DIAGNOSTIC METHODS VALVE REPLACEMENT Chemically determined mineral content of explanted porcine aortic valve bioprostheses: correlation with radiographic assessment of calcification and clinical data

Bioprosthetic valve calcification is usually assessed pathologically by gross inspection, radiographic studies, and histologic examination. Quantitation of mineral content by chemical assay has not been reported for failed clinical valves removed from adults. In this study, calcium determination by atomic absorption spectroscopy was done on 52 removed porcine valves after routine pathologic examination, including specimen radiography done by a standard technique. Specimens included 31 valves with calcific primary tissue failure, two calcified (but not overtly dysfunctional) valves removed simultaneously with failed valves, 14 nondeteriorated valves obtained at reoperation or autopsy after long-term implantation, and five valves removed within 1 month after insertion. Chemically determined mineral content varied widely among patients and duration of function. Valves with calcific failure had 113 + 68 gg/mg calcium overall (mean ± SD) after 36 to 156 months (mean 87) of function. Almost all dysfunctional porcine valves with radiographically demonstrated calcific deposits had greater than 34 and 67 ,ug/mg calcium for mitral and aortic valves, respectively. Nondeteriorated valves (implanted 8 to 145 months, mean 57) had 5 + 6 gg/mg calcium. Failed aortic valves had more calcium than failed mitral valves and valves with calcific stenosis more than valves with regurgitation caused by calcification with tearing. Correlation of semiquantitative radiographic grading with chemically determined valve mineral was good, indicating that radiographic assessment of calcification may be used reliably for clinical comparisons between valves. Circulation 76, No. 5, 1061-1066, 1987. BIOPROSTHESES fabricated from glutaraldehydepreserved porcine aortic valve or bovine pericardium are widely used to replace diseased human cardiac valves. Clinical regurgitation, stenosis, or both are frequently caused by primary tissue failure, necessitating reoperation with valve removal or causing death of approximately 25% of patients with porcine bioprostheses within 10 years after insertion. 1-5 Calcification, with or without secondary cuspal tearing, is the most prominent pathologic factor. 1 2 Pericardial bioprostheses also fail by calcific degeneration.i8 Assessment of calcification in explanted bioprosFrom the Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston; and Division of Cardiology, Departments of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor. Supported in part by grants HL38118 and HL36574 from the NIH. Address for correspondence: Frederick J. Schoen, M.D., Ph.D., Department of Pathology, Brigham and Women's Hospital, 75 Francis St., Boston, MA 02115. Received July 7, 1987; accepted July 30, 1987. thetic valve specimens is usually done by gross inspection, histologic examination, and radiographic studies.9-'1 Quantitative mineral determinations by chemical assay of accumulated calcium and phosphorus have been used widely in experimental studies'2-'5 and have been reported for a limited number of valves removed from children,2 but such data are not available for failed valves explanted from adults. The purposes of this study were to quantitatively determine mineral accumulation in removed dysfunctional and properly functioning porcine bioprostheses by chemical assay and to correlate these data with semiquantitative, nondestructive radiographic assessment of calcification and selected clinical variables. Materials and methods Fifty-two glutaraldehyde-preserved porcine aortic valve bioprostheses were studied. These valves were removed from adults over an interval of approximately 5 years, fixed, and stored in 10% neutral phosphate-buffered formalin. Fourteen nondeteriorated valves (six aortic and eight mitral, including 12 Hancock Vol. 76, No. 5, November 1987 1061 by gest on A ril 7, 2017 http://ciajournals.org/ D ow nladed from