Another BiV Pacing Alternative? Acute LV-Septal Pacing Enticing for CRT in Small Study

February 05, 2020

Although His-bundle pacing (HBP) has been gaining ground as an alternative to standard biventricular (BiV) pacing for cardiac resynchronization therapy (CRT) in heart failure, and may offer some advantages, other contenders are on the horizon.

One of those is left ventricular septal (LVs) pacing, which rivaled HBP and BiV pacing in a small "proof of principle" study that compared their acute hemodynamic and electrophysiologic effects in patients with guideline-based indications for CRT.

Left ventricular septal pacing in the study was associated with short-term hemodynamic improvement and "electrical resynchronization" that was "at least as good" as those achieved with the other two pacing techniques, lead author Floor C.W.M. Salden, Maastricht University, the Netherlands, told | Medscape Cardiology.

It achieved better resynchronization than BiV pacing, and performance was similar to HBP on two electrophysiologic measures while essentially matching both for boosting hemodynamics, according to the study, published January 27 in the Journal of the American College of Cardiology.

Both LVs and HBP rely on a single ventricular endocardial lead, which could be an advantage over BiV pacing, with its two ventricular leads and one atrial lead; most serious complications of pacemaker therapy involve the lead systems.

"If these acute electrophysiological and hemodynamic improvements achieved with LVs pacing can reliably predict clinical and echocardiographic response, then it is early evidence that LVs pacing may be a reasonable alternative for CRT," an accompanying editorial proposes.

Its authors, led by Pugazhendhi Vijayaraman, MD, Geisinger Heart Institute, Wilkes-Barre, Pennsylvania, also touted the potential benefits of another single-lead pacing technique that could potentially rival BiV pacing in CRT.

Left-bundle-branch pacing (LBBP), they write, "offers the ability to not only pace the LV septal endocardium, but also stimulate the left bundle branch, allowing for rapid activation of the LV myocardium."

Although LVs pacing performed at least comparably to BiV pacing acutely in the current study, the editorialists note, whether it can compete with BiV for clinical benefit has yet to be seen. Therefore, "in patients requiring CRT who fail transvenous LV lead placement, or BiV nonresponders, His-Purkinje conduction system pacing (HBP or LBBP) would provide an excellent alternative."

Importantly in the current study, LVs pacing similarly benefited electrophysiologic and hemodynamic measures regardless of pacing site, whether the LV basal septum or the mid or apical septum.

"Our study shows that the position of the LV septal electrode is not critical, suggesting that LV septal lead implantation is easier than His bundle and left bundle branch area pacing," Salden said.

His-bundle pacing electrodes must be precisely positioned, he observed, a process that "requires electrical mapping of the His bundle, leading to a long learning curve." Other disadvantages of HBP include "sensing issues and higher capture thresholds (especially in the setting of a bundle branch block), and rising thresholds, leading to an increased risk for lead revisions."

Also, LVs pacing "provides a more physiological activation than BiV pacing, as activation occurs from LV endocardium to epicardium," Salden said. In BiV pacing, the LV lead is entirely transvenous.

"Therefore, LVs pacing seems easier and more widely applicable than His bundle pacing." Also, it is "at least an alternative to BiV pacing and, moreover, seems easier to apply than BiV pacing."

In the prospective two-center study, 27 predominantly male patients slated for standard BiV CRT, about half of whom had ischemic cardiomyopathy, underwent temporary LVs and BiV pacing studies, which included transcatheter pressure readings and multielectrode body surface mapping. The cohort included a subgroup of 16 patients who were also tested during HBP.

Their mean QRS area went from 116 mV at baseline to 73 mV during LVs pacing, but only to 93 mV at BiV pacing. Their mean standard deviation of activation times (SDAT) went from 36 ms at baseline to 26 ms at LVs pacing, but to 39 ms with BiV pacing. For both parameters, which reflect ventricular synchronicity, the difference between the LVs and BiV pacing response was significant (P < .05).

In contrast, QRS area and SDAT improved to about the same degree during LVs pacing and HBP.

The maximum rate of LV pressure rise (LVdP/dtmax) during systole, which reflects contractility, the report notes, averaged 823 mm Hg/s at baseline and rose to similar degrees — 17% to 20% — during the three different pacing modes.

As described by Salden, LVs pacing leads are currently implanted by passing them transvenously into the right ventricle to a position against the right ventricular septum. The lead tip is then screwed into the septum until it reaches the endocardial layer just short of the left ventricular chamber.

"This approach avoids access of the LV lead into the LV cavity, and so there is no need for anticoagulation."

The study was partly supported by Medtronic. Salden reports that he has no relevant conflicts; disclosures for the other authors are in the report. Vijayaraman discloses receiving fellowship and research support from and has served as a speaker and/or consultant for Medtronic; and serving on advisory boards for Boston Scientific, Biotronik, Abbott, and Eaglepoint. Disclosures for the other editorialists are in their publication.

J Am Coll Cardiol. January 27, 2020. Abstract, Editorial

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