Morphometric parameters of cardiac implantable electronic device (CIED) pocket walls observed on device replacement.
The final stage of a conventional de-novo cardiac implantable electronic device (CIED) implantation procedure with transvenous lead insertion involves the formation of a pocket by tissue separation superficial to the pectoralis major muscle in the right or left infraclavicular region, where the device is subsequently placed. Over time, a scar "capsule" forms around the CIED as a result of normal biological remodeling. The purpose of this study was to analyze the structure and present the variations of CIED capsules observed during device replacement. The nature and extent of this local tissue remodeling, which had occurred from the time of device implantation to its replacement in 2016 (10 ±3.1 years), was analyzed in 100 patients (mean age 77.1±14.5 years), including 45 women and 55 men. The largest type of "capsules" (70% of cases) were those with similar thickness of both walls or a slightly thicker posterior (<1.0mm) than anterior wall (<0.5mm). The second most common capsule type (23% of cases) was characterized by a significantly thicker posterior wall of scar tissue (˃1.0mm). The third group of capsules was characterized by various degrees of wall calcification (7% of cases). The extent and nature of scar tissue structure in the CIED pocket walls seems to correlate with the relative position of cardiac lead loops with respect to the device itself; where the more extensive scarring likely resulting from pocket wall irritation in the capsule formation phase due to lead movements underneath the device. The group of cases with calcified capsules was characterized by "old" device pockets (˃ 13 years) and the oldest population (patients in their 80s and 90s).