Justin E. Davies  英国伦敦帝国学院

　　Justin E. Davies 英国国家心肺研究所心脏病学顾问。主要研究领域是先进技术的发展和应用，以了解疾病的发病机制，以及病理性疾病的诊断。

　　近年来，伦敦帝国学院Justin E Davies博士团队开发了一项新技术：瞬时无波型比值（instantaneous wave-free ratio， iFR）。心动周期中，血流阻力变化很大，iFR关注阻力小而稳定，且在血流较多的舒张期，对狭窄的辨别能力最强。检查在静息状态进行，只需5秒，无需注射血管扩张剂，使用与FFR类似的传统压力导管。

　　自2011年TCT会议上首次报告以来，iFR已用于评论1500多个冠状动脉狭窄病变。ADIVSE等研究使用同样方法计算iFR，都显示和FFR高度一致的分类。VERIFY研究使用自己的计算方法，结果与FFR差异较大，而使用帝国学院的评分技术分析这些数据则得出不同结果。这提示正确计算方法对于iFR计算非常重要。近日公布的CLARIFY研究证实，iFR和FFR与HSR相比，静息和充血时的指数无区别，且分类匹配率达92%。近期，伦敦帝国学院Hammersmith医院进行首次人体iFR测量，使用帝国学院开创的方法，在3个大洲进行超过150例检查。这项技术大大简化生理学评估，缩短检查时间，尤其有利于3支病变患者。

　　iFR: A New Technique for the Assessment of Coronary Artery Stenoses

　　The physiological interrogation of coronary artery stenoses with a pressure wire has been demonstrated to be important in guiding angioplasty. By choosing to only intervene on coronary stenoses which are physiologically significant， outcomes improveand only truly ischaemic lesions are treated. Recently these techniques have gained class Ⅰa status in the ESC guidelines， and have become an important part of the appropriate use criteria in the USA.

　　Recently， our group at Imperial College London have developed a new technique， instantaneous wave-free ratio (iFR). Rather than using the entire phase of the cardiac cycle where resistance is very varied and high， we isolate a window in diastole - the wave-free period - when resistance is naturally low， very stable， and flow significantly higher. This provides the greatest potential for stenosis discrimination， all carried out under resting conditions without administration of vasodilators such as adenosine.  Measurements take around 5 seconds， and use a conventional pressure wire similar to that used in FFR assessments.

　　The Superiority of iFR over Conventional FFR Technology and Its Development Prospects

　　Since iFR was first presented at TCT in 2011， assessment has been made in over 1500 stenoses. ADVISE was the first study to present， and since then the ADVISE-Registry， and the South Korean studies have reported. These all used the same algorithms to calculate iFR， and all show a consistently high classification match against FFR as a gold standard. Another smaller prospective analysis was performed by the VERIFY investigators using their own calculation technique. This demonstrated a significantly worse agreement between VFR (the VERIFY investigators version of iFR) with FFR. However， when this data was analysed using the original calculation techniques developed at Imperial College， by Gregg Stone and Allen Jeremias in the Cardiovascular Research Foundations Physiology Core laboratory， the findings were markedly different. Dr. Jeremias reported at TCT 2012， that the RESOLVE study had found an agreement between iFR and FFR similar to that found in the ADVISE studies. This suggested that correct calculation methodology is critical for calculation of iFR， a message which has been further supported by Habib Samady’s recent JACC editorial.

　　This week， the CLARIFY study has been reported in JACC. This study demonstrated that when iFR and FFR are compared against another true pressure-flow gold standard (HSR)， it is not possible to distinguish between resting and hyperaemic indicies which both have a classification match of 92%.

　　Recently， the first-in-man iFR measurement have been made at Hammersmith Hospital Imperial College London. This console commercialized by Volcano Corporation， uses the algorithms developed at Imperial College (Figure 1). Since the first measurements have been made in Jan 2013， over 150 iFR measurements have been made in across three continents. This technology rapidly simplifies physiological assessment， hugely cutting the time for making stenosis assessment， which is particularly advantageous in patients with 3 vessel disease. Dr. Eric Van Belle， Lille， France presented a case series comparing iFR to FFR at the French cardiac society. He reported a halving of measurement time when using iFR as opposed to FFR， which is particularly marked when assessing patients with 3 vessel disease.

　　Currently iFR is being formally assessed in a number of prospective clinical trials. The ADVISE 2 study， a large prospective multi-centre， international study with Javier Escaned as principal investigator， will further explore the iFR-FFR relationship. Other studies are looking at the improvement of iFR after PCI， and to further evaluate its ability to detect ischaemia against non-invasive tests. These studies continue to build an evidence base to support the use of iFR as a pressure-only adenosine-free assessment tool for evaluation of coronary artery stenoses.

　　图1.  使用iFR评估右冠状动脉开口狭窄