Delivering the best result in complex coronary intervention requires the routine use of coronary imaging. This is an article giving an in-depth discussion about IVUS OCT. For simplicity, I will write this blog in a format of questions as commonly asked by our patients.
IVUS and OCT FAQs
You: What are IVUS and OCT?
Dr BR: IVUS and OCT are two different techniques. Both are types of coronary imaging. Coronary imaging means seeing coronary arteries from inside, as we see our intestines in endoscopy.
IVUS stands for IntraVascular Ultrasound, and OCT stands for Optical Coherence Tomography
You: Is it same as angiography?
Dr BR: Not at all, It is beyond angiography. Angiography shows the lumen shadow. It uses dye to fill the artery lumen, which is then seen through Xray. Angiography does not show the wall. IVUS and OCT both show the lumen as well as the wall of the coronary artery.
You: Why we need to see Wall of the artery? Do the blockages are in lumen or wall?
Dr BR: The blockages are actually within the wall and causing narrowing of the lumen. Now to answer your first question, I will take the help of this scenario.
Patient A is having the same angiography picture as Patient B, but Patient B is having significant coronary blockages within the wall of the artery. This can be reported as even normal angiography by an inexperienced angiographer. With experience, we will be able to differentiate these two images as different and find out which patient needs coronary imaging to see the cholesterol deposition within the wall.
You: So does all angiography even if normal needs coronary imaging?
Dr BR: No, as I mentioned, with help of clinical background, report of a stress test and with an experienced eye, we will be able to differentiate this two same looking angio as a different one. Coronary Imaging will help to establish the disease and treatment
You: Oh, is it the reason that some of the normal angiography patients also turns out to have a heart attack later on,?
Dr BR: It is indeed a possibility.
You: In case blockages are already seen by angiography, do we need IVUS or OCT?
Dr BR: Yes, IVUS and OCT give the exact percentage of blockages, length of blockage, the type of blockage, whether its due to cheesy fat, tight fibrous tissue or hard calcium tissue. This information is vital in deciding the modality of therapy( angioplasty vs bypass). This information helps a lot in choosing the stent size and diameter. Optimum dilatation of stent as confirmed by OCT or IVUS makes chances of developing restenosis negligible.
You: So is it that if IVUS/OCT done during angioplasty will end up in better result angioplasty?
Dr BR: Definitely. Numerous scientific papers are documenting this fact. IVUS guided angioplasty results in better stent sizing, better stent opposition to a wall and decreased chances of stent failure. This all gives overall very good long term results.
You: How you do this IVUS/OCT?
Dr BR: The same way we pass any wire or catheter inside the heart’s artery, we pass IVUS/OCT catheters. These are special catheters which have an imaging probe (Camera) over the tip. These catheters are then connected to computers outside which displays the archived images.
You: Is it risky? Using IVUS or OCT increases any procedure complications?
Dr BR: Overall both are safe procedures. Chances of vessel tear due to IVUS or OCT catheter are very rare but yes they can happen rarely.
You: Does all angioplasty do require IVUS /OCT?
Dr BR: There are some countries, like Japan, where almost all angioplasties are done with the help of this technology. In the US, almost one-third of the procedures are done with coronary imaging and almost all complex coronary interventions are done with coronary imaging. Here in India, the use of coronary imaging is limited. This is mainly due to cost constrain and lack of experience in this technology. At Zydus, over the last few years, we have performed more than 150 complex coronary interventions under IVUS guidance with a very good result and zero rates of procedure-related complications.
You: What are the cases in which you would recommend to have IVUS guided or OCT guided angioplasty?
Dr BR: Science says that using IVUS during angioplasty can help in 50 to 70% of the cases. Nowadays, the majority of cases are diabetic patients having long segment blockage with some renal impairment. They have a blockage at the bifurcation of the main branch. They do have previous stents and now that has failed. These are all must cases in which IVUS is recommended.
Talking about the CTO lesions, which we call as Chronic Total Occlusions, these are one of the most complex types of coronary angioplasties and use of IVUS in this improves the procedure success chances to a great extent.
Another subset of patients benefitted from the IVUS guided angioplasty is the renal failure patients. With increasing experience of the IVUS images, we can create the mental image of the entire artery and its disease extent with the location of the block and its relation to its side branches. Then, Angioplasty is performed without giving contrast at all. This is called Zero-contrast angioplasty. Yes, we do not use a single drop of contrast at all. Removing the renal risk due to contrast at all from the procedure. So renal failure patient with bordering renal function and not requiring dialysis are benefitted most. Otherwise, this essential procedure, if done with contrast, increases renal load further and the patient may require dialysis. IVUS prevents this as it does not require Contrast injection.
OCT can not be used for zero contrast angioplasty as acquiring OCT images itself requires injection of contrast material. There are some newer developments in OCT technology which uses other renal safe contrasts but still, the quality of images are suboptimal.
You: Do you use both IVUS and OCT in the same patient?
Dr BR: No, we use either of them. As IVUS does not require contrast injection, it has preference over OCT in our settings. OCT advantage is its excellent picture quality and less experience needed to interpret the images with a rapid learning curve. IVUS imaging learning requires good experience on the part of the operator. In special cases where we need very good quality pictures of the previously implanted stent, then we go for the OCT. Otherwise, IVUS serves almost all the needs of complex angioplasty.
You: Can you decide the need for the stent based on this coronary imaging as it measures the block accurately?
Dr BR: When we are in the dilemma of whether the patient requires removal of a block or not, it is not the percentage blockage which decides the need to open the artery. Yes, you heard it right. Need to open a blocked artery by say 70-80%, is not decided by the percentage of blockages but by the documented ischemia due to that block. So, for deciding the indication of stenting we take help of other modality. We use FFR. FFR is a fractional flow reserve. IVUS and OCT are not and should not be used to decide indication for the angioplasty procedure in general.