David T E
Division of Cardiovascular Surgery of The Toronto Hospital and University of Toronto, Ontario, Canada.
J Card Surg. 1998 Sep-Oct;13(5):344-51. doi: 10.1111/j.1540-8191.1998.tb01096.x.
The implantation of stentless porcine valves (SPVs) is technically more demanding than implantation of stented bioprosthetic valves. Implantation of the Toronto SPV bioprosthesis requires an,understanding of the relationships between the leaflets and the aortic annulus and sinotubular junction. In addition to proper alignment of the three commissures within the aortic root, the diameter of sinotubular junction should not exceed the external diameter of the porcine aortic valve after completion of the operation. The Medtronic Freestyle porcine aortic root bioprosthesis can be used for subcoronary implantation as well as for aortic root replacement. Degenerative calcification of a tricuspid aortic valve is the most common cause of aortic valve disease in older patients. Implantation of stentless valves in the subcoronary position is usually feasible because the geometry of the aortic root is well maintained in these patients. The bicuspid aortic valve is the second most common cause of aortic valve disease in older patients and the most common in younger patients. These patients frequently have dilated aortic root, and the Medtronic Freestyle bioprosthesis is ideal for implantation using the root inclusion technique. Stentless porcine bioprostheses are minimally obstructive and associated with low mean systolic gradients. In addition, they have better hemodynamic performance during exercise than stented bioprostheses. For these reasons, patient-prosthesis mismatch has not been described with stentless valves. Left ventricular function after aortic valve replacement appears to be better with stentless than with stented bioprostheses. Comparative, nonrandomized studies of aortic valve replacement with stented and stentless valves suggest that the risk of cardiac death is reduced with stentless valves and the rates of valve-related complications also appear to be lower. What remains unknown is whether stentless valves are more durable than stented ones.
无支架猪瓣膜（SPV）的植入在技术上比有支架生物瓣膜的植入要求更高。植入多伦多SPV生物瓣膜需要了解瓣叶与主动脉瓣环及窦管交界之间的关系。除了主动脉根部内三个瓣叶交界的正确对齐外，术后窦管交界的直径不应超过猪主动脉瓣的外径。美敦力Freestyle猪主动脉根部生物瓣膜可用于冠状动脉下植入以及主动脉根部置换。三尖瓣主动脉瓣的退行性钙化是老年患者主动脉瓣疾病最常见的原因。在冠状动脉下位置植入无支架瓣膜通常是可行的，因为这些患者的主动脉根部几何结构保持良好。二叶式主动脉瓣是老年患者主动脉瓣疾病的第二大常见原因，在年轻患者中最为常见。这些患者经常有主动脉根部扩张，美敦力Freestyle生物瓣膜是采用根部包裹技术植入的理想选择。无支架猪生物瓣膜阻塞最小，平均收缩期压差较低。此外，与有支架生物瓣膜相比，它们在运动时具有更好的血流动力学性能。由于这些原因，尚未有关于无支架瓣膜患者-假体不匹配的描述。主动脉瓣置换术后左心室功能似乎无支架瓣膜比有支架生物瓣膜更好。对有支架和无支架瓣膜进行主动脉瓣置换的比较性、非随机研究表明，无支架瓣膜可降低心脏死亡风险，与瓣膜相关的并发症发生率似乎也较低。尚不清楚的是无支架瓣膜是否比有支架瓣膜更耐用。
