I reviewed in a previous post the importance of detecting subclinical 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).
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.
Normally 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
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” .
Her 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.