Reduced fibrous capsule elastic fibers from biologic ECM-enveloped CIEDs in minipigs, supported with a novel compression mechanics model

Abstract

BACKGROUND: Fibrous capsules (Fb) in response to cardiovascular implantable electronic devices (CIEDs) including a pacemaker (P) system, can produce patient discomfort and difficulties in revision surgery due to their high compressive strength, potentially via elevated elastic fibers. OBJECTIVE: To determine if biologic extracellular matrix-enveloped CIEDs (PECM) caused differential Fb properties. METHODS: Retrieved Fb (-P and -PECM) from minipigs were subjected to biomechanical (shear oscillation and uniaxial compression) and histological (collagen I and elastin) analyzes. RESULTS: Fb-PECM showed significant decreases compared to Fb-P at: low strain-loss modulus (390 vs. 541 Pa) across angular frequencies, high strain-compressive elastic modulus (1043 vs. 2042 kPa), and elastic fiber content (1.92 vs. 3.15 μg/mg tissue), particularly closer to the implant's surface (71% vs. 143% relative to skin dermis elastin) and verified with a solid mechanics hyperelasticity with direction-dependent fiber viscoelasticity compression simulation (r2 ≥ 98.9%). CONCLUSIONS: The biocompatible wrap composed of decellularized porcine ECM for CIEDs generated fibrous tissues with less elastic fibers which contributed to a more desirable material mechanics.