Transcatheter implantation of a prosthesis in a degenerated aortic bioprosthesis [valve-in-valve (ViV)] was initially an off-label application of transcatheter aortic valve implantation (TAVI), which rapidly appeared of interest since patients with degenerated bioprostheses are likely to be at higher risk for surgery than those with native aortic stenosis. Transcatheter ViV is now recognized as an option for patients at high risk for surgery in American and European guidelines. Transcatheter aortic ViV accounted for 3.3% of all TAVI procedures between 2012 and 2015 in the Society of Thoracic Surgeons/ American College of Cardiology (ACC) Transcatheter Valve Therapy Registry, and the rate of ViV increased from 1.7% between 2010 and 2012 to 4.4% between 2013 and 2015 in the FRANCE-2 and FRANCE TAVI registries. The number of ViV procedures is likely to increase in the future given the growing use of bioprostheses over the last decades, in particular in younger patients. 5,6 The study by Ribeiro et al. published in this issue of the journal draws attention to coronary obstruction in the particular case of transcatheter aortic ViV procedures. The rationale for studying this rare but severe complication in patients undergoing ViV was justified by a previous study showing higher rates of coronary obstruction after transcatheter ViV than after TAVI for native aortic stenosis. A strength of this study is that it is based on the largest experience in ViV from a multicentre international registry totalling 1612 procedures. The 2.5% rate of coronary obstruction after ViV found in the previous study was based on only three cases of coronary obstruction out of 121 patients. The 2.3% rate reported in the present study is consistent but more robust since it is calculated from 37 cases of coronary obstruction occurring in 1612 patients who underwent ViV procedures. The true rate of coronary obstruction is probably higher due to the possibility of clinically silent cases, in particular in patients with previous coronary artery bypass grafting. In addition to more accurate estimations, the study of a larger number of cases allows for the search of predictive factors. The only clinical factor significantly associated with the risk of coronary obstruction was the presence of a stentless prosthesis or a stented prosthesis with externally mounted leaflets. These findings are consistent with smaller series and can be interpreted by a higher risk of interaction between the bioprosthetic cusps and coronary ostia, most often involving the left coronary artery. Conversely, the 0.7% rate of coronary obstruction reported after ViV in patients who have a stented prosthesis with externally mounted leaflets is not higher than after TAVI in patients with native aortic stenosis. This is of importance since stented prostheses with internally mounted leaflets have been widely used. With regards to the prosthesis implanted during transcatheter ViV, there was no significant difference in coronary obstruction rate between balloon-expandable and selfexpanding prostheses (Figure 1). However, coronary obstruction may occur later with self-expanding than balloon-expandable prostheses. This finding raises questions regarding the mechanism of delayed obstruction and optimal patient monitoring. Another predictive factor of coronary obstruction is related to imaging. The authors describe a new measurement obtained from computed tomography (CT) scan, the virtual transcatheter valve to coronary ostium (VTC) distance, which appears to be strongly associated with the risk of coronary obstruction. The value of VTC distance to predict coronary obstruction should, however, be interpreted with caution. First, analysis of CT scans was performed in a subset of 20 of the 37 patients of the whole population. Secondly, the suggested cut-off value of VTC distance to predict coronary obstruction raises the question of its reproducibility when analysed outside a central core lab. Thirdly, multivariable analysis of CT data in this paper is a case–control study with potential inherent bias.

中文翻译：

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冠状动脉阻塞：经导管主动脉瓣中瓣植入术中罕见但具有破坏性的并发症

在退化的主动脉生物瓣 [瓣中瓣 (ViV)] 中经导管植入人工瓣膜最初是经导管主动脉瓣植入术 (TAVI) 的标签外应用，由于退化生物瓣膜的患者很可能手术风险高于自体主动脉瓣狭窄患者。Transcatheter ViV 现在被美国和欧洲指南公认为手术风险高的患者的一种选择。在胸外科学会/美国心脏病学会 (ACC) 经导管瓣膜治疗登记处，经导管主动脉 ViV 占 2012 年至 2015 年所有 TAVI 手术的 3.3%，ViV 的比率从 2010 年至 2012 年的 1.7% 增加到 4.4% 2013 年至 2015 年在 FRANCE-2 和 FRANCE TAVI 登记处。鉴于过去几十年中生物假体的使用越来越多，特别是在年轻患者中，ViV 手术的数量在未来可能会增加。5,6 Ribeiro 等人的研究。发表在本期杂志上的文章提请注意经导管主动脉 ViV 手术特殊情况下的冠状动脉阻塞。在接受 ViV 的患者中研究这种罕见但严重的并发症的理由是，先前的一项研究表明，经导管 ViV 后冠状动脉阻塞的发生率高于 TAVI 治疗天然主动脉狭窄后的冠状动脉阻塞率。这项研究的一个优势在于，它基于来自一个多中心国际注册处的 ViV 的最大经验，总计 1612 个程序。2. 在先前的研究中发现 ViV 后 5% 的冠状动脉阻塞率是基于 121 名患者中只有 3 例冠状动脉阻塞。本研究报告的 2.3% 的比率是一致的，但更可靠，因为它是根据 1612 名接受 ViV 手术的患者中发生的 37 例冠状动脉阻塞计算得出的。由于临床无症状病例的可能性，冠状动脉阻塞的真实发生率可能更高，特别是在既往冠状动脉旁路移植术的患者中。除了更准确的估计之外，对大量案例的研究还允许搜索预测因素。与冠状动脉阻塞风险显着相关的唯一临床因素是无支架假体或带有外部安装小叶的支架假体的存在。这些发现与较小的系列结果一致，并且可以通过生物假体瓣尖和冠状动脉口之间相互作用的更高风险来解释，最常涉及左冠状动脉。相反，在具有外置瓣叶的支架式假体患者中，ViV 后报告的冠状动脉阻塞率为 0.7%，但不高于具有天然主动脉瓣狭窄患者的 TAVI 后。这一点很重要，因为带有内部安装小叶的支架假体已被广泛使用。关于在经导管 ViV 期间植入的假体，球囊扩张式和自扩张式假体之间的冠状动脉阻塞率没有显着差异（图 1）。然而，与球囊扩张式假体相比，自扩张式假体的冠状动脉阻塞可能发生得更晚。这一发现提出了关于延迟阻塞机制和最佳患者监测的问题。冠状动脉阻塞的另一个预测因素与成像有关。作者描述了从计算机断层扫描 (CT) 扫描中获得的新测量值，即虚拟经导管瓣膜到冠状动脉口 (VTC) 的距离，这似乎与冠状动脉阻塞的风险密切相关。然而，应谨慎解释 VTC 距离预测冠状动脉阻塞的价值。首先，对整个人群的 37 名患者中的 20 名患者进行 CT 扫描分析。其次，当在中央核心实验室外进行分析时，建议的 VTC 距离预测冠状动脉阻塞的临界值引发了其可重复性的问题。第三，