Dagum P, Green G R, Timek T A, Daughters G T, Foppiano L E, Tye T L, Bolger A F, Ingels N B, Miller D C
Department of Cardiovascular and Thoracic Surgery, Stanford University School of Medicine, Stanford, CA 94305-5247, USA.
Circulation. 1999 Nov 9;100(19 Suppl):II70-7. doi: 10.1161/01.cir.100.suppl_2.ii-70.
Recently, renewed interest in allograft and stentless "freehand" bileaflet xenograft mitral valve replacement has arisen. The variability of human papillary tip anatomy and scarcity of donors limit allograft availability, making xenograft mitral valves an attractive alternative; however, these valves require new surgical implantation techniques, and assessment of their hemodynamics and functional geometry is lacking.
Seven sheep underwent implantation of a new stentless, glutaraldehyde-preserved porcine mitral valve (Physiological Mitral Valve [PMV], Medtronic) and were studied acutely under open-chest conditions. A new method of retrograde cardioplegia was developed. Hemodynamic valve function was assessed by epicardial Doppler echocardiography. 3D motion of miniature radiopaque markers sutured to the valve leaflets, annulus, and papillary tips was measured. Six other sheep with implanted markers served as controls.
Both papillary muscle tips avulsed in the first animal, leaving 6 other animals. Mitral regurgitation was not observed in any xenograft valve. The peak and mean transvalvular gradients were 4.6+/-1.8 mm Hg and 2.6+/-1.5 mm Hg, respectively. The average mitral valve area was 5.7+/-1.6 cm(2). Valve closure in the xenograft group occurred later (30+/-11 ms, P<0. 015) and at higher left-ventricular pressure (61+/-9 mm Hg, P<0.001) than in the control group; furthermore, leaflet coaptation was displaced more apically (5.6+/-2.2 mm, P<0.001) and septally (5. 8+/-1.5 mm, P<0.001), and the anterolateral papillary tip underwent greater septal-lateral displacement (2.7+/-1.5 mm, P<0.001). Annular contraction during the cardiac cycle was similar in the 2 groups (xenograft 9.2+/-4.5% versus control 10.6+/-4.5% [mean+/-SD; 2-factor ANOVA model]).
Successful freehand stentless porcine mitral valve implantation is feasible in sheep and was associated with excellent early postoperative hemodynamics. Physiological mitral valve annular contraction and functional leaflet closure mechanics were preserved. Long-term valve durability, calcification, and hemodynamic performance remain to be determined in models.
最近，人们对同种异体移植和无支架“徒手”双叶异种移植二尖瓣置换术重新产生了兴趣。人类乳头肌尖端解剖结构的变异性和供体的稀缺限制了同种异体移植的可用性，这使得异种移植二尖瓣成为一种有吸引力的替代方案；然而，这些瓣膜需要新的手术植入技术，并且缺乏对其血流动力学和功能几何学的评估。
对7只绵羊植入一种新的无支架、戊二醛保存的猪二尖瓣（生理性二尖瓣[PMV]，美敦力公司），并在开胸条件下进行急性研究。开发了一种新的逆行心脏停搏方法。通过心外膜多普勒超声心动图评估瓣膜的血流动力学功能。测量了缝合到瓣膜小叶、瓣环和乳头肌尖端的微型不透射线标记物的三维运动。另外6只植入标记物的绵羊作为对照。
第一只动物的两个乳头肌尖端均撕脱，其余6只动物存活。在任何异种移植瓣膜中均未观察到二尖瓣反流。跨瓣峰值和平均梯度分别为4.6±1.8mmHg和2.6±1.5mmHg。平均二尖瓣面积为5.7±1.6cm²。异种移植组瓣膜关闭发生时间较晚（30±11ms，P<0.015），且发生时左心室压力较高（61±9mmHg，P<0.001）；此外，小叶对合点更偏向心尖（5.6±2.2mm，P<0.001）和间隔（5.8±1.5mm，P<0.001），前外侧乳头肌尖端的间隔-外侧移位更大（2.7±1.5mm，P<0.001）。两组在心动周期中的瓣环收缩情况相似（异种移植组9.2±4.5%，对照组10.6±4.5%[均值±标准差；双因素方差分析模型]）。
在绵羊中成功进行徒手无支架猪二尖瓣植入是可行的，且术后早期血流动力学良好。生理性二尖瓣瓣环收缩和小叶功能关闭机制得以保留。瓣膜的长期耐用性、钙化情况和血流动力学性能仍有待在模型中确定。
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