Why should we rely on a blood test to assess heart disease risk when we can see the disease itself?
Transcript:
Introduction to Carotid Intima-Media Thickness test (CIMT).
Have you heard of a CIMT test or a Carotid Intima-Media Thickness test? Well, it turns out a CIMT is one of the best ways to screen for vascular disease that has no radiation, and that if you want you could repeat every few months. Not many tests fit those criteria, and a CIMT turns out to be one of the most beneficial. So what is a CIMT? What are some of the benefits? What are some of the drawbacks? How may it help you? Well, let’s get into the details. But before we get started, please remember our channels for informational purposes only. We’re not providing individual or group medical or healthcare advice for establishing a provider-patient relationship. Many of the interventions we discuss can be potentially dangerous if done without proper supervision, so consult your healthcare provider before changing your lifestyle or medications. I did a video recently discussing how cardiac imaging with either a calcium score or a CT angiogram are far superior to using LDL cholesterol for determining heart health or heart disease risk. After all, why rely on a surrogate blood test that is weakly predictive of vascular disease when you can test for the actual presence or absence of vascular disease, right? Pretty simple. Well, a number of you commented about, you know, “What about CIMT?” And it’s a great question. And one of the many reasons why we love it when you comment on our video so we can, you know, kind of learn what you’re thinking. And because of that, I want to get into the details of CIMT.
The bottom line is that a CIMT or Carotid Intima-Media Thickness (CIMT) Test is a potentially very helpful test. It screens for vascular disease in the carotid artery and it doesn’t have any radiation, so you can safely follow it every few months if you want. But it’s not covered by insurance and can be challenging to do correctly, which may limit its availability. But let’s start at the beginning, right? CIMT is an ultrasound test. It uses ultrasound waves and not x-rays and examines the carotid artery, the main artery in your neck, and it measures the intima media thickness, Intima-Media Thickness, meaning the thickness in millimeters or even fractions of millimeters of the layers of the endothelial or the lining of the vessel. Then there’s called “The Intima and the Media.” And a very important point is that this isn’t the standard carotid ultrasound done at most radiology centers or the lifeline screening companies. Those ultrasounds to the Carotid, look for the presence or absence of plaque, but they don’t measure the endothelial thickness. Whereas a CIMT does both, right? It measures the Endothelial thickness, and it looks for a plaque. But another downside is unfortunately almost no insurance providers here in the US will cover the CIMT. They can run anywhere from $75 up to $400 depending on where it’s done. So that’s definitely something to consider when looking for one of these tests. Now, some may say right off the bat, wait a second, I thought we were talking about heart health. So why are we talking about a neck artery? Well, that’s a good point. And plaque in the neck arteries can lead to a stroke, which is obviously pretty important in itself. So it’s a good idea not to ignore the neck arteries, but also there’s the concept that vascular disease is a systemic issue, not a local one. So if someone has progressive vascular disease in one artery, they likely have it in others. So in this case, the neck artery is used as a surrogate for the heart artery or the coronary artery, but it makes sense why, right? The coronary arteries, they’re hidden behind our sternum and our ribs and they’re between two and four millimeters in diameter, whereas the carotid artery is six to eight millimeters in diameter and is easily accessible in the neck right below the skin. So it’s much easier to image with ultrasound. And beside it being easier to access, studies have demonstrated an association between an abnormal CIMT, especially progression over time, and the risk of heart disease.
What do studies say about CIMT tests?
But one cool thing about CIMT is it also works in the opposite direction, meaning as it increases, cardiac risk goes up, but as it decreases, the cardiac risk goes down. And that’s important because if you’re using it to monitor effectiveness of a certain treatment, then you want to make sure it’s predictive in both directions. And a CIMT can add predictive value to other tests like a calcium score. One known drawback to a calcium score is it tends to be less predictive at a young age, especially like less than 40. Well, one study suggested the CIMT is much better in this younger population and has the added bonus obviously of no radiation exposure. Another study suggested calcium scores may be a better predictor in intermediate risk individuals, but CIMT might be better for lower risk individuals. So it’s important to know who we’re talking about when discussing the predictive benefit to a CIMT test. And let’s not forget the value of visualizing plaque and the type of plaque. So most CIMT studies don’t just measure the endothelial thickness. They also screen for plaque and they can show if the plaque is what we call “Echolucent or Echodense.” Echolucent plaque having sort of a higher risk of stroke or cardiac event, compared to echodense plaque, which tends to be a little bit more stable. So knowing the type of plaque can be really helpful. But remember, once plaque is present, that’s a later finding. It’s already had time to grow and progress. So it’s a finding of significant Atherosclerosis already being present. So similar to the presence of coronary calcium score on a CAC. So it’s another benefit of a CIMT. It can show both early and late vascular findings, with changes in the thickness of the artery as early and evidence of plaque as sort of later development.
Drawbacks of CIMT compared to other tests.
But CIMTs aren’t perfect, and one big drawback is that there’s nothing sort of automated about it. It’s very dependent on the operator and it can be technically challenging. They have to get the same site, the same angle, the same measuring technique with the ultrasound probe each and every time. So especially with some inexperienced operators, it can make a difference. So where you get it done, may be the most crucial element in deciphering how helpful the results actually are. And that’s why I recommend for people who follow the CIMT over time. If you can, it’s great to get it at the same institution with the same sonographer, so that there is that reproducibility over time.
Conclusion on CIMT and its uses.
So in conclusion, first, thank you for your questions to ask about the CIMT. But a CIMT is a reasonably good predictor of vascular disease, especially in the low risk and younger populations, although it can apply to others as well. It’s helpful for identifying plaque morphology, although this is a late finding, and it’s helpful to follow over time as it may show relatively good either rapid progression or regression. And there’s no radiation, so it can be followed frequently. But beware of the downsides, it’s not covered by insurance. There may be significant variability in the quality and technique between sonographers. And you have to make sure that the results are normalized for your age. For instance, a 0.7 millimeter IMT in a 40 year old, is not a great finding. But for a 70 year old, that’s kind of reassuring, right? So where do you stand on that spectrum? So where does a CIMT fit with a calcium score and a CT angiogram? Well, in a high risk population, a single CIMT measurement may not be as predictive for coronary events, depending on the technique and findings and so forth. But it may be more predictive in younger and lower risk populations, and it’s easier to follow for progression or regression, and it provides additive predictive value over time.
So I hope this was helpful to sort of better understand where a CIMT falls in the workup for vascular disease. And I hope it provides you with knowledge to discuss it with your healthcare provider. So let us know what you think and what your experiences with CIMTs as we love to get your comments. And that’s why I’m even doing this video because of your comments. So thank you so much for watching. I’m Dr. Bret Scher, and we’ll see you here next time at Metabolic Mind, a nonprofit initiative of Baszucki Group. I want to take a brief moment to let our practitioners know about a couple of fantastic free CME courses developed in partnership with Bazucki Group by Dr. Georgia Ede and Dr. Chris Palmer. Both of these free CME sessions provide excellent insight on incorporating metabolic therapies for mental illness into your practice. They are approved for AMA category 1 credits, CNE nursing credit hours, and continuing education credits for psychologists, and they’re completely free of charge on myCME.com. There’s a link in the description. I highly recommend you check them both out.
