A juvenile sheep model for the long-term evaluation of stentless bioprostheses implanted as aortic root replacements.

BACKGROUND AND AIM OF THE STUDY: Orthotopic valve replacement in large animals is an important component of the preclinical assessment of bioprosthetic valves. To provide the most useful preclinical information, the development of models that parallel clinical practice patterns is essential. Therefore, we sought to develop a technically feasible and reproducible model for chronic evaluation of stentless bioprosthetic aortic valves implanted as aortic root replacements in juvenile sheep. METHODS: Juvenile domestic sheep (mean age 21+/-2.28 weeks; range: 17-26 weeks) underwent aortic root replacement using standard cardiopulmonary bypass (CPB) and surgical techniques. Animals were implanted with 19 mm (n = 21), 21 mm (n = 18) or 23 mm (n = 4) bioprostheses from two different manufacturers, and followed for 150 days. Animals surviving at least 150 days were considered long-term survivors; those which died prior to postoperative day (POD) 31 were considered operative deaths. RESULTS: Forty-three animals underwent aortic root replacement. The mean CPB time was 91+/-20 min (range: 62-149 min); mean cross-clamp time was 63+/-13 min (range: 39-95 min). Thirty-five animals (81%) survived the first 30 days of the study period. Five deaths occurred at POD 0 due to anastomotic complications. One death occurred each on POD 3, 6, and 26 as a result of prosthesis size mismatching, thromboembolic complications, and endocarditis, respectively. There were five late deaths. Twenty animals survived the minimum 150-day study period, and 12 were sacrificed at 183+/-17 days. Six animals remain alive at 151+/-0.98 days, and one animal died each on POD 184 and 190. The remaining 10 animals are not yet 150 days from their operation. Currently, all are well at 102+/-34 days (range: 33-140) days. CONCLUSION: These data suggest that long-term evaluation of stentless aortic bioprostheses implanted as aortic root replacements can be accomplished using juvenile sheep.

Red-cell uroporphyrinogen decarboxylase activity in porphyria cutanea tarda and in other forms of porphyria.

To test the diagnostic specificity of reduced red-cell uroporphyrinogen decarboxylase activity for porphyria cutanea tarda, we measured enzymic activity in 29 normal subjects and 65 patients with various forms of porphyria. Only patients with porphyria cutanea tarda had subnormal enzymic activity. Patients with acute intermittent porphyria, erythropoietic protoporphyria, variegate porphyria and hereditary coproporphyria had normal or slightly elevated activities. The enzymic activity in normal persons and patients with porphyria cutanea tarda did not differ according to sex. Reduction of iron stores did not alter the enzymic activity in porphyria cutanea tarda. We conclude that reduced red-cell uroporphyrinogen decarboxylase activity is a specific and intrinsic defect in porphyria cutanea tarda; measurement of this enzyme is a reliable diagnostic test for this disease.