Blood Flow in the Foreign-Body Capsules Surrounding Surgically Implanted Subcutaneous Devices

BackgroundSurgically implanted devices initiate inflammatory mechanisms and wound healing events and result in the formation of a thick fibrotic capsule that surrounds the device. To investigate the foreign-body response to devices of clinically relevant size, we used microspheres to determine regional blood flow patterns in the foreign-body capsule (FBC) and surrounding subcutaneous tissue after device implantation.Materials and MethodsIn 10 canines, we implanted 40 subcutaneous devices (polysulfone n = 20, silicone-coated n = 10, titanium n = 10). Via thoracotomy, animals were instrumented with left atrial and aortic vascular access catheters for serial microsphere injections and reference blood sampling. Regional blood flow was repeatedly determined in the FBC, subcutaneous fascia surrounding the FBC, and subcutaneous fascia distal to the surgical site up to 19 wk after device implantation (n = 55 determinations).ResultsCompared with normal blood flow in subcutaneous fascia distal to the surgical site, blood flow increased in FBCs surrounding each device material (polysulfone P = 0.0035, silicone-coated P < 0.0001, titanium P < 0.0001). Additionally, blood flow increased in the subcutaneous fascia within half a centimeter of fibrous capsules encasing polysulfone (P = 0.0081) but not silicone (P = 0.3706) or titanium (P = 0.8160) devices. The time-course of measured blood flow changes within FBCs were similar for polysulfone and silicone but not for titanium.ConclusionsSurgically implanted subcutaneous devices of clinically relevant size elicit increases in blood flow in the FBC as well as surrounding fascia. Device material may influence regional blood flow patterns.