International Circulation:  First I would like to ask you Professor Bax.  What do you think is the optimal indications of IVUS and what about during PCI procedures， do you think IVUS should be a routine test?
《国际循环》：Bax教授，您认为血管内超声（IVUS）的最佳适应症是什么？在PCI中应用IVUS的情况如何，是否应当常规行IVUS检查？

Prof. Bax: It is a bit of a difficult question because I believe that if you have a clear history of a patient that comes to you with obvious chest pain， even better ischemia has been documented， and you do an invasive procedure， you see an obstructive stenosis – obstructive you can debate about what is obstructive， 50% -70% luminal narrowing.  More than 50% stenosis is what most people accept， and then I would have no doubt about doing the PCI and stent the lesion. 

The problem comes when you have an intermediate case.  You do an angiogram and you do see an intermediate lesion， you’d like to have more evidence to see what is going on.  You do an IVUS to see how extensive the atherosclerosis is in the vessel wall.  Frequently what we also do is a measurement of FFR where you measure the resistance over the lesion so you that can determine whether the intermediate lesion， whether it has hemodynamic consequences.  If there is a dramatic drop of pressure measured over the lesion with the FFR then an intervention would be useful.  If not， then an intervention is not useful as recently demonstrated by the FAME trial in the New England Journal of Medicine a couple of months ago.

I believe that there is also other fields where IVUS is of importance and that is for example now a days we use a lot of cardiac CT angiography.  So for patients with not a clear cut story but let’s say some risk factors the first step can be in some instances， a CT angiogram.  You get a non invasive angiogram but of the CT you also see not only the obstructive stenosis or the luminal narrowings but you also see lesions in the vessel wall.  Sometimes on CT it is hard to differentiate whether it is in the vessel wall or whether it is really obstructive.  In these patients we do an angiogram and if we don’t get such a good feeling about what is going on， then we like to do an IVUS to confirm whether the lesions are basically located in the intravessel wall or not.  So that is where we do the IVUS.  So PCI we discussed and I gave you something additional in patients with intermediate complaints.  CT done， you don’t know where you are， angiogram – a bit intermediate， and IVUS confirming. 

Bax教授：这个问题有点难度；如果患者有明确的明显胸痛病史，或者记录下心肌缺血的客观证据会更好，行有创检查后，若看到阻塞性狭窄——对阻塞可以有不同的定义，50%~70%管腔狭窄可以算作一个标准。狭窄超过50%大部分人可以接受；我对行PCI手术，在病变处植入支架无疑意。

但是若是一位中度病变患者，问题来了。行过冠状动脉造影检查，看到了一个中度病变，若想得到更多的证据，需行IVUS检查，看清在血管壁上粥样硬化程度。我们往往通过测定病变处阻力来计算FFR（心肌血流储备），以确定此中度病变对血流动力学有无影响。数月前发表在新英格兰医学杂志上的FAME实验研究表明，若病变处FFR测定压力急剧下降，行冠脉介入有益；若没有压力明显下降，则无益。

本人相信在其他领域IVUS亦有用武之地。现在心脏CT图象术亦得到颇多应用。对于那些病史不明晰，仅有危险因素患者，第一步首选冠状动脉CT检查。尽管冠脉CT为无创检查，但在CT图象上阻塞性狭窄或者管腔内狭窄或血管壁病变是混淆在一起的。有时CT无法区分病灶位于血管壁内还是腔内阻塞性病灶。在这些难以确诊的患者，我们行冠状动脉造影术，若仍无法确定病变性质，则行IVUS检查明确到底病灶位于血管壁内还是壁外。这是行IVUS检查的步骤。对于那些中度胸痛主诉的患者，行冠脉CT检查，不能确诊，冠脉造影，最后可以行IVUS确诊。

International Circulation:  What is the difference between the intracoronary OCT and IVUS? What are some of the advantages or the problem of the intracoronary OCT and comparing those two techniques?
《国际循环》：冠脉内OCT和IVUS相比，不同在哪里？比较这两种技术，冠脉内OCT技术的优点有哪些？

Prof. Bax: Well there are different types of patients you can deal with.  There are also a lot of different clinical questions.  The main way of thinking we have been doing is patient with chest pain， chronic chest pain， then intermittent chest pain.  Not an acute story.  These patients who come and then we need to make a decision about what are we going to do.  It can be a medical treatment or an interventional treatment. 

Based on lesions severity， ischemia， FFR – what we just discussed， we can do an intervention or not. This is the story about lesion severity ischemia.  On the other hand， you have the patients presenting with lets say a semi acute coronary syndrome suspected story.  If it’s not a clear cut acute coronary syndrome but something in between something we switch to invasive imaging in these patients then the question is more like ‘Is there a lesion that could be potentially harmful resulting in plaque rupture and acute event?”.  That is hard to detect and then we are usually not speaking about obstructivity but we are speaking about the vulnerable lesions.  The vulnerable lesions are something you can not detect with IVUS because with IVUS you can only see whether there is atherosclerosis in the vessel wall.  It is very good for that， probably the best， state of the art technique to detect any atherosclerosis in the coronary vessel but it does not tell me whether the lesion is at risk.  That is what we ideally like to know. 

That is why certain non invasive techniques particularly in the field of nuclear molecular imaging try to learn about abnormalities in the vessel wall whether they are prone to rupture， whether they show signs of inflammation， or signs of reactivity.  These are signs of vulnerability.  Now we are not getting that far at the moment.  First of all we do not really know what characterizes a vulnerable lesion， we have some ideas.  There is a story about the thin cap fibroatheroma but to image that what we are really looking for is difficult.  At the moment non invasive imaging has been reported with 18-F Fluoro Deoxyglucose.  When they measured the glucose utilization of the vessel wall and they have seen in active lesions， the FDG update is increased.  So these are sort of molecular markers of imaging. 

Now going back to OCT， OCT is the highest resolution technique that we have.  If you do an OCT in a patient presenting with an acute coronary syndrome you can really see the rupture of the plaque， you can see small thrombus formations， so this is the best technique to look at the lesions whether something is going on or not.  The disadvantages of this approach are that it is invasive but even more you have to do it during emptiness of the blood in the vessel.  That seems to be painful for the patient.  So these are difficult procedures but eventually this sort of procedures， non invasive molecular imaging or invasive OCT， are more in the direction of detecting a vulnerable lesion that is going to rupture.

Bax教授：不同患者，不同的处理方式；临床问题也是不同的。我们目前考虑治疗的是有胸痛、慢性胸痛和间断胸痛患者，而非急性患者。他们来就诊，我们给出治疗决策：药物治疗或者手术介入治疗。

基于病灶严重程度、缺血情况和FFR，临床医生做出介入手术与否的决定。另外，若患者是疑似亚急性冠状动脉综合症患者，介入术中我们需要考虑的问题是：“此病变有多大的危害，是否会变为破裂斑块，导致急性心血管事件？”很难回答的问题；这时候阻塞本身不是大问题，而是不稳定病变是我们