Abstract 17172: Paradoxical QRS Narrowing After Transcatheter Aortic Valve Replacement Concealing New Left Bundle Branch Block

Abstract

Introduction: Left bundle branch block (LBBB) after transcatheter aortic valve replacement (TAVR) is common and is a risk factor for high-grade atrioventricular (AV) block. We report a case of paradoxical QRS narrowing after TAVR in a patient with pre-existing incomplete right bundle branch block (iRBBB). Such QRS narrowing, masquerading as improved AV conduction, may conceal the development of new LBBB. Case Presentation: An 81-year-old man with severe aortic stenosis underwent TAVR with a 29mm Medtronic Evolut transcatheter self-expanding bioprosthetic valve. Post-operative TEE showed a well-seated valve without paravalvular leak. Preoperative ECG demonstrated sinus rhythm, 1 st degree AV delay (230 ms), and iRBBB (QRS 110 ms) (Fig. 1A). Immediately after TAVR, ECG showed a narrowed QRS (90 ms) with normal morphology (Fig. 1B). A narrowed QRS was sustained on post-operative day 2, with prolongation of the PR interval (260 ms; Fig. 1C). Electrophysiology study (EPS) showed a prolonged HV interval (65 ms) but no inducible block (Fig. 1D), and an implantable loop recorder (ILR) was placed. Discussion: Damage to the infranodal cardiac conduction system after TAVR is common, and approximately 15% of post-TAVR patients require pacemaker, with a higher occurrence in self-expanding valves as compared to balloon-expandable valves. Pre-existing RBBB as well as new-onset LBBB after TAVR increase the risk for heart block. Here, QRS normalization of an iRBBB concealed the development of new LBBB, by way of balanced delay in both the right and left bundles. This balanced delay is evident in the slightly longer PR interval post-operatively. Such a finding may be falsely reassuring and requires increased scrutiny (such as EPS and ILR placement). Conclusion: This case illustrates that paradoxical normalization of AV conduction following TAVR may belie an increased risk of high-grade AV block. Structural heart teams should be aware of this potential post-operative complication.