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.