Strategies for biological heart valve replacement: Stentless xenografts fail to evolve into an alternative pulmonary valve substitute in a Ross procedure

Abstract

The Ross operation is a complex procedure for aortic valve replacement in which the pulmonary autograft is replaced by a homograft. However, homograft availability is becoming limited. This report evaluates the performance of porcine stentless prostheses as alternative pulmonary substitutes. Echocardiographic results from two patient cohorts were compared at time of discharge and 1 year after a Ross procedure. Thirty-three patients (median age 42 years, range 17-62 years, 76% male) received a stentless prosthesis (median size 25.6 mm, range 25-29 mm) for right ventricular outflow tract reconstruction. Clinical data were not significantly different from 106 patients (median age 47 years, range 2-68 years, 75% male) who received cryopreserved homografts (median size 26 mm, range 20-33 mm). At time of discharge, peak pressure gradients (ΔPmax ) across the stentless valve (median ΔPmax 13 mmHg, range 2-26 mmHg) were higher compared to homografts (median ΔPmax 7 mmHg, range 1-32 mmHg, p<0.001). At 1 year, gradients increased in both groups, but were significantly higher across stentless valves (median ΔPmax 23 mmHg, range 10-81 mmHg vs. median ΔPmax 13 mmHg, range 2-74 mmHg, p<0.001). Eleven patients (33%) in the stentless-valve group were classified "at risk" with a ΔPmax of ≥30 mmHg. Four of them (12%) had to be re-operated. In conclusion, stentless valves showed higher pressure gradients and their performance was inferior to cryopreserved homografts. See accompanying commentary by Ulrich Stock DOI: 10.1002/biot.201200341.

Searching for the optimal heart valve

“…There is substantiated hope that this will benefit patients in need of heart valve transplantation. Weimar and colleagues [1] are to be congratulated for their honest results highlighting the continuing limitations and need to search for the optimal valve for pediatric and young adult patients.…”

“…Allografts have optimal hemodynamic characteristics and are resistant to infections. Disadvantages of allografts, particularly in pediatric and young adult patients (the group presented by Weimar et al [1]), include its limited availability (due to decreasing organ donations), an inability to grow, degeneration and subsequent long-term failure [4]. Potential culprits for longterm failure include immunological responses [5] and an increased calcium metabolism [6].…”

“…Patients need to wait significantly longer for surgery (up to 6 months or longer). In cases of rapidly deteriorating conditions surgeons are forced to use alternative xenograft valves such as glutaraldehyde-fixed procine valves as that used by Weimar et al [1]. The current results are alarming and indicate a strong need to refine and optimize biological valve substitutes for the growing young adolescent patient population.…”

“……allografts are the best valves for younger patients but surgeons are forced to use xenografts in cases of emergency… …Weimar and colleagues [1] are to be congratulated for highlighting the need to search for the optimal valve for young patients……”

“…In this issue of Biotechnology Journal, Weimer et al [1] report an important and interesting study comparing human heart valve transplants (allo-or homografts) with xenogeneic valves for reconstruction of the right ventricular outflow tract in patients undergoing aortic valve replacement.…”