Use of Hancock porcine xenografts in children and adolescents

Between January 1,1974 and December 31,1978,47 xenografts (8 aortic, 28 mitral, 4 tricuspid, 3 left atrioventricular valve in I-transposition of the great arteries and 3 aortic-mitral) were implanted in 44 patients, aged 10/12 to 20 5/12 years (median 12 2/12). All eight patients with aortic valve replacement survived and were followed up for 22.5 ± 10.4 months (mean ± standard error of the mean). At postoperative cardiac catheterization in three patients, the peak systolic ejection gradient ranged between 24 and 38 mm Hg and the valve area index between 0.71 and 1.15 cm²/m². Among 26 patients who underwent mitral valve replacement, 5 died operatively and 2 died 2 months postoperatively, leaving 19 long-term survivors who were followed up for 26.2 ± 15.6 months. In the 11 patients who underwent postoperative cardiac catheterization, the mean diastolic gradient was 6.1 ± 2.7 mm Hg and the mean valve index 1.79 ± 0.76 cm²/m². Severe subaortic obstruction, due to the prosthetic mitral valve, occurred in three of five patients less than 5 years old.Among four patients who underwent tricuspid valve replacement there were no operative deaths; complete heart block occurred in three. At postoperative catheterization in two patients, the mean diastolic gradient was 3 and 5 mm Hg, and the valve index 1.32 and 1.7 cm²/m², respectively. Three patients with I-transposition of the great arteries who underwent replacement of the systemic atrioventricular valve were followed up for 12 to 37 months. At postoperative catheterization the mean diastolic gradient was 0 to 4 mm Hg and the valve index ranged from 1.68 to 1.88 cm²/m². Both aortic and mitral valves were replaced in three children. One died at operation and one 6 months after operation. The survivor has complete heart block but is in New York Heart Association functional class I.Eight xenografts (6 mitral, 1 left atrioventricular valve in I-transposition of the great arteries and 1 aortic) failed, requiring replacement 22 to 68 months after implantation. All were calcified to varying degrees. Valve failure began presenting 22 months after implantation, and of 25 valves implanted for 20 months or longer, 8 have been replaced. These 8 patients were younger (10.3 ± 0.2 years) at initial valve replacement than the other 17 patients (15.0 ± 0.3 years) followed up for 20 months or longer (p <0.05). High levels of γ-carboxyglutamic acid (GLA), a calciumbinding amino acid, were found in all six calcified xenografts analyzed, whereas none was found in a fresh porcine aortic valve or in an unimplanted xenograft. GLA-containing protein, laid down after implantation, may play a role in xenograft calcification.