Reduced fibrous capsule elastic fibers of biologic ECM-enveloped CIEDs in minipigs fitted with a compression mechanics model
BACKGROUNDFibrous 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 partially to their increased compressive strength, previously linked to elevated tissue fibers. OBJECTIVETo quantify structural proteins, determine if biologic extracellular matrix-enveloped CIEDs (PECM) caused differential Fb properties, and to implement a realistic mechanical model. METHODSRetrieved Fb (-P and -PECM) from minipigs were subjected to biomechanical (shear oscillation and uniaxial compression) and histological (collagen I and elastin) analyses. RESULTSFb-PECM showed significant decreases compared to Fb-P in: 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 g/mg tissue). Decreases in elastin were particularly noted closer to the implants surface (Fb-PECM = 71% vs. Fb-P = 143% relative to dermal elastin at mid-tangential sections) and verified with a solid mechanics hyperelasticity with direction-dependent fiber viscoelasticity compression simulation (r2 [≥] 98.9%). CONCLUSIONSThe biologic envelope composed of decellularized porcine small intestine submucosa ECM for CIEDs promoted fibrous tissues with less elastic fibers. Novel compression modeling analyses directly correlated this singular reduction to more desirable subcutaneous tissue mechanics.