Greater TAVR Experience May Lessen Risk of Conduction Abnormality
Left bundle branch block (LBBB) related to TAVR becomes less common as centers gain experience with the procedure. The improvement may stem from decreases in implantation depth, according to a study published online December 27, 2014, ahead of print in Catheterization and Cardiovascular Interventions.
A similar phenomenon, however, is not seen for permanent pacemaker requirement.
Although some progress has been made, Frits W. Prinzen, PhD, of the Cardiovascular Research Institute Maastricht (Maastricht, the Netherlands), and colleagues write, “elucidation of pathophysiologic mechanisms underlying these [conduction abnormalities] and subsequent changes in patient stratification, valve design, and the procedure are needed to further reduce this complication.”
The researchers looked at data from 549 patients (mean age 80.3; 45.2% men) without LBBB or a pacemaker who underwent TAVR at 4 centers (1 in Canada and 3 in the Netherlands) from January 2006 to July 2011. Roughly equal numbers of patients received CoreValve (49.5%; Medtronic) and the Sapien valve (50.5%; Edwards Lifesciences). Most underwent a transfemoral procedure (64.7%), and about one-third were treated via the transapical approach (32.5%).
“To study the effect of experience, patients were subdivided per participating center into equal tertiles based on the number of procedures, which were pooled to create 3 ‘consecutive’ cohorts,” the authors note. “This method was used to correct for the difference in initiation and number of patients of the [TAVR] program between individual centers.”
As experience increased, the overall median depth of implantation declined from 7.1 to 4.2 mm (P < .001), although the reduction was seen with CoreValve-treated patients only in a valve-specific analysis. Also, the percentage of patients with NYHA class III or IV symptoms before treatment fell from 91.2% to 73.6% (P < .001).
New LBBB developed in 33.7% of patients after TAVR, with that percentage decreasing from 42.6% to 27.3% (P = .006) as centers gained more experience. The trend was observed for patients treated with CoreValve (59.6% to 31.1%; P = .001) but not Sapien (22.6% to 24.8%; P = .11).
“The frequency of [TAVR]-LBBB is reduced by the increase in experience in conjunction with a significant reduction in the depth of implantation,” Dr. Prinzen and colleagues say.
Overall, 13.3% required new permanent pacemaker implantation after TAVR, a rate that did not change over time (P = .74).
On multivariate analysis, the only independent predictors of conduction abnormalities were depth of implantation for LBBB (OR 1.16; 95% CI 1.10-1.24) and preexisting right bundle branch block for permanent pacemaker implantation (OR 7.22; 95% CI 3.28-15.88).
More Needs to Be Done to Minimize Conduction Abnormalities
Dr. Prinzen said in a telephone interview with TCTMD that more concern is warranted for TAVR-related conduction abnormalities and other complications, particularly as the procedure becomes increasingly used in lower-risk populations.
Both LBBB and permanent pacemaker implantation “are associated with interventricular dyssynchrony, which in turn may affect cardiac performance and therefore [lessen the] benefit of the procedure, thereby affecting quality of life and eventually prognosis,” he and his colleagues write. They add that both complications have been associated with greater morbidity and mortality in patients with and without cardiovascular disease, although the evidence is conflicting in TAVR patients specifically.
Measures that can be taken to minimize these conduction abnormalities and optimize outcomes include refining indications for permanent pacemaker implantation after TAVR, individualizing valve selection, using new techniques like the direct aortic approach, being more selective in performing balloon predilatation, continuing training, guiding valve positioning, and improving catheter and valve technology, according to the authors.
van der Boon RMA, Houthuizen P, Urena M, et al. Trends in the occurrence of new conduction abnormalities after transcatheter aortic valve implantation. Catheter Cardiovasc Interv. 2014;Epub ahead of print.
- Dr. Prinzen reports no relevant conflicts of interest.