Permanent pacemaker (PPM) implantation continues to be a significant complication of transcatheter aortic valve replacement (TAVR), occurring in approximately 12% of patients . While device enhancements of new TAVR valves, better patient selection and operator experience have led to a decrease in paravalvular regurgitation, vascular injury, stroke, and new dialysis requirement, pacemaker implantation appears to be the only complication that is increasing in frequency . As TAVR expands to patients with lower risk, the long-term consequences of pacemaker implantation will likely be amplified. In the PARTNER (Placement of AoRtic TraNscathetER Valves Trial; NCT00530894 ) trial new PPM was associated with a longer duration of hospitalization and higher rates of repeat hospitalization and mortality or repeat hospitalization at 1 year .

Due to the proximity of the virtual annulus to the conduction system, atrioventricular (AV) conduction disturbances are noted in the majority of patients undergoing TAVR when electrophysiological study (EPS) is performed before and after the procedure . Defining which EPS abnormalities may be indicative of long-term PPM requirement is of clinical importance in particular among patients with new left bundle branch block (LBBB). In this issue of Journal of Cardiovascular Revascularization Medicine , Makki et al. provide a retrospective review of 24 patients who underwent TAVR complicated by pacemaker implantation . The rate of pacemaker implantation (14% of total cohort) was consistent with prior studies. Seven patients developed new LBBB and underwent EPS following TAVR. All 7 of these patients received their pacemaker for the indication of new LBBB with abnormal EPS and only 1 of these 7 patients (14%) remained pacemaker-dependent at follow-up. In total, pacemaker dependency, defined as underlying asystole, complete atrioventricular (AV) block, or >50% pacing burden, occurred in 8/24 (33%) of patients during a mean follow-up of 22 months. Seven of these 8 patients (88%) had resting complete heart block while the other had complete heart block induced at EPS. These data suggest that a “clinical indication” for PPM (i.e. complete heart block) was a stronger predictor of pacemaker dependency at follow-up than an “EPS-based indication” and raises the question of what is the optimal definition of an abnormal EPS that one should use for clinical decision making after TAVR. For this study the authors used HV > 55 ms or elicitation of complete heart block during EPS.

Previously Kostopoulou et al. prospectively evaluated 45 patients undergoing TAVR with the CoreValve randomized to EPS or electrocardiographic monitoring alone . Fourteen patients (31%) developed new LBBB and pacemaker implantation was required in 10 patients (22%) within 1 month, all due to complete AV block. Univariate analysis revealed that the baseline HV interval predicted complete heart block while an HV interval > 70 ms predicted pacemaker implantation. At 1 month follow-up only 4 of the 10 patients (25%) receiving a pacemaker remained pacemaker-dependent and 2 of the 3 patients with baseline HV interval > 70 ms remained pacemaker-dependent.

In a prospective study of 75 TAVR patients by Rivard et al., 11 patients (14.7%) developed AV block during index hospitalization and 3 patients (4.0%) after hospital discharge with a median follow-up of 1.4 years . In multivariate analysis the delta-HV interval (HV interval after TAVR minus the baseline HV interval) was the only factor independently associated with complete AV block (HR 1.152 ms, 95% CI 1.063–1.248, p = 0.006). Among patients with new LBBB the HV interval after TAVR was also strongly associated with AV block. The sensitivity and specificity by receiver operating curve for predicting AV block were 100% and 84.4%, respectively, for delta-HV interval ≥ 13 ms and 83.3% and 81.6%, respectively, for HV interval ≥ 65 ms after TAVR. Interestingly, in a multivariate analysis, the HV interval after TAVR was also independently associated with mortality (HR 1.073 per ms; 95% CI 1.029–1.119; p = 0.001).

Based on these findings Rivard et al. proposed an algorithm for managing patients before and after TAVR . Consistent with current practice, any patient who develops complete AV block should receive a pacemaker prior to discharge. If patients develop new LBBB the authors suggest that they should undergo EPS and receive a permanent pacemaker if their HV interval is ≥65 ms. Finally, patients with baseline LBBB should undergo EPS before and after TAVR and should receive a permanent pacemaker if their delta-HV interval is ≥13 ms.

All of these studies address the utility of EPS in helping to decide which patients will benefit from pacemaker implantation. They also highlight the ongoing difficulty in predicting which patients will remain pacemaker-dependent. While the proposed criteria and algorithms proposed could contribute to the decision of when to implant a permanent pacemaker, additional large, prospective trials are needed to address these questions further and, hopefully, lead to more uniform guidelines.