Koolbergen Dave R, Hazekamp Mark G, de Heer Emile, van Hoorn Frans, Huysmans Hans A, Bruijn Jan A, Dion Robert A E
Department of Cardiothoracic Surgery, Leiden University Medical Center, Leiden, The Netherlands.
Eur J Cardiothorac Surg. 2002 Nov;22(5):802-7. doi: 10.1016/s1010-7940(02)00435-9.
The limited availability of donor valves and experimental evidence that pulmonary valves can withstand systemic pressure made us use cryopreserved pulmonary homografts as aortic valve substitutes. We observed a high incidence of early reoperation because of severe graft insufficiency due to cuspal tears. The mid-term results are evaluated in this study and histological analysis of explanted homografts is performed to investigate the cause of graft failure.
From December 1991 to April 1994, 16 patients (13 male; mean age 37.3 years, range 21-59 years) underwent aortic valve replacement with a cryopreserved pulmonary homograft. The indication was endocarditis (n = 4), bioprosthesis degeneration (n = 3) or congenital aortic valve disease (n = 9). All homografts were implanted freehand in the subcoronary position. All patients were contacted for follow-up and recent echo-Doppler studies were reviewed. Six explanted homografts were examined microscopically using routine histological techniques to analyze changes in cell population, collagen and elastic fiber structure.
Follow-up was complete in all patients. Reoperation was required in ten patients because of severe graft incompetence (mean implantation time 5.9 years, range 2.8-8.0 years). In two patients, recurrent endocarditis was the cause of graft failure. In the other eight patients the leaflets looked pliable and thin with gross tearing in one or more cusps. The histopathologic changes observed were remarkably similar in all examined grafts: the cusp tissue was almost non-cellular and the collagen fiber structure had mostly disappeared. At the site of rupture, the tissue had become thin with strongly degenerated collagen and elastic fiber structure. In the six patients with a homograft remaining in situ, echo-Doppler showed trivial to mild insufficiency in five cases and moderate to severe in one case, whereas no significant gradients were observed.
We concluded that structural reduction of cell number and degenerative alterations in the molecular composition of the extracellular matrix in valve tissue is the main cause of early graft failure in this series. The use of cryopreserved pulmonary homografts in the systemic circulation is therefore not advised.
由于供体瓣膜供应有限，且有实验证据表明肺动脉瓣能够承受体循环压力，我们使用冷冻保存的肺动脉同种异体移植物作为主动脉瓣替代物。我们观察到，由于瓣叶撕裂导致严重的移植物功能不全，早期再次手术的发生率很高。本研究评估了中期结果，并对取出的同种异体移植物进行组织学分析，以探究移植物失败的原因。
1991年12月至1994年4月，16例患者（13例男性；平均年龄37.3岁，范围21 - 59岁）接受了冷冻保存的肺动脉同种异体移植物主动脉瓣置换术。适应症为心内膜炎（n = 4）、生物假体退变（n = 3）或先天性主动脉瓣疾病（n = 9）。所有同种异体移植物均徒手植入冠状动脉下位置。对所有患者进行随访，并回顾近期的超声多普勒研究。使用常规组织学技术对6个取出的同种异体移植物进行显微镜检查，以分析细胞数量、胶原蛋白和弹性纤维结构的变化。
所有患者均完成随访。10例患者因严重的移植物功能不全需要再次手术（平均植入时间5.9年，范围2.8 - 8.0年）。2例患者中，复发性心内膜炎是移植物失败的原因。在其他8例患者中，瓣叶看起来柔软且薄，一个或多个瓣尖有明显撕裂。在所有检查的移植物中观察到的组织病理学变化非常相似：瓣尖组织几乎无细胞，胶原蛋白纤维结构大多消失。在破裂部位，组织变薄，胶原蛋白和弹性纤维结构严重退变。在6例同种异体移植物仍在位的患者中，超声多普勒显示5例有轻微至轻度功能不全，1例有中度至重度功能不全，未观察到明显压差。
我们得出结论，瓣膜组织中细胞数量的结构性减少和细胞外基质分子组成的退行性改变是本系列中早期移植物失败的主要原因。因此，不建议在体循环中使用冷冻保存的肺动脉同种异体移植物。
