Long-term hemodynamic assessment of the porcine heterograft in the mitral position. Late development of valvular stenosis.

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Abstract
We undertook a study of patients who had porcine mitral valves in place for more than 5 years and who had no clinical signs or symptoms suggestive of valve dysfunction. Of the first 54 patients who had porcine valves implanted in the mitral position, 18 were available for catheterization; all had a routine hemodynamic study postoperatively (mean 7 months) for comparison. Mean follow-up was 85 months (range 61-111 months). Compared with the early postoperative data, there was a significant increase in mean mitral valve gradient, from 5.9 +/- 0.7 to 8.6 +/- 0.7 mm Hg (p less than 0.01), and a significant decrease in calculated mitral valve area, from 2.2 +/- 0.2 to 1.7 +/- 0.2 cm2 (p less than 0.01). Moreover, seven patients showed a decrease in valve area greater than 1.0 cm2, five with valves in place for more than 80 months and only two of 11 patients with valves in place for 80 months or less (p less than 0.05). We conclude that there is a significant incidence of hemodynamic deterioration of porcine heterografts in the mitral position for greater than 5 years, even in patients who are clinically stable.