Frequency and Extent of Leadless Pacemaker Encapsulation

Leadless pacemakers (LPs) are increasingly used for permanent pacing. Although infrequent, retrieval of chronic implants may be necessary but are hindered by encapsulation and tissue adherence. To date, LP encapsulation has been described only in animal models and postmortem specimens.

The objective of this study was to assess the presence, extent, and anatomical characteristics of LP encapsulation using contrast-enhanced computed tomography (CT).

We conducted a retrospective study of all patients with LPs implanted at our center who underwent postimplantation contrast-enhanced thoracic CT imaging. CT images were independently reviewed by cardiothoracic radiologists using a standardized protocol to assess encapsulation severity, tissue origin, interaction with the retrieval feature, tine myocardial penetration, and device motion.

Among 742 patients with LPs implanted at our center, 69 underwent postimplantation CT. Of these patients, 59 patients had images in which encapsulation could be assessed. The CT images (mean time from implantation: 863 ± 669 days) demonstrated some degree of LP encapsulation in 50 (85%) patients; 18 (31%) had moderate or extensive encapsulation, and 2 (3%) had complete encasement. Encapsulation tissue originated from the myocardium (36%) and/or trabeculations/subvalvular apparatus (83%). In 16 (27%) patients, tissue involved the LP retrieval feature. Of 13 patients with serial imaging, 3 demonstrated progressive encapsulation. Transmural tine penetration was observed in 7 (12%) patients, and right ventricular free wall implantation was observed in 18 (26%) patients. CT revealed potential anatomic retrieval barriers in 36 (61%) patients.

CT imaging can visualize in vivo LP encapsulation that is common, varies in severity, and can involve multiple anatomical structures. Therefore, CT imaging may identify potential retrieval challenges, informing risk stratification and procedural strategy.