Development of new left bundle branch block (LBBB) following TAVR may be associated with an increased risk of mortality and hospital readmission as well as worse health status and lower left ventricular ejection fraction (LVEF), according to late-breaking clinical science presented Oct. 26 during TCT 2023.

Nickpreet Singh, MD, MS, et al., used data from the STS/ACC TVT Registry, including patients undergoing TAVR for aortic stenosis, between 2016 and 2022. Patients with pacemaker or ICD prior to TAVR or during index hospitalization, pre-existing conduction defect, unsuccessful TAVR or conversion to open heart surgery, cardiogenic shock or cardiac arrest on presentation, and urgent/emergent/salvage procedures were all excluded. Out of a total of 202,533 patients, 32,933 (16.3%) developed new LBBB following their TAVR procedure, defined as LBBB on either the post-procedure electrocardiogram (ECG) or 30-day ECG.

Study authors identified the primary outcome as all-cause mortality at one year. Patients with new LBBB after TAVR had significantly greater rates of all-cause mortality compared with patients without LBBB (adjusted hazard ratio [HR] 1.22, 95% CI 1.15-1.28; p<0.0001). This patient population also had greater likelihood of all-cause readmission (adjusted HR 1.26, 95% CI 1.22-1.30; p<0.0001) and requiring a new pacemaker (adjusted HR 3.62, 95% CI 3.38-3.88; p<0.0001) at one-year post-procedure.

Patients with new LBBB were also found to have slightly lower Kansas City Cardiomyopathy Questionnaire overall summary scores (adjusted difference –1.8 points, 95% CI –2.2 to –1.3; p<0.001) and LVEF (adjusted difference –2.8%, 95% CI –3.4% to –2.3%; p<0.001).

Study limitations included missing one-year outcomes data, lack of patient data after one-year following TAVR procedure and inability to adjust for unmeasured confounding factors like frailty.

"These findings suggest that continued efforts to limit the development of conduction disturbance after TAVR (irrespective of the need for permanent pacing) are warranted," write the authors. "Further study is needed to determine whether interventions to improve ventricular synchrony might improve outcomes in patients who develop new LBBB after TAVR."

In a separate late-breaking clinical trial, also presented at TCT 2023, Roger J. Laham, MD, FACC, et al., explored mechanisms underlying AV conduction abnormalities (AVCA) following TAVR, as well as sought to better understand the "potential utility of intraprocedural electrophysiologic study" to identify patients who may be at risk for AVCA.

In presenting the findings, researchers observed that alterations in both AV node and His Bundle function correlate with risk of heart block accompanying TAVR. They also noted that pre-existing right bundle branch block (RBBB) appears to predict risk for peri-TAVR, but not delayed complete heart block. New LBBB was not predictive, they said.

From a procedural standpoint, the study investigators said "clinicians caring for patients after TAVR should not assume that ECGs showing markedly prolonged PR intervals, or AV Wenckebach, represent delay or block in the AV node." They suggest that His bundle recordings can be performed by structural cardiologists and appear useful to predict risk for AV block.