(P005) EFFECTS OF ENVELOPES ON CIED POCKET HEALING: A HEAD-TO-HEAD PRECLINICAL EVALUATION

Background:

Background: The body’s immune response to cardiac implantable electronic device (CIED) implantation results in capsule formation with healthy surrounding tissue. Alternatively, chronic inflammation and infection can disrupt healing, cause pocket instability, and increase morbidity. Two envelopes are currently available to provide CIED stabilization: the TYRX absorbable antibacterial envelope and the CanGaroo envelope derived from porcine extracellular matrix (ECM). Effects of these envelopes on CIED pocket healing are not well-known.

Purpose: To compare effects of TYRX, ECM, and no envelope on pocket healing.

METHODS AND RESULTS: Eighteen sheep were used in a time-course study (3d, 7d, 4wks, 12wks post-implant) of pocket healing. Across all animals, CIEDs were implanted with TYRX (n=16) or ECM envelopes (n=14) per manufacturer’s instructions, or no envelope (control=20). At least one control was implanted in each animal. Envelope types were rotated to eliminate the potential effect of implant location on healing. Peridevice tissue findings were assessed by an independent pathologist via blinded histopathological analyses for parameters included in ISO 10993-6:2016. For capsule thickness comparisons, a mixed-effects model with a random subject (sheep) effect and fixed-time and treatment effects was applied. The TYRX inflammatory response was low, as indicated by scoring for neutrophils, fibrin, and macrophages (Figure 1A). Neutrophil scores for TYRX and control declined from moderate (score ≤2) at 3d to absent (score=0) at 4wks and 12wks, whereas ECM scoring for neutrophils showed an elevated response at 3d (score=3.2) and 7d (score=2.2). Less fibrin deposition was observed with TYRX at 3d (score=0.8) compared to control (score=1.6) and ECM (score=2.0). Macrophage scoring was slightly lower at 7d for TYRX (score=2.2) compared to ECM (score=2.8) or control (score=3.0). Rapid tissue repair with TYRX was evidenced by increased fibrosis at 7d (score=1.8) compared to control (score=1.0) or ECM (score=0.6). Granulation tissue had developed by 7d in all pockets but decreased only for control (score=0.6) and TYRX (score=1.0) at 28d while ECM was barely reduced (score=2.0). Degree of neovascularization ≥ 7d was similar for all pockets. Capsule thickness peaked at 4wks for all groups and ECM capsular thickness was significantly increased compared to TYRX and control (p < 0.01, Figure 1B). There was no evidence of fat infiltration or calcification.

Conclusion:

Conclusion: The TYRX absorbable antibacterial envelope was associated with a more rapid natural healing response with less inflammation and thin uniform capsule formation compared to ECM. These healing conditions can foster development of a well-healed pocket that may ease secondary procedures when required.