Centers considering or currently employing collagen seals similar to the device described here should find this histopathologic evaluation of arteriotomy wound healing reassuring, as this study demonstrates similar healing for both collagen device treated and manually compressed wounds. These experiments demonstrate healing after use of a collagen plug is not associated with a granulation tissue response (evidenced by a lack of giant cells), but they suggest pressure and/or trauma-induced fat necrosis of the subcutaneous fat-pad is seen in both and may play a role in the healing process. The absence of granuloma suggests the collagen device described acts as a relatively inert seal and causes no foreign body reaction, at least in this pig model.

The identification of fat necrosis in both types of closure would not surprise any who have witnessed a sheath removal. It has long been my supposition that in manual groin compression there is a component of additional tissue trauma, which elaborates more Tissue Factor, which in turn facilitates coagulation and hemostasis. This may explain why many feel a ham-fisted orderly does a better job of achieving hemostasis than the less traumatic firm and steady application of a C-clamp. The presence of fat necrosis in both collagen plug treated and manually compressed wounds suggests the amount of trauma induced by the device, manual compression, or caused by the percutaneous insertion of the arteriotomy needle is sufficient to cause at least some damage to fat cells. The amount of trauma necessary to induce fat necrosis may simply be less than the authors suppose. Alternatively, the subsequent inflammatory reaction in the healing tract may result in secondary lipocyte injury and death or apoptosis. By animal sacrifice at 30 days, it may no longer be possible to determine the exact cause of the fat necrosis.

The finding that manual compressed and collagen plug sealed wounds appear similar at 30 days suggests these wounds should behave similarly both early and late. This lends further evidence that the type of closure (collagen plug or manual compression) employed has little bearing on how the patient should be approached for subsequent access. The amount of subcutaneous fibrosis and suitability of the site for re-access should be similar.