Evaluation of cyropreserved internal thoracic artery as an alternative coronary graft: evidence for preserved functional, metabolic and structural integrity.

The internal thoracic artery (ITA) is the conduit of choice for coronary artery bypass grafting (CABG). This study, utilizing a canine model, evaluates cryopreserved ITA. Sixteen ITAs were harvested and cryopreserved according to United CryoInstitute protocol. Test conduits, 5 cm long and 4 mm mean diameter, were anastomosed to the ligated carotid artery of an unmatched mongrel recipient, above and below the site of native artery ligation. Graft patency was assessed by angiography at 14 days (early) and 980 days (late) postoperatively. Catheterization of the 16 vessels identified three (18%) early and one (6%) late graft occlusion. Ninety days postoperatively, each dog was killed and the graft harvested for histopathological and functional evaluation. Morphologic evaluation, using conventional staining, showed preserved cellular structure, decrease in smooth muscle cells and distorted endothelial layer. Immunocytochemistry, using an antibody against prostacyclin (PGI2), detected PGI2 immunoactivity in the ITA smooth muscle cells. An in vitro assay performed on the arterial rings confirmed preserved functional integrity of the vascular endothelium and smooth muscle. These findings suggest that cryopreserved ITA may have potential as a substitute graft, in devising conduit strategies for primary or reoperative coronary bypass surgery.

Efficacy of autologous peritoneum as a biological membrane in cardiac surgery.

The risks for reoperative cardiac surgery are related to the presence of intrapericardial adhesions and the possibility of catastrophic injury at repeat sternotomy. In an attempt to develop an improved pericardial substitute and vascular patch, the feasibility of using autologous peritoneum was evaluated. Twelve mongrel dogs were studied. A peritoneal-rectus fascia patch, including the overlying posterior rectus sheath was harvested, via a lateral abdominal incision, and stored in normal saline. In the first group of six animals, a pulmonary artery (PA) window was created and then closed with the peritoneal-rectus fascia patch. In the second group a secundum atrial septal defect was created and then closed with the peritoneal patch on cardiopulmonary bypass (CPB). In each animal, the peritoneal-rectus fascia patch was used to permit pericardial closure. Autopsies performed at 90 days postoperatively revealed only slight intrapericardial adhesion formation and a mild epicardial reaction. Histological examination of the peritoneal-rectus fascia patches revealed intact morphology with active fibroblasts and smooth muscle cells. Proline 14C absorption and autoradiography detected viable cells in the implanted patches. These findings suggest that a peritoneal-rectus fascia allograft could be useful as a biological membrane, and as a satisfactory pericardial substitute in the development of strategies to reduce the risk for reoperative cardiac surgery.