAVR (17 ). Moreover, other studies reported, that both MS length and implantation depth are associated with CD (18, 19 ). However, less is known about the impact of the implantation depth and the MS length on CD outcomes in bicuspid anatomy
This study aimed to investigate the impact of MS length and implantation depth in predicting CD following TAVR with balloon-expandable valve in patients with BAV.