Leadless Pacemaker Implant Location as a Predictor of Pacing Induced Cardiomyopathy

Leadless pacemakers (LPs) avoid the lead- and pocket-related complications of transvenous systems, but they pace exclusively from the right ventricle (RV), and chronic RV pacing carries a recognized risk of pacing-induced cardiomyopathy (PICM). Whether implant location within the RV, a potentially modifiable factor, contributes to this risk has not been established.

Patients undergoing LP implantation with ≥50% RV pacing, pre-and post-procedural echocardiograms, and post-implant 3-dimensional radiographic imaging were included. All implants targeted the RV septum per manufacturer recommendation. PICM was defined as ≥10% decline in left ventricular ejection fraction (LVEF) to <50% without alternative cause.

PICM developed in 20/81 patients (24.7%), with LVEF declining from 61±8% to 37±9%. Post-implant 3-dimensional radiographic imaging demonstrated inadvertent free wall implantation in 15/20 patients who developed PICM (75%) compared with 8/61 patients who did not (13%; P <0.001). Paced QRS duration was wider in patients with PICM than in those without (186±19 vs 155±13 ms, P <0.001) and discriminated free wall from non-free wall implantation with an area under the receiver operating characteristic curve (AUC) of 0.85; a QRS duration of 172 ms provided optimal discrimination. Baseline LVEF, baseline QRS duration, and comorbidity burden did not differ between groups.

Inadvertent free wall LP implantation is strongly associated with the subsequent development of PICM. Paced QRS duration is a readily available surrogate for implant location, and targeting a paced QRS duration below approximately 172 ms at the time of implant may serve as a practical, non-invasive check on appropriate septal placement.