Permanent Conduction-System Pacing After TAVR? Don’t ‘Diss the His’

Physiologic pacing of the His-Purkinje conduction system is feasible in patients who require a permanent pacemaker following TAVR and this alternative pacing method did not interfere with ejection fraction recovery in patients with reduced LV function at baseline, according to the results of a new retrospective study.

Overall, operators had better success pacing the left bundle branch area compared with the His bundle, but reported greater success pacing the His bundle in patients treated with the balloon-expandable Sapien valve (Edwards Lifesciences) than in those treated with the self-expanding CoreValve (Medtronic).

The new results, released as an “e-poster” at the virtual 2020 Heart Rhythm Society Scientific Sessions and published in JACC: Clinical Electrophysiology, suggest that pacing the His-Purkinje conduction system may potentially reduce electromechanical dyssynchrony associated with standard right ventricular (RV) pacing.

“There are two issues,” said lead investigator Pugazhendhi Vijayaraman, MD (Geisinger Heart Institute, Wilkes-Barre, PA), explaining the rationale for conduction-system pacing. First off, RV pacing in patients with atrioventricular (AV) block “does cause a certain degree of cardiomyopathy and heart failure,” he said. The second issue pertains specifically to TAVR patients.

“They are a particularly vulnerable group in that many may have underlying heart failure,” he said. Aortic stenosis, along with left ventricular hypertrophy, places them at a somewhat increased risk of heart failure after a pacemaker. “We fix the valve and roughly 20% need a pacemaker—different studies have different numbers, with different types of valves—but we increase the risk of heart failure or worsen heart function from pacing. [Conduction system] pacing would hopefully avoid that.”

Pacing of the His-bundle conduction system has previously been shown to be associated with a reduction in the risk of heart failure hospitalizations and pacing-induced cardiomyopathy, said Vijayaraman, although not specifically in patients with a conduction disturbance after TAVR.    

Retrospective Series Backs the Concept

In the retrospective series, which included four US hospitals and one center in Spain, the researchers identified 65 patients (mean age 79 years; 57% men) requiring ventricular pacing following TAVR in whom permanent pacing of the His-Purkinje conduction system was attempted. The mean LVEF at baseline was 58%, with 11 patients having an LVEF ≤ 50%. AV conduction disease with infranodal AV block was present in 89% of patients while sinus node/AV node dysfunction was present in four patients. Three patients had left bundle branch block, LV dysfunction, and heart failure. Mean follow-up duration was 12 months.

His-Purkinje conduction-system pacing was successful in 55 patients. His-bundle pacing was attempted in 46 patients and successful in 63% of cases. For the 17 patients where His-bundle pacing was unsuccessful, high thresholds and an inability to recruit distal conduction were the reason for the failure. For 28 patients in whom left bundle branch area pacing was attempted, it was successful in 26 patients. The majority (78.5%) of patients were treated with the Sapien valve, and His-bundle pacing was successful in 69% of these cases but only in four of nine CoreValve-treated patients.

“If your lead location happens to be proximal to the site of the block, often the threshold required to correct it is high,” said Vijayaraman, explaining the His bundle failures. “So we’ll try to get to the distal site—the His bundle travels from the right to the left side, and in some patients it goes ‘deep’ very early—and we can’t reach the distal site so the success rate is lower with His-bundle pacing in TAVR patients.”

With respect to the different success rates with the different valves, he said the balloon-expandable Sapien has a “smaller footprint,” while CoreValve may continue to expand a little bit after implantation, which can cause a little more extensive heart block that makes His-bundle pacing a challenge.

His-Purkinje conduction-system pacing led to a narrowing of the QRS duration from 138 ms at baseline to 127 ms. There was a nonsignificant reduction in QRS duration with His-bundle pacing and a significant reduction in QRS duration with left bundle branch area pacing. In terms of echocardiographic outcomes, LVEF was unchanged during follow-up, as was left ventricular end-diastolic diameter. For the 11 patients with LVEF ≤ 50%, conduction-system pacing was successful in 10 patients and LVEF significantly improved in eight patients with follow-up echocardiograms.

There were no acute procedure-related complications reported in the series. Eight patients died during follow-up, including two patients with underlying cardiomyopathy from progressive heart failure. There were four patients hospitalized for heart failure, all with preexisting cardiomyopathy and heart failure.

Need to Show ‘Clinical’ Advantage Still

In an editorial, Jordana Kron, MD, and Santosh Padala, MD (Virginia Commonwealth University, Richmond, VA), note that TAVR is now indicated for all patients regardless of their baseline surgical risk and question whether conduction-system pacing should now be routinely performed in all TAVR patients with heart block to decrease the long-term morbidity associated with RV pacing.

At present, they say more studies are needed to confirm the findings, but do suggest in patients expected to have a “high burden of long-term ventricular pacing,” it might be better to preference left bundle branch area pacing over His-bundle pacing because the former “offers the benefits of physiologic pacing with higher implant success rates and stable long-term lead parameters.”

We need to find out how much of a clinical benefit there is with [conduction-system] pacing compared with classic pacing in a TAVR patient. Christopher Meduri

Christopher Meduri, MD (Piedmont Heart Institute, Atlanta, GA), who wasn’t involved in the study, said the risks of cardiomyopathy and heart failure resulting from RV pacing for AV block after TAVR are relatively small in older patients with a shorter life span, but that there is a potential need to make sure pacing doesn’t lead to dyssynchrony and associated complications “10, 15, or 20 years down the road.”  

“I think it’s great we’re thinking about more-effective ways to treat patients who require a pacemaker after TAVR, but I think this is more a proof-of-concept study showing that you can effectively place one of these types of pacemakers, more so with left bundle branch pacing, which was pretty successful,” he said. “We need to find out how much of a clinical benefit there is with [conduction-system] pacing compared with classic pacing in a TAVR patient. From what I understand, there isn’t a lot of randomized, controlled evidence for this versus biventricular pacing. They’ll still need to prove how much of a benefit there is with pacing this way, but the theory does seem to fit.”

If this proves to be an advantage, there will be future questions about which particular patient derives the most benefit from conduction-system pacing as opposed to RV or biventricular pacing. Cost, Meduri added, is also a potential issue, noting that with any technical advance, the price of the procedure tends to rise.

Need for Longer Follow-up

To TCTMD, Vijayaraman said the study is relatively short at 12 months and that further follow-up is needed to determine the impact of conduction-system pacing on LVEF and heart failure-related deaths and hospitalizations. “We need long-term studies, and possibly a randomized study, to show that we’re not exchanging one problem for another problem,” he said.

At their center, when TAVR was relatively new, they were hesitant of pacing the His-Purkinje system in patients with heart block. It can be technically challenging, mainly because accessing the His bundle can be difficult from the right side of the heart, said Vijayaraman. “With the combination of the His bundle or left bundle branch [area] pacing, we were able to get below the site where TAVR creates the block and get to the conduction system much more consistently,” he said.

Conduction-system pacing is slowly being adopted by more and more electrophysiologists, but there is little industry support behind it, added Vijayaraman.

“For the last few years, there’s been a rapid uptake of this technique,” he commented. “We have trained even nonelectrophysiologist implanters to do this. His-bundle pacing, unfortunately, is mainly an [electrophysiology]-type of procedure, but left bundle branch pacing may be more democratized in the sense that any good implanter can learn to do it.” He added that His bundle and left bundle branch area pacing actually has some advantages in TAVR because the valve struts serve as a fluoroscopic marker for identifying the His bundle region.