Abstract 12254: The QRS Frontal Plane Axis Changes During Left Bundle Branch Block After Transcatheter Aortic Valve Replacement

Abstract

Background: Left bundle branch block (LBBB) is common after transcatheter aortic valve replacement (TAVR) and associated with either a left or normal frontal QRS axis. Research Questions: To assess the QRS frontal plane axis shift changes during LBBB after TAVR and determine if the risk of procedure-related high degree atrioventricular block (AVB) is affected by these QRS axis shift changes. Methods: In a retrospective single-center study of 720 consecutive patients who underwent TAVR, 141 (19.6%) with normal baseline QRS duration developed a new LBBB after TAVR and constituted the study group. Most patients (59.6%) were females, and the mean age of the cohort was 81.2±6 years. About two-thirds of the patients were implanted with a self-expandable valve. The length of hospital stay was 6.6±4.4 days. Results: This study show 3 main findings: 1) As compared with the baseline QRS axis before TAVR, the occurrence of LBBB after TAVR was associated with a leftward QRS axis shift (by 40+28.3°) in 73% of the study patients and a rightward (by 18.6+19.4°) or no change in QRS axis in 25.6% and 1.4% of the study patients, respectively. These results were not affected by the type and size of prosthetic valve used. 2) Although the proportion of patients having a left QRS axis (<-30°) markedly increased after TAVR in the study group (from 14.9% to 38.3%) and in the group displaying a leftward QRS axis shift (from 5.8% to 45.6%), converse results were observed in the group displaying a rightward QRS axis shift (decrease from 38.9% to 16.7%). 3) The group of patients exhibiting a rightward or no QRS axis shift tended to show a greater incidence of high degree AVB than the group of patients exhibiting a leftward QRS axis shift (18.4% vs. 6.8%, P=0.056). Conclusion: Although post TAVR-LBBB was associated with a leftward QRS axis shift in most patients (73%), a non-negligible proportion of patients (27%) exhibited a rightward or no QRS axis shift. The latter group tended to have a higher risk of developing high degree AVB.