Searching for Subclinical Atherosclerosis: Vascular Age

I’ve discussed in a previous post the importance of detecting subclinical atherosclerosis.

The process of atherosclerosis (the build up of fatty plaques in all arteries) occurs silently and often the first symptom is sudden death due to a heart attack.

Examining the large arteries in the neck (the carotids) with ultrasound for early fatty  plaques helps establish whether atherosclerosis is present or not.

If there is plaque in the carotids this is a strong indicator that atherosclerosis is present throughout the large arteries of the body including the coronary arteries supplying blood to the heart.

Ruptured plaques in the coronary arteries are what cause heart attacks and most cases of sudden cardiac death are due to heart attacks.

If we can identify those who have subclinical (i.e. before significant blockages and symptoms develop) atherosclerosis, we can better target aggressive therapy to those at the highest risk.

Carotid IMT: The window to your vascular age

There is a second technique which uses carotid ultrasound  available to evaluate an individual’s longer term risk of heart disease even before plaque develops.

This technique is termed carotid IMT. IMT (intimal-medial thickness ) refers to the thickness of the wall of the artery which includes the thin layer of cells lining the inside of arteries or intima and the smooth muscle in the wall of the artery (media).

The Carotid IMT has been shown to be related to all of the risk factors that medical science knows for atherosclerosis. It progressively increases with normal aging and we have data on what the normal value is for white and black  men and women between the ages of 40 and 70.

By making multiple precise and careful measurements of an individual’s CIMT we can determine where that individual stands in comparison to normal individuals of the same age, gender and race.

Individuals whose CIMT is great than that of 75% of individuals of the same age and gender are at significantly higher risk of heart attack and stroke even if no carotid plaque is discovered.

Thus, the CIMT serves somewhat as an early warning signal for unhealthy arteries.

We can also determine a so-called vascular age from this technique.

 

Carotid IMT is the distance between the lines the two arrows point at
Carotid IMT is the distance between the lines the two arrows point at

An example of this is shown to the left. . The individual was an asymptomatic young man. He had no plaque but his CIMT measured 0.770, which is significantly higher than the normal CIMT for a similarly aged white male of 0.598.  This is thicker than 80% of normal individuals of the same age and gender. It is normal for an individual who is 65 years old. Thus, this individual’s vascular age is 65 years, 20 years greater than his chronological age.

In my office I usually recommend a combination of CIMT and carotid plaque be performed in individuals in whom I am trying to assess risk of cardiovascular disease between the ages of 40 and 70.

There is no reason to do CIMT in patients who have documented coronary heart disease (heart attack/stroke/stent/bypass surgery), carotid disease (stroke/carotid surgery), or peripheral arterial disease. These patients have already passed the early warning phase of atherosclerosis.

This technique should only be done by physicians/technicians who have been adequately trained and have dedicated themselves to performing the meticulous tiny measurements required in an accurate manner.

Major cardiovascular organizations differ on recommending  CIMT for screening purposes.  Well-respected scientific papers have clearly established CIMT as reproducible and highly predictive of vascular events but there is no randomized , controlled trial which establishes that utilizing it in conjunction with treatment decisions based on the results will improve cardiovascular outcomes.

For this reason, even though it is cheap, painless, harmless and quick insurance companies do not reimburse for the costs.

Some caveats:

*We don’t have good data sets on individuals under the age of 40 years. I offer CIMT to this group and extrapolate the good data  but more studies are needed in this age range.

*We don’t have good data sets on ethnicities other than the African-americans and European and American whites.

*Multiple methods of CIMT recording and measurement  have been published.

*I don’t find CIMT useful in individuals over the age of 70. Carotid plaque is much more helpful. Most men have carotid plaque by this age. If you don’t have any carotid plaque over the age of 70 years then you are in a very low risk category and are unlikely to benefit from statin or aspirin therapy.

Next post we’ll discuss the third noninvasive tool at cardiologists disposal to assess individuals for subclinical atherosclerosis: a direct look at calcium in the coronary arteries

N.B. As noted here.

The full process underlying intimal thickening is not fully understood but is thought to be similar, though not identical, to that underlying atherosclerosis. The hypothesis that IMT represents subclinical vascular disease may be supported by the finding of graded associations between IMT and concurrent atherosclerotic change visualized in the coronary arteries during angiography. It is important to note, however, that whilst in many cases thickening of the intima–media does represent atherosclerotic change, in other cases it may represent non-atherosclerotic lesions such as hypertrophy in response to shear stress on the artery wall.

 

 

 

 

 

 

 

 

5 thoughts on “Searching for Subclinical Atherosclerosis: Vascular Age”

  1. Would you recommend CIMT for a person in there 30’s with a diagonal earlobe crease? I read a study recently where everyone with a diagonal earlobe crease had a significantly higher CIMT measurement. I am in my mid 30’s and have a diagonal crease and have been wondering if I have subclinical atherosclerosis, but I’m afraid to ask a doctor since the earlobe crease seems voodoo like.

    1. I must admit I haven’t thought about the diagonal ear lobe crease (ELC) for decades. It was mentioned in my early training years but seemed to have fallen by the wayside since then.
      Prompted by this comment I briefly looked at the literature on ELC as a predictor of coronary heart disease. There are over 50 papers on this with varying conclusions but a recent review er felt that ELC was an independent risk marker.
      I’ll probably put out a more detailed post on this down the line.
      For now my recommendation would be to consider the presence of ELC as equivalent to a family history of coronary heart disease.
      You would be advised to be more vigilant about the known modifiable risk factors: don’t smoke, exercise regularly, maintain ideal body weight and monitor cholesterol levels.
      Consider vascular screening and/or coronary calcium scan to assess for subclinical atherosclerosis.
      I’m a little leery of CIMT in subjects in their 30s as we have very limited data in this age range. The vascular screening would be more valuable for detecting plaque which would put you in a really high risk group. Similarly, if any calcium was detected by coronary calcium score your risk would be high at this age.
      I don’t know how the crease is voodoo like. The crease, itself, is just an innocent bystander.

      1. Thanks for your reply. I don’t have any risk factors, in fact, my cholesterol has never been above 135. Right now my HDL is 45 and my total is 105, triglycerides are usually around 35. This is all without medication. Also have never smoked, but don’t exercise regularly. I have Gilbert’s Syndrome which has been linked with a much lower chance of cardiovascular disease. And I’m tall, which has been linked with lower chance of cardiovascular disease. But I can’t shake this earlobe crease thing. It just has me freaked out!!

  2. Hi Dr. Pearson, I ended up getting an IMT screening at St Lukes last Thursday and it looks like you are who read the test and gave the results! Right IMT 0.43 and right IMT 0.50. It says 30th percentile for age and gender (36 and Male), so I guess the earlobe crease may not mean much for me, at least not right now.

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