Background: Conduction abnormalities, especially left bundle branch block (LBBB), frequently complicate transcatheter aortic valve replacement (TAVR). Acute effects of altered conduction on ventricular mechanics after TAVR have not previously been described.
Purpose: We aimed to investigate how TAVR procedure related conduction abnormalities influence ventricular mechanics with particular focus on new-onset persistent LBBB.
Methods: Patients with severe aortic stenosis undergoing transfemoral TAVR were included in a repeated measures cross-sectional study. ECG and echocardiography with speckle tracking strain analysis were performed before and after the procedure. LBBB was defined by strict ECG criteria. Mechanical contraction patterns were assessed by longitudinal strain in apical 4-chamber view and classified as classical, dyssynchronous LBBB contraction pattern (Figure, left panel) or non-classical patterns.
Results: We included 140 consecutive patients undergoing TAVR (83±8 years old, 49% women) with severe AS (valve area 0.7±0.2 cm2, mean pressure gradient 54±18 mmHg, peak velocity 4.5±0.7 m/s) and relatively preserved LVEF (52±11%). Compared to baseline, GLS improved after TAVR in all patients (-15.1±4.3 vs -16.1±3.9%, p<0.01, n=140), and all subgroups, regardless of, pre-existing (n=27) or procedure-acquired conduction abnormalities (n=32), including in the 28 patients with new-onset LBBB fulfilling strict ECG criteria (-14.5±3.9% vs -15.6±3.0%, p=0.03). Despite significant conduction delay in ECG, the vast majority of new-onset LBBB patients (n=26, 93%) had a non-classical homogenous contraction pattern with segmental synchronous peak shortening timed at aortic valve closure (AVC) and relatively sparse lateral wall pre-stretch (Figure, right panel). Classical dyssynchronous LBBB contraction pattern was only observed in 2 patients (7%) with new-onset LBBB.
Conclusions: Longitudinal function improved in all patients after TAVR, irrespective of conduction abnormalities. Classical dyssynchronous LBBB contraction pattern was absent in the majority of patients with new-onset post-TAVR LBBB, even when applying strict ECG criteria for LBBB. These findings raise a question of whether TAVR-induced LBBB may be functionally and prognostically different from traditional LBBB.