Investigation of non-physiological calcification in artificial organs after implantation ; OPN and macrophages

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Healing characteristics of small-caliber vascular prostheses used in small children have rarely been observed because removing specimens are troublesome. Modified Blalock Taussig shunt procedures were performed using small caliber expanded polytetrafluoroethylene (ePTFE) vascular grafts and fabric grafts in 13 patients with congenital heart disease. At the time of total corrective procedures, a piece of 10 ePTFE grafts in 10 patients and six fabric grafts in four patients were removed from the distal pulmonary anastomosis, and evaluated. The implantation duration was from 11 months to 5 years and 7 months (mean, 2 years and 6 months). At removal, average patient age was 4 years and all grafts were patent. Microscopically, the wall of three ePTFE grafts were calcified, and macrophages were immunohistologically observed in the graft wall. Thrombus formation, intimal hyperplasia, and pannus detachment was common. In the fabric grafts, many capillaries infiltrated the interstices and often reached the lumen from the perigraft side. These results suggested that in cyanotic small children, angiogenesis in and around fabric grafts was active and calcification was accelerated in ePTFE grafts. Complete endothelialization throughout the length, caused by angiogenesis, might be possible in small children when highly porous fabric vascular prostheses are used.