Searching for Subclinical Atherosclerosis: Vascular Screening

I reviewed in a previous post  the importance of detecting sublinical atherosclerosis when trying to assess someone’s risk of heart attack and of dying suddenly.  Subclinical atherosclerosis refers to the build-up of plaque in the lining of our arteries which occurs long before any symptoms of atherosclerosis occur.

Since the process tends to be diffuse, occurring in all the large arteries of the body, it makes sense that if we can easily visualize one artery this will give us a window into what is happening in other arteries (including the coronary arteries supplying blood to the heart muscle).

Vascular Screening

The vascular screening I offer in my office uses high frequency ultrasound to image the large artery, the carotid artery, that supplies blood to the brain.

normalimtNormally the lining of that artery is smooth and thin as in the example to the left. As the process of atherosclerosis works its damage on the artery lining it becomes thicker and plaque begins to develop. High frequency ultrasound is an excellent tool for identifying these early, subclinical stages of atherosclerosis because it is painless, harmless, inexpensive, and quick. 

Identifying Higher Risk Patients

Mr. M is  a 60 year old man who I was seeing for an abnormal heart rhythm. Using the ACC risk estimator I calculated his 10 year risk of atherosclerotic cardiovascular disease (ASCVD) as <7.5%. However, he had a brother who had cardiac stents placed in his coronary arteries (indicating coronary artery disease (CAD)). His carotid artery screening (shown below) shows a large, soft plaque

Large, relatively echo lucent (soft) plaque found in the internal carotid artery of Mr. M.

This indicates that although his known risk factors for atherosclerosis were not tremendously high, the combination of known and unknown factors (likely genetic, given his brother’s premature CAD) were damaging the lining of his arteries leaving him at a  high risk for stroke and heart attack.

 

A patient like Mr. M I consider to have documented atherosclerotic cardiovascular disease (ASCVD)and I  will strongly recommend statin therapy along with a baby aspirin

Several studies have shown in those patients who are reluctant to start statin therapy, documenting subclinical atherosclerosis serves as a strong motivational factor for lifestyle change or compliance with medications.

Identifying Lower Risk Patients

Equally important as identifying advanced subclinical atherosclerosis, imaging the carotid artery can identify those patients who are at lower risk and save them from a lifetime of unnecessary treatment.

Ms N is 64 years old whom I see h for high blood pressure and supra ventricular tachycardia (an abnormal heart rhythm). She has a total cholesterol of 219, HDL(or good) cholesterol of 74, systolic blood pressure of 130 and the ACC risk estimator gives her an 8.4% risk of ASCVD over the next 10 years. She greatly dislikes taking medications, but her mother died in her early fifties from  a “massive heart attack” .

huelsingHer carotid exam shows the carotid thickness as less than average for her age and gender, equivalent to that of a 58 year old. There is no plaque anywhere in her carotid system. I feel comfortable not recommending statins to this type of patient. In many cases, I often  stop cholesterol treatment in patients with no evidence for subclinical atherosclerosis who have marginal cholesterol levels and intermediate risk.

What vascular screening allows me is the ability to see if my patients do or do not have the disease that we are trying to prevent or mitigate: atherosclerosis.

As the skeptical cardiologist I must point out that national guidelines do not endorse vascular screening primarily because there are no randomized controlled trials showing that it influences outcomes. I’ll talk more about potential pitfalls of vascular screening when done by for profit ventures in a subsequent post  and we’ll discuss the other good way of assessing for subclinical atherosclerosis: coronary calcium.

 

8 thoughts on “Searching for Subclinical Atherosclerosis: Vascular Screening”

  1. You are unbiased and evidence based but use an N=1 to support your screening practices with expensive tests that make you money?

    1. Great Question! It is basically getting at the problem of self-referral in cardiac testing. Money is a great motivator and many studies have demonstrated that cardiologists who own, for example, their own echo machines order a lot more echocardiograms on their patients. I think monetarily motivated self-referral contributes to over testing and increasing health care expenses.
      Personally, I have structured the price I charge for this testing ($34 for screening for carotid plaque) to be less than what Life Line Screening (a commercial, for profit vascular screening outfit) charges but enough to cover the expenses I have in the equipment and personnel. Most months I think a little more money comes in than goes out and my goal is solely to be able to offer good quality screening. . I only recommend the test if I think the information will change our approach.

      I’m not sure what you meant by N=1. I did present some case examples from my own practice of how useful the findings from vascular screening can be. However, studies have reported on the association of carotid plaque with CVD risk in over 50,000 subjects. This editorial from JAMA summarizes the studies which supported a Class IIA indication for carotid plaque assessment to aid in risk stratification in asymptomatic subjects (from the 2010 ACCF/AHA guidelines)

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