Abstract Body: Background: Interventricular dyssynchrony is a well-established complication of dual-chamber transvenous pacemakers, though few studies have established this risk with single-chamber leadless pacemakers. These devices are frequently employed for conduction disturbances after transcatheter aortic valve replacement (TAVR), which necessitates further understanding of their potential impact on dyssynchrony.

Objective: The aim of this retrospective study was to evaluate for interventricular mechanical delay and dyssynchrony in patients receiving a leadless pacemaker for conduction disturbances after transcatheter aortic valve replacement (TAVR).

Methods: This is a retrospective study of 19 adult patients (age: 80.2 ± 7.2, female: 63.1%) who underwent TAVR and subsequently received a leadless pacemaker Micra VR (n =4; 21.0%) or Micra AV (n = 15; 78.9%). Pre-TAVR, post-TAVR, and post-pacemaker echocardiograms were evaluated for interventricular mechanical
conduction delay (IVMD) with patients serving as their own controls. A cutoff IVMD value of >40ms was used to identify the presence of interventricular dyssynchrony.

Results: As compared to pre-TAVR echocardiograms, there was a significant increase in IVMD on post-TAVR echocardiograms from -5.8 ±22.9 to 24.8 ±29.2 (P = 0.001). Post-TAVR conduction disturbances for which a pacemaker was indicated included complete heart block (CHB; n= 14; 73.7%), atrial fibrillation with slow
ventricular response (n= 3; 15.8%), mobitz type II second-degree heart block (n = 1; 5.3%) and symptomatic bradycardia with first-degree heart block (n= 1; 5.3%). After leadless pacemaker placement, there was a non-significant trend towards decreased IVMD between post-TAVR and post-pacemaker echocardiograms 24.8 ±29.2 vs. 10.1±33.5 (P = 0.112).

Conclusion: This retrospective analysis revealed a significant increase in IVMD after TAVR that later improved after leadless pacemaker placement. The finding persisted despite controlling for LBBB and TVP and may be explained by subtle TAVR-induced conduction delays that did not result in overt LBBB. After Micra placement, average IVMD decreased, indicating a trend towards decreasing interventricular dyssynchrony. This may be explained by improved AV synchrony with Micra AV systems that may synergistically lead to improved interventricular dyssynchrony through stabilized right and left ventricular filling and balanced interventricular activation patterns.