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Literature Review

The Influence of Native Aortic Valve Calcium and Transcatheter Valve Oversize on the Need for Pacemaker Implantation After Transcatheter Aortic Valve Insertion

Al-Azzam F, Greason KL, Krittanawong C, et al. J Thorac Cardiovasc Surg. 2017;153(5):1056-1062.

Reviewers: Marc Parris, MD MPH1; Antonio Hernandez Conte, MD MBA2

  1. Departments of Anesthesiology & Pediatrics, University of California Irvine Medical Center, Irvine, CA
  2. Diviision of Cardiac Anesthesiology, Kaiser Permanente Los Angeles Medical Center, Los Angeles, CA
Background

Recent studies have demonstrated that aortic valve calcium and the oversizing of valves in transcatheter aortic valve insertion (TAVI) may be associated with permanent pacemaker implantation. The authors posit a similar hypothesis and explore single-center data from their institution (Mayo Clinic) to explore the relationship of calcium burden, valve sizing, and the need for postoperative pacemaker implantation.

Methods

A retrospective review of 435 patients over a period of 6 years and 4 months yielded 300 eligible patients; patients excluded were those with inadequate imaging data and those who were deceased due to the operation. Thirty-day outcome data, as well as baseline patient demographics, electrocardiographic, and operative information was retrieved from various electronic medical records and databases. The authors studied balloon-expandable valves sized by annulus area and self-expanding valves sized by annulus perimeter (and converted to area for comparison). All measurements, including the valve calcium quantification, were derived from contrast and noncontrast ECG-gated CT scans. Oversizing was determined by an equation comparing the native valve area/perimeter to the prosthetic valve area/perimeter. Native aortic valve calcium and transcatheter aortic valve oversize were the variables in a multivariate model that was stratified by valve type and adjusted for baseline associations, bundle branch block, and factors previously shown to be associated with pacemaker implantation. The measured outcome was pacemaker implantation.

Results

Baseline characteristics were mostly similar in patients between prosthetic valve types, the most commonly implanted valve being SAPIEN by Edwards Lifesciences, but baseline PR interval was less in the balloon-expandable valves and percentage of prosthetic valve oversize was much greater in the self-expanding valve group when compared to balloon expandable, with median 40 (IQR, 26.9-57.1) vs 9.6 (IQR, 1.8-16.0). There was no difference in calcium scores between the valves. Postoperative permanent pacemaker implantation was performed in 59 patients (19.7%), and the most common indication due to high-degree atrioventricular block in 38 patients (64.4%). Other factors included in regression analysis were factors previously known to be associated with pacemaker implantation, which included PR duration >200 ms with atrial fibrillation, left or right bundle branch block, and use of a self-expanding valve. Logarithmic analysis of calcium score and untransformed valve oversize area were found to not be associated with permanent pacemaker implantation in this cohort. Insertion of a self-expanding valve and right bundle branch block were the only variables found to be predictive of pacemaker implantation.

Conclusion

Pacemaker implantation is common after TAVI and occurred in 1 out of 5 patients in this cohort. Multivariate analysis revealed that baseline right bundle branch block and self-expanding transcatheter valves were associated with pacemaker implantation while valve oversizing and calcium scores were not associated with pacemaker implantation. Associations with valve oversize have been found in other studies, but could not be compared to the current cohort due to type of valve employed and area measurement methods. Other studies have shown possible associations with calcium scores, but the studies were small in size or the results were not statistically significant. The authors posit that more specific or detailed ways of quantifying calcium burden may eventually reveal an association, but current evidence does not support the relationship. Other studies have shown that when compared to balloon-expanding valves, self-expanding valves are 2 to 4 times more likely to require pacemaker implantation. The data from this cohort concurs with this trend with an odds ratio of 4.09 (CI, 1.53-10.96, p = .005). This is thought to be due to the self-expanding valve being deployed lower in the left ventricular outflow track, causing an outward radial force that damages myocardium containing the atrioventricular conduction system. This study was limited by small sample size from a single center and pacemaker insertion technique improvement which may bias data due to excluded patients based on incomplete scans.

Comments

Various studies about pacemaker implantation and outcomes after TAVI have been conducted and have shown an association between distortion of myocardium and preexisting bundle branch block with pacemaker implantation. Kim et al.1 in a study with 121 TAVR patients across 6 medical centers showed an association between perimeter stretching due to the valve and placement of the valve relative to the noncoronary cusp, while Maan et al.2 in a study with 137 TAVR patients in a single center showed that right bundle branch block and prosthetic size relative to left ventricular outflow tract was associated with pacemaker implantation. This slightly larger study corroborates these findings; an association was found with right bundle branch block and self-expandable valves that may injure myocardium upon deployment. Further research in this area should focus on gathering data from multiple centers to improve statistical power and explore the mechanism of myocardial or conduction injury with prosthetic deployment. Lastly, considering that TAVIs are an evolving field, the experience of the clinician performing the procedure should be considered, as that could be a factor influencing postprocedural outcomes.

References

1. Kim WJ, Ko YG, Han S, et al. Predictors of permanent pacemaker insertion following transcatheter aortic valve replacement with the CoreValve Revalving system based on computed tomography analysis: an Asian multicenter registry study. J Invasive Cardiol. 2015;27(7):334-340.

2. Maan A, Refaat MM, Heist EK, et al. Incidence and predictors of pacemaker implantation in patients undergoing transcatheter aortic valve replacement. Pacing Clin Electrophysiol. 2015;38(7):878-886.

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