Justin E. Davies 英国伦敦Imperial College
无创检查评估血流储备分数FFR
HeartFlow技术采用计算机流体动力学模型，通过CT图像来评价FFR，实质是应用Navier Stokes方程计算动脉全长中每一个部位的压力衰减特征，据此得出FFR。无创技术的目的是更好对冠心病高危患者进行危险分层。
There are currently several groups developing several techniques， the most prominent is the HeartFlow company， which is using a computational fluid dynamics model to assess a fractional flow measurement via CT imaging. HeartFlow essentially uses the Navier-Stokes equations to solve pressure drop characteristics at each individual location along the length of the artery. From that， they are able to derive the fractional flow measurement. Only in one study has this technique been compared against invasive FFR. The goal of these techniques is to better risk stratify people with a higher probability of having coronary disease than could be done otherwise from CT images alone， without the computed pressure measurements.
FFR灰色地带
所有研究都采用非常硬性的划界值，即依据较早的DEFER和FAME试验采取了0.75或0.8的划界值。在临床实践中，有些患者的FFR值处于划界值的附近，难以作出临床决策。FFR具有内在变异性，我支持给临床医生一个更为宽松的FFR值范围，而不是仅仅单纯地使用一个划界值。
We have recently published an article on this looking at both grey zone FFR - between 0.75 and 0.8 - and the reproducibility of FFR measurements. All of the studies have been done using a fixed cut point， either 0.75 or 0.80， relying on data from the DEFER and FAME studies. This allows characterization of people into one group or the other. In clinical practice， that can often cause some problems because you have people who are borderline， which makes decisions difficult. From a scientific perspective， the best way to do this is to make a measurement， wait ten minutes， repeat， and take an average of the two. However， time is limited in the cath lab and this kind of measurement is not realistic. As a result of the intrinsic variability of these indices I would， like my colleagues， advocate more leniency than a pure 0.80 cut off. For instance， the measurements we have actually performed have all been based around a 0.80 cut off， and they show that， within a window of 0.77 to 0.83， there is a probability to straddle the 0.80 cut off. You could get a different answer if you made the measurement a second time. Within that zone， physicians should be given more room to either treat or not treat. For instance， if you had a value of 0.79 and a vessel that looked almost unobstructed， then you may want to leave it alone. If the value was 0.81， you may want to stent that vessel. I think this is an entirely reasonable and pragmatic approach to what otherwise would be answered by repeated measurements of this technique， which is not practical in a cath lab.
FFR评价非ST段抬高急性冠状动脉综合征
对非罪犯血管的评价，FFR非常有用。对罪犯血管，如有任何疑问，光学相干成像等技术可以补充FFR，共同给出血管病变的清晰描述。
In the non-culprit vessel， I think it is a very good use of the technique. I think in a culprit vessel， where the non-STEMI has occurred， and if there is clearly a ruptured plaque， you are no longer treating for symptoms reduction and are instead treating for the preservation of blood flow. In this case， stenting is used to squash the plaque against the wall and prevent a cascade of events which may lead to a thrombus and the development of an ST- elevated myocardial infarction. In this setting FFR can be complimented if there are any risks or further questions with other techniques such as OCT， which can give a very clear delineation of the vessel. If there is ever any doubt of a ruptured plaque， this can show it clearly.
FFR作为判断病变是否需治疗的主要标准
当我们观察自认为是正常或接近正常的动脉时，FFR测定可能为异常；当推断患者有显著病变或临界病变， FFR测定可能完全正常。因此， FFR测定可能彻底改变临床决策。
There is a body of evidence that supports the use of fractional flow reserve. FFR works very well when， in a normal-looking artery with an intermediate lesion， you put the wire down and discover a low FFR value. In this case， a normal-looking patient who would have been left alone would receive treatment， confirming any symptoms they may have had. The corollary is then the FFR appears normal in someone you think has a significant or borderline lesion. These two different circumstances demonstrate the real value of FFR. Clearly， if an artery looks unobstructed， a wire will confirm or refute any suspicions. However， the real power of FFR is identifying patients in whom you think are likely to be negative or positive and it flips the coins around: it essentially reverses your decision. The beauty of the technique， as any physiology based technique， is that it models not just the discrete individual stenosis but also the whole effect of these little stenoses along the length of the vessel and what effect it ultimately has on a pressure drop. FFR is a nice way of compiling everything into a single measure.