Percutaneous transcatheter aortic valve replacement (TAVR) has established itself
as the preferred alternative to surgical valve replacement for inoperable high‐ and
lower‐surgical‐risk patients with severe aortic stenosis, but is associated with significant
risk of high‐grade atrioventricular block and pacemaker implantation. A concerning
trend is that the incidence of permanent pacemaker implantation (PPI) post‐TAVR has
actually increased significantly in recent trials that have tested latest‐generation
devices in intermediate‐ and low‐risk patients.1, 2
Mechanism of Injury to the Conduction System After TAVR
Although some risk factors for PPI post‐TAVR are operator dependent and may be potentially
modifiable, such as depth of valve implantation, presence of baseline conduction system
disease has remained one of the most reliable independent predictors for development
of advanced atrioventricular block after TAVR, regardless of device used.3 This was
first demonstrated in an analysis of 1973 patients with severe aortic stenosis who
underwent TAVR in the PARTNER (Placement of Aortic Transcatheter Valves) trial where
pre‐existing right bundle branch block and left anterior fascicular block at baseline
(P<0.001) were shown to be electrocardiographic predictors for post‐TAVR permanent
pacemaker, and these findings have remained consistent in subsequent analyses.4
The extent of injury to the conduction system caused by mechanical trauma during TAVR
is often capricious and not all cases of procedure‐related atrioventricular block,
even when initially severe, remain long‐lasting. It is believed that anatomic variation
in the length and location of the penetrating segment of the bundle of His and the
depth of the proximal portion of the left bundle affect susceptibility to injury.5
Given the dynamic nature of TAVR‐related injury/inflammation, European Society of
Cardiology guidelines for cardiac pacing suggest an observation period of at least
7 days to assess for potential return of functional atrioventricular conduction before
deciding whether to move forward with implantation of a permanent pacemaker.6 However,
time for recovery from conduction disturbances is often unpredictable and may take
longer than 1 week, contributing to wide variation in practice patterns for implantation.
Device selection has been demonstrated to be an important modifiable risk factor for
post‐TAVR PPI. Incidence of TAVR‐related atrioventricular block requiring PPI was
shown to be substantially higher with first‐generation SE Corevalve than BE Sapien
X3 devices. While improvements in design were incorporated into the latest BE technologies
(Sapien 3, Sapien 3 Ultra), rates of PPI because of iatrogenic atrioventricular block
have also increased considerably in comparison to the predecessor Sapien XT valve
despite having tested newer BE valves in lower‐risk populations.7 Other device designs
have aimed to lower risk of PPI after TAVR by mitigating trauma to the atrioventricular
conduction system. In the SAVI TF (Symetis ACURATE neo Valve Implantation Using Transfemoral
Access) registry, PPI was low using the ACURATE Neo valve despite its SE design, and
in a prospective comparison the platform had lower incidence of post‐TAVR PPI than
other SE and BE valves ([Accurate Neo] 6% versus [Corevalve] 25% versus [Sapien XT]
11%; P=0.013) because of lower generation of radial forces and supra‐annular position
during deployment.8, 9 Unfortunately, in the SCOPE (Safety and Efficacy Comparison
Of Two TAVI Systems in a Prospective Randomized Evaluation) I trial the ACURATE Neo
valve did not meet noninferiority compared with the Sapien 3 valve for the primary
efficacy end points of the study because of higher rates of a peri‐vavular leak.10
Insights From a 10‐Year Experience With Pacemaker Implantation After TAVR
In this issue of the Journal of the American Heart Association (JAHA), Fauchier et al11
present the results of a systematic analysis of patient data from a national hospital
administration database of 49 201 patients who had severe aortic stenosis and who
underwent TAVI procedures using Edwards Sapien BE (Sapien XT and Sapien 3) or Medtronic
SE (Corevalve and Evolut) bioprosthetic valves between 2010 and 2019. During study
follow‐up (mean 1.2 years; 59 041 patient‐years), 27% of patients in the cohort underwent
PPI post‐TAVR with the majority performed within 30 days, which is a higher incidence
than reported in most other large studies. As expected, the rate of PPI implantation
was higher for SE than BE devices in the cohort, although the difference was only
modestly higher than the Sapien XT group (Corevalve: hazard ratio [HR], 1.3 [95% CI,
1.21–1.4]; Evolut: HR, 1.25 [95% CI, 1.21–1.34]). A unique finding of the study was
the lack of difference in the rate of PPI between patients who underwent TAVI with
early and later generation BE technologies (Sapien 3: HR, 1.01 [95% CI 0.95–1.08]
[reference Sapien XT]). However, PPI was lower in the Sapien 3 group during the first
30 days after TAVR, albeit with a small absolute difference (1.2%) between Sapien
3 and Sapien XT devices likely only reaching statistical significance because of the
large number of patients in both groups. A curious finding of the study that merits
further explanation was the higher incidence of late PPI performed in the Sapien 3
arm despite lower Charleston Comorbidity and Frailty Index scores than the Sapien
XT arm. In the multivariate analysis, the usual suspects were confirmed as risk factors
for PPI post‐TAVI including age, right bundle branch block, hypertension, type 2 diabetes
mellitus, history of myocardial infarction, and implantation of SE bioprosthetic valves.
