The Toronto SPV bioprosthesis: review of morphological findings in eight valves

The morphological findings in eight explanted Toronto SPV bioprostheses were described. Clinical records were reviewed for patient information and data regarding the explanted bioprosthesis, all of which were analyzed in detail by gross and histological examination. All valves were also examined radiologically and detailed specimen photographs obtained. When warranted, tissue cultures were taken and special stains for microorganisms obtained. The Toronto SPV bioprosthesis has been used for aortic valve replacement in 270 patients since its introduction in 1991. The follow-up evaluation was 99.5% complete. Eight valves have been explanted: three at surgery and five at autopsy. Patient age ranged from 35 to 69 years, with five male and three female patients. Indications for aortic valve replacement were aortic stenosis in all cases. Implant duration ranged from 5 weeks to just over 6 years (mean 38 months). Early failures (2) were due to infective endocarditis. Two patients died of acute myocardial infarction, related to pre-existing coronary artery disease, and two died from lung cancer. All late explants showed host tissue growth (grade 2-3), with variable extension onto both the proximal and distal suture lines, as well as extension onto the cusps and commissures on the flow and nonflow surfaces. Extension of pannus onto native aortic tissues was seen but did not encroach on the coronary ostia. Tissue degenerative changes were present, as were small tears (type 1) in two valves. Mild calcification was seen in two valves. The Toronto SPV has excellent clinical performance at up to 8 years of follow-up evaluation. In this series, early failures are related to infective endocarditis, and later explants (6 of 8) are associated with mild tissue degeneration and an occasional cusp tear. At up to 5 years, only minimal/mild calcification was seen in two of the eight valves.