Calcification of porcine prosthetic heart valves: a radiographic and light microscopy study

To determine the incidence and extent of calcification of implanted glutaraldehyde-treated porcine prosthetic heart valves, 82 valves explanted from 73 patients were examined for calcium by radiography and light microscopy. At the time of valve implantation, the patients were 2 1/4-76 years old. The included 15 children (patients younger than 15 years of age, mean age at time of valve implantation 8.7 +/- 4.1 years) and 58 adults (patients older than 15 years, mean age at time of valve implantation 53.5 +/- 15.1 years). Valves explanted from children (average time implanted 4.6 +/- 1.7 years) included four aortic, five mitral, as well as six right ventricle-pulmonary artery conduits and one left ventricle-abdominal aorta conduit. Valves explanted from adults (average time implanted 3.2 +/- 2.5 years) included 32 aortic and 32 mitral, as well as one tricuspid valve and one valve from a right ventricle-pulmonary artery conduit. Calcification of explanted valves was graded from 0 to 4+ based on radiographs. All 16 valves from children were calcified, with grade 3+ or 4+ calcification in each of the aortic and mitral valves. In adult patients, calcification was present in 10 of 33 valves (30%) implanted for less than 3 years (average time implanted 1.0 year), in nine of 11 valves (82%) implanted for 3-5 years (average time implanted 3.7 years) and in 21 of 22 valves (96%) implanted for 5 years or longer (average time implanted 6.2 years). Analysis of variance demonstrated that calcification was strongly related to the duration that valves were implanted (p less than 0.001). Age at the time of valve implantation also had a strong effect (p less than 0.001) on the amount of valvular calcium. Valves from children showed the most calcification, and the amount did not change when valves were implanted in patients 30 years of age or older. Patient sex and valve position had no effect on the amount of calcification. Calcification occurred at each right- and left-heart valve position, most frequently at sites of commissural attachments.