Electrical Variables, Not Valve Type, Predict Need for Pacemaker After TAVI

LONDON, ENGLAND—New research has identified several high-risk variables associated with the need for a new permanent pacemaker after TAVI for aortic stenosis. None on the list are among the more common predictors.

Baseline right bundle branch block (RBBB), pre-TAVI rapid atrial pacing (RAP)-induced Mobitz I, which is a type of second-degree atrioventricular (AV) block, and any changes in the HV interval before and after TAVI each significantly predicted the need for a permanent pacemaker.

The use of an oversized prosthesis and implantation with a self-expanding valve, however, were not linked to a need for a new pacemaker.

“I was very surprised by this result,” said lead investigator Karan Rao, MD (Complete Health Australia, Sydney, Australia). “If you look at the univariate analysis, [use of the self-expanding valve] is a predictor, but perhaps what this is suggesting is that when you adjust for all the other factors, the difference between self-expanding values and the balloon-expanding valves is not as wide as we initially thought.”

Rao, who presented the CONDUCT-TAVI study last week at PCR London Valves 2024, said that even with some of the newer devices, pacemaker rates have remained stubbornly high. Historically, the risk of needing a new pacemaker is lowest in patients treated with a balloon-expandable valve—rates are in the single digits in the PARTNER trials, for example—and higher with self-expanding valves. In the Evolut Low Risk trial, nearly one in five patients needed a pacemaker after the procedure. More recently, pacemaker rates were 15% with the balloon-expandable Myval device (Meril Life Sciences) in the LANDMARK study and 12% with the Acurate neo2 self-expanding valve (Boston Scientific) in the investigational device exemption study.  

“If you look at a lot of smaller, specialized studies, they seem to suggest that pacemaker rates are plummeting,” Rao told TCTMD. “But if look at the major randomized controlled trials, they seem to suggest that since inception the pacemaker rates haven't fallen that much. For that reason, I think it's still a major problem. Also, a lot of the rates that are reported are either at discharge or 30 days, but when you extend it out to 1 year, you're missing 3% to 5% of patients not captured in early data.”

Rao said there are a number of known anatomical, procedural, and electrical risk factors for AV block after TAVI, but that investigators still aren’t very good at accurately predicting who will require a pacemaker after the procedure. This poses a problem, particularly in the push for same-day discharge, he said.

Predicting Who Won’t Need a Pacemaker

The prospective CONDUCT-TAVI study was designed to assess the incidence and timing of pacemaker implantation due to AV block in the first year after TAVI. One of the secondary aims was to assess the incidence of new tachyarrhythmias, particularly atrial fibrillation (AF).

In total, 200 patients (mean age 82.2 years; 64.5% male) were included in the study, all of whom underwent an electrophysiology (EP) study to measure the AH and HV intervals, as well as undergo RAP (70 to 120 beats per minutes) before and after TAVI to “essentially stress test the AV node to determine its health,” said Rao. In total, 61.5% were treated with a self-expanding valve while 38.5% received a balloon-expandable device.

Within 48 hours, 27 patients (13.5%) required a pacemaker due to second-degree AV block. Between 48 hours and 1 year, another 21 patients required a pacemaker, with 16 patients getting one due to AV block and five for tachycardia-bradycardia syndrome. Among the 173 patients who didn’t require a pacemaker and received an implantable loop recorder at discharge, new-onset AF was diagnosed in 15% at 1 year.    

Rao said that while pacemaker implantations are clustered in the first 48 hours, “the risk doesn’t completely go away until 1 year.” With AF, the risk is clustered in the first 100 days, but also remains present out to 1 year.

In a multivariate model, baseline RBBB was associated with a more than sixfold increased risk of needing a new pacemaker. Similarly, pre-TAVI RAP-induced Mobitz 1 (also known as Wenckebach block) was associated with a fivefold higher risk of pacemaker implantation. Any change in the HV interval before and after TAVI was associated with a 6% higher risk of needing a permanent pacemaker.

“If you could avoid those three major risk factors, you had a very high negative predictive value of not needing a pacemaker,” said Rao. “In our cohort, we could say that with 98% certainty you would not a pacemaker at 1 year. This could help us pick out the patients that can be discharged early and get us one step closer to same-day discharge.”

Membrane septum depth, implantation depth, and valve type, on the other hand, were not associated with the adverse outcome. 

To TCTMD, Rao noted that EP studies are not standard during TAVI, nor are the use of implantable loop recorders. In terms of how the study impacts their practice, he said that if a patient has preexisting RBBB, or develops new bundle branch block after TAVI, they will keep them in hospital for a day or two longer to see if they might need a pacemaker before going home.

There are limitations to their research, said Rao, noting that this in an observational, nonblinded, single-arm study. Also, the decision to implant a pacemaker was left to the discretion of the treating cardiologist. In terms of implanting the valves, all operators used the cusp-overlap technique, which may have helped “close the gap” between self-expanding and balloon-expandable valves, he added.