A novel finding of the study was that pre‐existing left bundle branch block (LBBB)
was identified as a predictor for PPI post‐TAVR. Considering evidence that new‐onset
LBBB may be associated with adverse outcomes post‐TAVR, higher presence of baseline
LBBB in the Sapien 3 group than in the Sapien XT group (17.4% versus 12%) may have
contributed to treatment bias, helping explain the higher incidence of PPI during
later follow‐up in the Sapien 3 group. However, it should be remembered that there
is no conclusive evidence in the literature that pre‐existing LBBB actually increases
risk of trauma‐related atrioventricular block after TAVR.
With over 49 000 patients, the size of the study population is a major strength of
the current analysis. Although incidence of PPI implantation was higher than findings
reported in most other studies, the current analysis is insightful in view that it
represents a real‐world experience with a large number of operators minimizing the
influence of individual practice variance. The investigators bring up a valid point
that external pressure regarding length of stay in the hospital and hastening mobilization
may have led to more “aggressive” decisions to proceed with PPI rather than fully
wait out recovery of atrioventricular conduction or new‐onset LBBB. Although follow‐up
data earlier than 30 days (ie, index hospitalization) were not made available in the
current analysis, results from other studies have suggested that lack of clear guidance
on appropriate timing for PPI and treatment bias have increased the proclivity for
PPI in TAVR patients, as restoration of atrioventricular conduction after PPI has
been reported in up to 50% of patients during follow‐up. Another important limitation
of the study was the decision to include patients with prior cardiovascular implantable
devices in the analysis. As presence of existing cardiovascular implantable devices
would have excluded patient eligibility for PPI post‐TAVR, the higher proportion of
existing cardiovascular implantable devices in patients who underwent SE valve implantation
in the study may have led to underestimation of actual risk estimates for PPI, especially
for the Corevalve SE arm (26.5% [Corevalve SE] versus 19.5% [reference Sapient XT]).
Finally, many of the clinical variables identified in the multivariate analysis were
only small to modest in size despite reaching statistical significance in the model.
The predictors with largest effect size and therefore most clinically significant
were presence of right bundle branch block and LBBB at baseline. For patients with
existing right bundle branch block, incidence of PPI was higher in the first 30 days
(odds ratio [OR], 2.21; [CI, 2.03–2.40]) than the rest of follow‐up (OR, 1.34; [95%
CI, 1.14–1.58]). Conversely, risk of PPI in patients with pre‐existing LBBB was lower
during the first 30 days (OR, 1.35; [95% CI, 1.27–1.42]) but increased on follow‐up
(OR, 1.75; [95% CI, 1.58–1.93]). From the results of the study it is unclear whether
progression to complete heart block or other reasons led to PPI after 30 days in patients
with existing LBBB at baseline.
Future Outlook
The relevance of procedure‐related conduction disturbance and subsequent permanent
pacemaker placement is likely to increase as indications for TAVR expand further to
younger and lower‐risk patients. While mortality may not be higher in patients who
undergo PPI after TAVR,12 post‐TAVR PPI is still a complication associated with increased
length of stay, rehospitalizations, and other associated cost burdens. Furthermore,
PPI is also associated with its own hazards such as risk of hematoma, vascular injury,
serious infection, pneumothorax, lead dislodgement, and tricuspid regurgitation, potentially
mitigating the advantages offered by TAVR. The future role of electrophysiology studies
to stratify patients with equivocal findings on ECG post‐TAVR needs to be studied
further, but interpretation of electrophysiology study results are likely to be limited
by the same constraints that challenge clinical assessment, given the dynamic nature
of conduction system injury after TAVR and variable time length of recovery between
patients. Because pacing and LBBB‐induced cardiomyopathy remain a potential concern
post‐TAVR, cardiac resynchronization therapy may play an increased role in future
management of TAVR patients. In a recently published study, De Pooter et al demonstrated
feasibility of permanent His bundle pacing in a cohort (n=16) of patients with TAVR‐induced
LBBB. His bundle pacing with recruitment of the LBBB was obtained in 69% (11/16) of
patients with significant narrowing of QRS duration. Although mean threshold for LBBB
correction was somewhat high at 1.9 V±1.1 ms at 1.0 ms, threshold remained stable
after 11 months of follow‐up.13
Conclusions
The current study by Fauchier and colleagues confirms that despite closing the gap
with surgical valve replacement in terms of mortality and overall procedural safety,
there has been minimal progress so far in reducing the incidence of procedure‐related
conduction abnormalities necessitating PPI despite technological advancements and
increased operator experience. As the TAVR population continues to expand towards
a younger and healthier population, traditional risk factors of value for older and
high‐risk patients will likely become less predictive for identifying patients at
risk of requiring PPI before TAVR. Therefore, there is a pressing need to develop
bioprosthetic devices and delivery systems that minimize trauma to the atrioventricular
conduction system and establish clear clinical guidelines for indications for permanent
pacemaker placement in patients after TAVR.
Disclosures
Dr Huang has served as a consultant for Biosense—Webster, Medtronic, Biotronik, and
Cardiofocus; has a research grant from Medtronic. Dr Mansour has served as a consultant
for Biosense—Webster, Abbott, Medtronic, Boston Scientific, Janssen, Baylis, Philips,
Novartis, and Sentre Heart; has received research grants from Biosense—Webster, Abbott,
Boston Scientific, Medtronic, Pfizer, Boehringer Ingelheim; and has an equity interest
in EPD Solutions, NewPace Ltd, and Affera.