DISCUSSION
The current nationwide study evaluates the need for pacemaker placement
during six-month follow up in patients after TAVR. The novel findings of
this study that deserve emphasis are a) most pacemaker implantations
occur within 14 days of discharge b) There is a sudden increase in
pacemaker implantation after TAVR implantation that steadies at 20 days
c) Most common primary reasons for readmission needing pacemaker
implantation is complete heart block.
The STS TVT registry from 2011 to 2014 reported the median time to
pacemaker implantation to be 3 days, and occurring often occurring at
the time of index TAVR(12). This correlated with early experience of
TAVR in the United States and first-generation devices. Our study
selects a more contemporary cohort with inclusion of all-payer patients
in the analysis. Our study also reflects patients who received TAVR
valves after the FDA expanded the indication to intermediate risk
patients that may reflect a lower burden of comorbidities. Our study had
a nationwide sample with almost 2/3rds of patients getting PPMI at 14
days suggesting that it could be a reasonable timeframe to clinicians
who can monitor at-risk patients for timely detection of need for
permanent pacemakers though median time to PPMI was almost a month after
TAVR implantation. It also has implications on discharge planning for
patients who may be candidates for early discharge
The factors that adequately predict at-risk patients are multiple and
currently non-standardized(2, 13, 14). In a study of 611 patients, a
higher prevalence of right bundle branch block and change in PR interval
was predictive of delayed conduction disturbances.(15). Other factors
like advanced age (>75 years) and male gender have been
shown to predict pacemaker implantation(4, 12). Certain risk scores that
include pre-TAVR characteristics are tailored towards predicting
periprocedural pacemaker implantations(16). Several studies have
stressed the utility of pre- and post- procedural ECG changes to
identify patients at risk of delayed pacemakers, their findings however
have been inconsistent. (7, 15, 17) A single center study even observed
normal PR and QRS intervals at discharge .(6) The low incidence of
pacemaker implantation after discharge may be a barrier to robust
modelling and prediction. Even in our study, we found limited clinical
differences in patients receiving a pacemaker post discharge compared to
the patients who did not, suggesting a lack of clear predictor
variables. Moreover, the lack of echocardiographic and procedural
characteristics limits the prediction in our study.
Our study also evaluates the reasons for receiving pacemaker at
readmission. Almost half of the patients underwent pacemaker
implantation for complete heart block with a minority requiring it for
other higher degree AV blocks. It could perhaps be that the patient’s AV
conduction system fails progressively in the unmonitored outpatient
setting, until complete cessation of conduction. Other probable causes
include sudden complete cessation of conduction down the AV node,
without evidence of progression, either post procedural or during
follow-up or intermittent but symptomatic advanced heart block. Factors
like cuff swelling or progressive valve stent frame expansion that may
account for early presentation of heart block but may not explain the
presentation beyond 14 days. (6) In a cohort of 150 patients monitored
for thirty days after TAVR, 12(8%) developed delayed AV block with 75%
developing complete heart block and rest developing second degree AV
block(10). The study also showed than up to 40% of patients were
symptomatic. Thus, further studies are needed to evaluate for natural
history of conduction system disease after TAVR.
The length of stay was longest in patients who received pacemaker during
the index admission of all three groups in our study, as has previously
been reported. Interestingly, hospital stay was shortest for patients
who subsequently received a pacemaker on follow up. This may suggest an
uneventful index TAVR perhaps due to a lower burden of comorbid
conditions leading to early discharge. Additionally, 9.5 % of patients
had advanced AV block at index admission but underwent PPMI in
follow-up. (Table 2). This may suggest failure to identify risk of
incident conduction disease meriting PPMI in a shorter hospital
observation period or presence of conduction disorders that may have
been transient during TAVR implantation or have resolved prior to
discharge. Newer expert opinion does provide a direction towards
follow-up of these patients, however the optimal timing of discharge
after TAVR remains open to debate.(8) If certain patients are selected
for early discharge, the post-discharge risk of unplanned pacemaker
implantation may be mitigated by continued short-term rhythm monitoring.
Several single center studies have used wearable or implantable monitors
(9-11), but protocolized follow up monitoring is needed for large scale
implementation.