TAVR-Linked Conduction Abnormality Worsens Functional Status, but Not Mortality
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Nearly 20% of patients who undergo balloon-expandable transcatheter aortic valve replacement (TAVR) experience the conduction abnormality left bundle branch block (LBBB), which is associated with higher rates of permanent pacemaker implantation and less improvement in left ventricular ejection fraction (LVEF). However, LBBB is not associated with increased mortality or rehospitalizations, according to findings appearing online January 15, 2014, ahead of print in JACC: Cardiovascular Interventions.
Researchers led by Josep Rodés-Cabau, MD, of the Quebec Heart and Lung Institute (Quebec, Canada), looked at 668 consecutive patients not suitable or at very high risk for surgery who underwent TAVR at 4 Canadian centers with a balloon-expandable valve. None of the patients had pre-existing LBBB or a permanent pacemaker.
New Persistent LBBB in More Than 1 in 10 Patients
New-onset LBBB occurred in 128 patients (19.2%) immediately after the procedure. The conduction abnormality persisted at hospital discharge in over half of these (n = 79), representing 11.8% of the overall cohort.
Patients with new-onset persistent LBBB were younger (P = 0.006), had a higher incidence of hypertension (P = 0.040) and diabetes (P = 0.005), and more frequently underwent TAVR via the transapical approach (P = 0.005) and with a 29-mm valve (P = 0.041). On multivariate analysis, transapical approach (OR 1.9, 95% CI 1.15-3.16; P = 0.013) and a 29-mm valve (OR 3.12; 95% CI 1.22-7.97; P = 0.017) remained independent predictors of new-onset persistent LBBB.
At a median follow-up of 13 months, total mortality was 28.3% (n = 189), 27.8% in patients with new-onset persistent LBBB (n = 22). On multivariable adjustment, there were no differences between the new-onset persistent and no new-onset persistent LBBB groups regarding overall mortality (HR 0.83; 95% CI 0.53-1.29; P = 0.538).
The lack of association between new-onset persistent LBBB and mortality persisted when a landmark analysis with a cutoff at 30 days was performed.
Conduction Abnormality Predicts Pacemaker Implantation
Of the 668 patients alive at discharge without permanent pacemaker implantation after TAVR, 29 (4.3%)—11 (13.4%) with new-onset persistent LBBB and 18 (3.0%) without new-onset persistent LBBB—required permanent pacemaker implantation during follow-up. Implantation was needed due to a high degree of or complete atrioventricular block (AVB; 55.5%), sinus node dysfunction (20.7%), symptomatic bradycardia (13.8%), and slow A-fib (10.3%). A high degree of or complete AVB was the reason for permanent pacemaker implantation at follow-up in 8 of the 9 patients with new-onset persistent LBBB, and was the only independent predictor of permanent implantation during follow-up (HR 4.29; 95% CI 2.03-9.07; P < 0.001).
No Association with Mortality, Hospitalizations
The overall rehospitalization rate at 13 months was 42.1%. On multivariable analysis, there was no association between new-onset persistent LBBB and all-cause hospitalizations (P = 0.154). However, the conduction abnormality was linked to poorer NYHA functional class at 6- and 12-month follow-up (P = 0.015 for both). On multivariate analysis, a higher baseline LVEF (95% CI 8.60 to -6.55) and new-onset persistent LBBB (95% CI -6.91 to -1.10) were the only independent predictors of a lack of improvement in LVEF at follow-up.
The authors note that the roughly 20% rate of new-onset LBBB after balloon-expandable TAVR is in accordance with previous studies. “Also in accordance with previous studies, about one-half of the conduction disturbances occurring after balloon-expandable valve implantation resolved within the few days after the procedure,” they write.
Dr. Rodés-Cabau and colleagues add that factors contributing to new-onset persistent LBBB may include permanent mechanical damage of the left conduction system with lower implantation of the stent valve frame and greater damage of the ventricular septum when the transapical approach and 29-mm valves are used.
Continued Vigilance Called For
In an accompanying editorial, Laurent Roten, MD, and Bernhard Meier, MD, both of Bern University Hospital (Bern Switzerland), note that while several studies have shown no association between new-onset LBBB and mortality, “we should continue to be vigilant about fluctuating AV conduction impairment after TAVI or any symptoms suggesting transient complete AV block. These patients should proactively undergo [permanent pacemaker implantation].”
Drs. Roten and Meier conclude that “[a]s indications for TAVI widen to younger patients with fewer comorbidities, it can be expected that the relative occurrence of conduction [blockages] will diminish.”
Luca Testa, MD, PhD, of Istituto Clinico S. Ambrogio (Milan, Italy), noted in an email communication with TCTMD that “it is reassuring when several studies show similar results, in particular when the topic relates to such a frequent event as LBBB after TAVI.” Even so, Dr. Testa continued, “it is not clear why the authors decided to exclude from their population those patients who received a permanent pacemaker during the hospitalization, as this event has been clearly linked to new-onset LBBB after TAVI.”
Current Rate Probably Lower
In an interview with TCTMD, Philippe Généreux, MD, of Columbia University Medical Center (New York, NY), noted that the 20% rate of new-onset LBBB is probably much lower in current practice. “These data are taken from the sickest patients with the oldest devices,” he said. “Now we’re in the fourth generation of devices, so I think the current rate of LBBB is probably lower given that we can better position the valve, we have better devices, and operators are more skilled and are better able to size the valve.”
Dr. Généreux added that “even in these sick patients it’s reassuring that [LBBB] is not associated with increased mortality. That being said, if you want to move forward into lower-risk populations, you want to optimize everything, and you don’t want to have a condition associated with poor functional status and a lack of improvement in EF. In the big scheme of things, we should do everything to avoid it, and newer devices, less sick patients, and better sizing and implantation level will make left bundle branch block less likely.”
Sources:
1. Urena M, Webb JG, Cheema A, et al. Impact of new-onset persistent left bundle branch block on late clinical outcomes in patients undergoing transcatheter aortic valve implantation with a balloon-expandable valve. J Am Coll Cardiol Intv. 2014; Epub ahead of print.
2. Roten L, Meier B. Left bundle branch block after TAVI: Still a matter of concern? J Am Coll Cardiol Intv. 2014; Epub ahead of print.
Disclosures:
- Dr. Rodés-Cabau reports serving as a consultant for Edwards Lifesciences and St. Jude Medical.
- Dr. Meier reports receiving research grants to his institution from Biotronik, Boston Scientific, Edwards Lifesciences, Medtronic, Sorin Group, and St. Jude Medical.
- Dr. Roten reports no relevant conflicts of interest.
- Dr. Généreux reports receiving speaker fees from Edwards Lifesciences.
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