CIMT Testing: The Ultimate Guide to Measuring Your Heart Attack Risk
By: Dave Asprey
I’m honored to publish this guest post by my friend Dr. Philip Lee Miller, MD, founder and director of the California Age Management Institute. Dr. Miller was the first anti-aging physician to run a comprehensive anti-aging panel on my blood more than a decade ago, and for years has been a frequent attendee of the Silicon Valley Health Institute, the non-profit anti-aging group I have helped to lead for 10 years.
Dr. Miller is also the first physician I called for help when my father had a heart attack years ago. (Dr. Whitaker was the second!) This is a really informative post and I’m grateful Dr. Miller took the time to share it. You can see him at his clinic in Los Gatos, CA.
Cardiovascular disease (of heart and blood vessels) is still one of the leading causes of death and disability in the United States. What are the risk factors for heart attack or stroke? In what way can we quantify or measure these risk factors? What are the testing methods that are available for us?
CIMT testing, or ‘carotid intimal medial thickness’ testing, is a new and powerful approach that is simple to administer, involves non-ionizing radiation, and is 88-92% correlated with cardiovascular disease – much more accurate than most commonly used baseline cardiovascular tests today.
Cardiovascular Risk 101: A Primer
Cardiovascular risk can be measured from multiple aspects. We can quantify genetic and family risk. We can quantify nutritional risk. We can quantify functional, electrical, structural, vascular and rheologic (blood flow turbulence) aspects of cardiovascular risk. Even emotional and psychological stress can promote cardiovascular risk. Dean Ornish maintains that “disconnectedness” (social isolation) is the major cardiovascular risk. But so far there is no one single test – biochemical or otherwise – that is a sole predictor. It is a constellation and interpretation of these multiple factors.
Briefly, an initial comprehensive cardiovascular workup might include some or all of the following:
- Stress treadmill
- Stress 2-D echocardiogram (ultrasound) looking at the structure of your heart
- Dual isotope (nuclear medicine) heart scan looking at the functional and metabolic (flow) characteristics of your heart
- Superfast CT scan (EBCT scanner) looking at coronary artery calcification scores.
Then, these would be followed by a very comprehensive cardiovascular biochemical panel to include:
- Triglycerides (exacerbated by high carbohydrate intake)
- LDL – transports cholesterol to the heart (misnamed bad cholesterol)
- HDL – transports cholesterol away from the heart (misnamed good cholesterol)
- Lp(a) – causes hardening of the arteries
- LpPLA2 – measures inflammatory aspects of LDL
- CRP (C-reactive protein measuring inflammation – measures inflammation)
- Fibrinogen – measures inflammation
- Pattern A (large fluffy LDL particles) or pattern B (small dense LDL particles) typing.
The list grows each year. The current cutting-edge approach is measuring total numbers of LDL particles rather than LDL concentration.
Over the years, increasingly sophisticated approaches to quantifying cholesterol have been implemented including HDL, LDL, VLDL. This has been superseded by more recent particle quantification tests from Liposciences. So if you believe cholesterol is the culprit, Liposciences may be the most sophisticated approach.
But traditionally the only valid correlation between all these risk factors and the true development of coronary artery (heart vessels) has been coronary angiography angiography. This is where a large catheter is inserted into the femoral (groin) artery, snaked retrograde through your aorta into the heart visualizing your coronary (heart) arteries. This is fraught with many complications including bleeding and too many unnecessary procedures such as stents. The basic sentiment has been, “while we’re here we might as well do something.”
Beyond Cholesterol: What Else Is Going On Here?
Over the past 50 years you have been admonished to cut your fat intake and reduce your cholesterol intake. Even as a child I remember the ads and social programs promoting margarine over butter. We now know that margarine is literally bottom of the barrel of hydrogenated oils – probably the worst. Animal studies and large human studies have previously concluded that cholesterol and fat are the primary source of cardiovascular risk. But is this true? And what type and source of fat if so?
One of the most astute lecturers I know has been quoted as saying, “cholesterol — found at the scene of the crime, not guilty.” This is quite apt as cholesterol is a poor prognosticator of heart disease. The famous Framingham study of the past 50 years shows that at least 50% of those who had heart attacks had “normal cholesterol values.” See image 1:
But missing from the cholesterol theory is the effect of triglycerides and carbohydrates as risk factors. Carbohydrates and high triglycerides have never been proven to be cardiovascular risk but the evidence is accumulating. Tim Russert, the former host of Meet the Press, died with entirely normal cholesterol … and very high triglycerides.
In fact the list of potential risk factors dwarfs cholesterol:
- Hypertension (high blood pressure)
- Tobacco use
- Raised blood glucose (diabetes)
- Physical inactivity
- Unhealthy diet
- Overweight and obesity
- Advancing Age
- Family history
Even more graphically to illustrate just how complex (and daunting) cardiovascular risk assessment can be:
Enter CIMT (Carotid Artery) Imaging: Why CIMT?
Clearly the variety of traditional and non-traditional risk factors at play makes this a complex puzzle: so what does CIMT testing add to this conversation?
CIMT testing, which is FDA approved and will be gaining favor over the next five years, matches actual real disease, not population based statistical probabilities. It measures your own individual risk. It looks at vascular plaque development and the arterial wall thickening that correlates with arterial disease. (See diagram below.)
Imaging is all about visualizing actual disease or dysfunction and then reconciling it with a set of traditional cardiovascular risk parameters.
Other advantages of CIMT testing include the following:
- It is rapid: a typical exam takes about 10 minutes followed by a 10-15 minute explanation and interpretation session.
- It is non-invasive.
- It is non-ionizing (no x-rays).
This type of testing is useful because a patient could have totally normal cholesterol values with developing disease; on the other hand, a patient could also have high cholesterol with no evidence of vascular disease. That is what we aim to prove and show to you.
What the Actual Imaging Shows
The testing starts with ultrasound plaque identification followed by the measurement of the two inner layers of your carotid artery: the very thin intima (inner lining) + media (muscular layer of the artery). You can see by the diagram below that increasing thickness is associated with increasing disease of the artery.
The thickening yellow portion of this diagram illustrates increasing inflammatory response. It is a progressive accumulation of white blood cells and inflammatory cells. Cholesterol participates in this process. But it is not the cause of the disease.
In a most graphic sense, it represents an abscess of your arterial wall. At the end of this progression the thin fibrous cap ruptures. This rupture is followed by an immediate aggregation of platelets, which forms a clot. This clot (thrombosis) = heart attack or stroke.
The goal is to identify the early stages of this process, not the late stages. That is your primary interest – identifying early disease and preventing the progression to late stage catastrophe.
It also incidentally measures progressive changes that results from high blood pressure. It has an 88-92% correlation with heart disease — the coronary arteries. See image:
What To Expect: The Final Image
After a brief exam, here’s an example of what the results would look like (image below).
You will see the cross section looking for plaque and the longitudinal section as shown above to measure the CIMT width. Flow rates can also be included as a traditional measure looking for any signs of obstruction to vascular low. This is based on Bernoulli’s principle that smaller and smaller diameters of a pipe (artery) have increased flow rate, so that conversely low flow rates are diagnostic of clear open (patent) carotid artery.
These results can be interpreted and explained in under fifteen minutes – let us show you how it works.
About The Author:
Dr. Philip Lee Miller, MD, is Founder and Director of the California Age Management Institute located in Los Gatos, California. California Age Management Institute is the only center in the San Francisco Bay Area to offer true CIMT testing at this time. You can learn more or book your appointment today by visiting the website or calling 408-358-8855.