Nationwide Study Shows New-onset Left Bundle Branch Block After Transcatheter Aortic Valve Replacement Occurred in 15% of Intermediate Risk Patients and Is Associated with Worse 2 Year Outcomes

According to a new nationwide study,  new onset left bundle branch block (LBBB) post transcatheter aortic valve replacement (TAVR), a recently established therapy for intermediate risk surgical candidates with symptomatic, severe aortic stenosis, is associated with adverse long term clinical outcomes in patients without baseline conduction disturbances or pacemaker.  Based on the findings published in the European Heart Journal, these outcomes include cardiovascular mortality, re-hospitalization, new pacemaker implantation, and worsened left ventricular systolic function in intermediate risk patients.

In more recent medical practice, TAVR has increasingly been adopted as an alternative to surgical aortic valve replacement (SAVR) for intermediate and high risk surgical candidates with symptomatic, severe aortic stenosis (AS).  While the rates of some complications of TAVR have decreased over time with advancements in transcatheter heart valve (THV) technologies and operator experience, cardiac conduction disturbances have remained a frequent complication.  The clinical impact of new-onset LBBB after TAVR remains debatable. Previous clinical studies have shown association between new LBBB and all-cause and cardiovascular mortality, which has typically been attributed to progression to high-degree atrioventricular block (AVB), ventricular arrhythmia, or worsening cardiomyopathy.  However, many studies have failed to demonstrate an association between new LBBB and mortality.  Based on these obscurities this study hypothesized that new LBBB is associated with long term mortality and other adverse clinical outcomes in intermediate risk patients undergoing TAVR; the true impact of new LBBB after TAVR, which will likely become increasingly important as TAVR expands to lower risk patient populations with longer-term survival and fewer other drivers of mortality.

 

In this analysis, a total of 2043 intermediate risk patients underwent TAVR in the PARTNER II trial and the S3 intermediate risk registry, and survived to hospital discharge.  Exclusion criteria included baseline intraventricular conduction disturbance, permanent pacemaker (PPM) implanted before or during the initial hospitalization and missing or incomprehensive electrocardiogram (ECG) at discharge.  Amongst the total, 864 patients were excluded from the current analysis based on the previously listed criteria. Clinical data, ECGs, and transthoracic echocardiograms were obtained at baseline, hospital discharge, 30 days, 1 year, and 2 years.  Clinical outcomes at two years were compared between patients with and without persistent, new onset LBBB at hospital discharge, a variable analysis was performed to identify predictors of mortality. Of the 1179 intermediate risk patients, new onset LBBB at discharge occurred in 179 patients (15.2%).  No significant differences were identified between both groups in respect to echocardiographic variables and baseline ECG characteristics, except for higher rates of non-specific intraventricular conduction delay (IVCD) (QRS <120 ms) among patients with new LBBB. Thirty day all-cause and cardiovascular mortality rates as well as stroke, major vascular complications, and major bleeding rates were similar between patients with and without new LBBB.  In contrast, patients with new onset LBBB after TAVR had significantly higher 2 year rates of all-cause (19.3% vs. 10.8%, P = 0.002) and cardiovascular mortality (16.2% vs. 6.5%, P < 0.001).  New onset LBBB was also associated with worse left ventricular systolic function at 1 and 2 year follow-up.

Solidified clinical research has identified left bundle branch block as a well established risk factor for both cardiovascular and all-cause mortality in the general population and.in patients with diverse cardiovascular diseases.  This analysis from the PARTNER 2 trial and S3 intermediate risk registry is the first to investigate the clinical implications of new onset LBBB after TAVR specifically in intermediate risk patients.  As a retrospective analysis, this study naturally had limitations; these include the PARTNER II trial originally was not enforced to examine clinical outcomes associated with new onset LBBB after TAVR, existence of unmeasured confounding variables despite statistically significant outcomes, data regarding the causes of death were not available preventing further analysis for increased mortality, and a limited study population of patients with both new LBBB and new PPM.  In conclusion,  this large cohort of intermediate risk patients from the PARTNER II trial and registry resulted in  persistent, new-onset LBBB occurrence in 15.2% of patients without baseline conduction disturbances or pacemaker. Additionally, new onset LBBB was associated with adverse clinical outcomes at two years, including all-cause and cardiovascular mortality, rehospitalization, new pacemaker implantation, and worsened left ventricular systolic function.  In order to identify the optimal management strategy in patients with new LBBB post TAVR, further research is required.