“Why would I ever care about heart attack screening, Jake?” This is a reasonable question so let me put it this way:
The ACS [American Cancer Society] recommends the following screening ages: 20 for breast cancer with mammography from age 40 (at least annually), 21 for cervical cancer (Pap test), 50 for colorectal cancer (several options), and 50 for prostate cancer (prostate-specific antigen test and digital rectal examination annually).
What do we recommend for heart attacks? Well, basically we recommend that, unless you have some very serious risk factors, you wait until you have a heart attack that might kill you. Then come talk to us about treatment.
OK so maybe I am being a little tongue in cheek, but there is a point to this. In comparison to almost every other potentially fatal medical condition, heart attacks are the only one where we do not do a screening test that involves imaging. Basically, if you are getting older you go to your doctor, and they ask you whether you have cardiovascular risk factors like diabetes or high blood pressure. They also check your cholesterol. They do not check whether you actually have atherosclerotic plaques on your arteries — even though we know that these suggest that you are at high risk for a heart attack. Think of this in comparison to colon cancer where the recommendation is that you receive a colonoscopy every ten years after age 50.
It is in this context that the Association for the Eradication of Heart Attack has issued the SHAPE (Screening for Heart Attack Prevention and Education) guidelines for screening against heart attacks.
These things are always really Mandarin, so I thought I would break them down for you.
It works like this. If you are a male age 45-75 years or a female age 55-75 years, you are eligible for screening. These rules do not apply you if you fall into one of the following categories:
— Over age 75. (Then we treat you automatically.)
— Have none of the following risk factors: Chol>200 mg/dl, blood pressure >120/80 mmHg, diabetes, smoking, family history, and metabolic syndrome.
— No history of angina, heart attack, stroke, or peripheral arterial disease. (If you have such history, we need to treat you already.)
— You are younger than the ages listed above. (We’ll get to you when you are older.)
If you are eligible for screening, what would happen is that you would be immediately subjected to one of the following to screens for atherosclerotic plaques:
— Coronary artery calcium (CAC) determined by CT
— Carotid intima-media thickness (CIMT) and plaque determined by ultrasonography
Just so you don’t freak out on me, you should know that neither of those are at all like colonoscopy. Rather a CT is like a 3D X-ray — over in 30 seconds and all you have to do is sit still. A ultrasonography is exactly the same technology they use to look at babies in the womb — you just get covered in this weird goo. but it is over quick.
Both of those imaging modalities were selected because they were deemed cost-effective, relatively sensitive and precise, and non-invasive. They are not the only things on the market, and over time the recommendations indicate that others may be used if they are become better than these.
What happens to the data from those tests? If you are determined to have no or little atherosclerosis (i.e. the test is negative), the doctor will ask you about your risk factors again. If you have no risk factors, then you are low risk. The level of cholesterol that you need to keep below is relatively high (160 mg/dL), and we only need to see you again in 5 to 10 years. If you have some risk factors, then you are moderate risk. You need to have a slightly lower cholesterol (130 mg/dL), but again we only need to see you every 5 to 10 years.
If you are determined to have atherosclerosis — depending on how much — a variety of things could happen. First, depending on how much you have, the amount of cholesterol you need to keep below gets progressively lower. Also, for individuals who have particularly prominent atherosclerosis, you may need to have a stress test and possible some interventional radiology to deal with the blockage. Also, we need to see you more regularly.
The purpose of all of these guidelines — like colon, prostate, or breast screening — is to prevent disease before it happens. The guidelines are intended to minimize risk while limiting the cost of all the screening. How do these guidelines measure up on that front? Well the authors claim that by their calculations, the implementation of these guidelines should save about 21.5 billion dollars a year over the cost of performing the screening in terms of reduced interventions and hospitalizations. It could also save as many as 90,000 lives a year.
So there you go. For physicians who would like a more exact flow chart of the screening guidelines click on the image below. For all of us, especially if you are in the eligible group described above, talk to you doctor so that you can limit your risk of heart attack.