Tracking Late AV Block Post-TAVR With Ambulatory ECG Monitoring

Patrice Wendling

June 05, 2019

Ambulatory rhythm monitoring may be a valuable surveillance tool for the underappreciated complication of delayed high-grade atrioventricular block (DH-AVB) following transcatheter aortic valve replacement (TAVR), new research suggests.

"There are still a lot of unknowns surrounding the risk of late AV block and it is important that we are looking into determining the risk factors," study author Karen Ream, PAC, University of Colorado School of Medicine, Aurora, told | Medscape Cardiology via email.

The investigators recently reported on a series of 158 of patients who underwent TAVR with newer-generation valves, in which 23 patients (14.5%) required new pacemaker placement before discharge and four patients re-presented with late heart block following uncomplicated TAVR. At 1-week follow-up with their primary cardiologist, an electrocardiogram (ECG) showed a widened QRS but no other significant changes for one of these patients, later found dead from intracranial hemorrhage as a result of syncope.

"This was concerning as there were no 'risk factors' or concerning features that would make us think this patient was at high risk for heart block," Ream said. "We've also seen an unexplained gap in mortality between hospitalization and 30 days that is concerning for the development of late heart block."

As a result, in October 2016 the team implemented routine use of real-time ambulatory rhythm monitoring (LifeWatch ACT Ex, LifeWatch, Zug, Switzerland) in all TAVR patients.

Their latest experience, reported May 28 in the Journal of the American College of Cardiology, involves 150 consecutive patients without a prior pacing device who underwent TAVR with Sapien 3 (Edwards Lifesciences) or Evolut-R and Evolut Pro (Medtronic) valves from October 2016 to March 2018. Fourteen of these patients were in the previous report.

All transmitted ECG tracings were reviewed first by the telemetry monitor staff and then by clinical staff. Additionally, medium-urgency alerts were triggered for patients with pauses lasting 3 to 5 seconds or with incident atrial fibrillation or flutter, and a fax sent to the ordering physician within an hour of detection.

The on-call electrophysiology physician was paged directly and patients contacted immediately upon detection of any high-urgency alert, which were prompted by a pause of more than 5 s, heart rate below 30 or above 200 beats/min, wide complex tachycardia, or H-AVB, defined as second-degree Mobitz II or third-degree AVB.

H-AVB requiring permanent pacemaker (PPM) implantation occurred in 18 patients before postprocedure day 2, one patient died, and 13 declined ambulatory electrocardiographic monitoring (AEM).

Late H-AVB, developing at least 2 days post-TAVR and requiring PPM implantation, was reported in 10% of the remaining 118 patients with remote monitoring at a median of 6 days postprocedure. All events occurred before routine 30-day clinical follow-up (range, 3 - 24 days). No serious adverse events or deaths occurred in those discharged with remote monitoring.

In Search of Predictors

Patients who developed any H-AVB were more likely to have hypertension (odds ratio [OR], 39.56; P = .013), TAVR with an Evolut valve (OR, 3.60; P = .019), or baseline right bundle branch block (RBBB) (OR, 45.1; P < .001) in multivariate analysis. RBBB, however, was the only significant predictor of late H-AVB (OR, 20.56; P = .004).

Although RBBB predicted both acute and delayed H-AVB with excellent specificity (98% and 94%, respectively), its sensitivity was very poor (30% and 27%, respectively).

"Therefore, although some temptation may exist to recommend prophylactic PPM implantation in all patients with RBBB undergoing TAVR, there remains insufficient data to support this practice," the authors say. "Additional efforts to identify other risk factors that may contribute to increased risk of H-AVB following TAVR should be explored, especially as indications and eligible patient populations expand for TAVR."

Development of new-onset left BBB (LBBB) after TAVR was a marker of significantly higher risk for PPM implantation and cardiac death at 1 year in a recent meta-analysis but was not significantly linked with H-AVB or delayed H-AVB in the current study, despite LBBB increasing from 11% pre-TAVR to 28.7% post-TAVR (<.001). The data might differ given the smaller sample size and shorter duration of follow-up, the authors suggest.

"These findings suggest that DH-AVB is an underappreciated complication of TAVR, and that routine AEM post-TAVR may be helpful in promptly identifying such patients, as well as in better clarifying risk factors for its development, Ream and her colleagues conclude.

Laying the Groundwork

"The current study provides the groundwork for the utility of AEM in post-TAVR patients in rapidly transitioning inpatients to an outpatient setting," Ulrika Birgersdotter-Green, MD, and Michael A. Eskander, MD, from the University of California, San Diego Health System, write in an accompanying editorial.

"Given the lack of sensitive pre-procedural electrocardiographic markers, AEM can certainly be a powerful tool in post-discharge surveillance and a potential bridge for the gap of the 8% to 10% 30-day morbidity and mortality in post-TAVR patients," they say.

Further work is needed to characterize risk factors for the development of H-AVB and late H-AVB, which may include ECG and imaging characteristics but also implantation techniques and an understanding of valve components and materials, according to the editorialists.

The investigators plan on completing a multicenter trial with more specific procedural data (prospective) and possible predictors, Ream said.

The research was funded in part by an educational grant from BioTelemetry, which had no role in study design, analysis, or manuscript development. Ream reported no relevant financial relationships. Birgersdotter-Green has received honoraria from Medtronic, Abbott, and Biotronik; served as a consultant for Medtronic; and received research grants from Abbott. Eskander reported no relevant financial relationships.

J Am Coll Cardiol. 2019;73:2538-2547 and 2548-2549. Abstract, Editorial

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