How does new-onset left bundle branch block affect the outcomes of transcatheter aortic valve repair?

INTRODUCTION: Transcatheter aortic replacement (TAVR) has revolutionized the treatment of aortic stenosis during the last years. Despite improvements in transcatheter heart valve systems, the rate of conduction disturbances after TAVR, particularly new-onset left bundle branch block (new-onset LBBB), has not decreased over time. AREAS COVERED: Overview of the current data regarding new-onset LBBB post-TAVR focusing on clinical outcomes. EXPERT OPINION: New-onset LBBB remains the most common complication after TAVR, occurring in 6-77% of cases with the use of newer generation transcatheter valve systems. The most consistent factor determining new-onset LBBB post-TAVR has been prosthesis implantation depth. The potential evolution to high degree atrioventricular block (HAVB) and the chronic effect on left ventricular ejection fraction (LVEF) may impact the clinical outcomes in this subset of patients. New-onset LBBB has been associated with an increased risk of PPM after TAVR. Conversely, inconsistent results have been reported regarding the impact of LBBB on hospitalization for heart failure and mortality. Current data do not support an indication for 'prophylactic' PPM in all new-onset LBBB patients. However, a specific subset of patients (those with either a very long PR or wide QRS) may benefit from a PPM to prevent HAVB or sudden death.