Screening for Coronary Disease

Screening for Coronary Disease is not what most people think.

Coronary artery disease is the most common cause of death in the United States and the world. Briefly, when someone has a heart attack, it is due to coronary disease. Cholesterol plaques are deposited in the lining of the coronary arteries, which deliver blood to the heart itself. This causes inflammation and damage to the arteries, and clots can form. When the clot occludes the flow of blood, a heart attack can occur, causing damage to the heart muscle and sometimes dangerous and fatal heart rhythms. Even if complete occlusion doesn’t happen, narrowing of the arteries can cause chest pain and weakness of the muscle, leading to heart failure.

Unfortunately, many people have no idea that they have coronary disease until damage is done. Sometimes, the first sign of the disease is sudden death from a heart attack or arrhythmia. Like most conditions, we would like to diagnose coronary disease early, while there is time to prevent the dangerous signs and symptoms.

Most people do not know what it means to screen for coronary disease. They think that the doctor listens to their heart, checks their cholesterol, and they’re good to go. That is not what I’m talking about. Listening to the heart does not detect early or even late coronary disease in most cases. Checking cholesterol levels is extremely important, but cholesterol levels are a risk factor for heart disease, not heart disease itself. There are many risk factors for coronary disease: cholesterol levels, diet, smoking history, family history, body weight, body fat distribution, and others. Even if you have multiple risk factors, you may never develop the disease, and some people with coronary disease have few if any risk factors.

Sidenote: I have heard people say many things about cholesterol. One is that they don’t understand how they had a heart attack since their cholesterol is fine. A similar statement is that they aren’t going to have a heart attack because they have normal cholesterol levels. Elevated cholesterol is a risk factor for heart disease, and treatment to lower cholesterol lowers the risk of heart disease. (This is definitely true, and anyone who says otherwise is mistaken or lying.) But people can have heart disease without having an elevated cholesterol. Risk factors are just that.

This is true with many conditions. Family history of breast cancer is a risk factor for breast cancer, but most women with breast cancer have no family history. Many people involved in serious car accidents are good drivers with a spotless record and no prior history of accidents. While most cases of lung cancer are in smokers, not all are. During my career in medicine, I saw many, many cases of coronary disease in people who did not expect it.

So, how do we screen? A person’s risk of a disease affects how we screen for it. For example, a teenager has an exceedingly low risk of prostate cancer, so we don’t screen at all. The same is true for breast cancer. Most young women should not be screened for breast cancer. People at very low risk don’t need screening. People who already have proven coronary disease need testing, but not the screening tests that we are going to talk about.

Let’s look at specific types of people. First would be people who are at very low risk and should not get screened. Tests are not perfect. Since a young, healthy person with no risk factors for heart disease (no family history of disease at a young age, and no genetic cholesterol problem) has such a low risk, false positive tests would actually outnumber any positive tests that were real.

We often screen people without symptoms who want to start an exercise program. They or their doctor may want to make sure they are safe to participate. A stress test may be a good choice. The patient walks on a treadmill in a standardized, progressively more difficult protocol, while an ECG is running. Sometimes, an ultrasound (echocardiogram) or nuclear imaging test is also performed. Certain changes on the ECG or imaging would indicate an increased risk of the patient having diseased, narrowed arteries. Further testing, such as a coronary angiogram, would then be performed to determine the extent of disease and whether treatment is indicated.

People with no symptoms but who are at significantly elevated risk may not need screening. They are so likely to have coronary disease that the doctor could just assume that they do have it. For example, they may have a markedly elevated LDL cholesterol and multiple family members with coronary disease. Aggressive risk factor modification would be instituted without further testing. This includes good blood pressure control, cholesterol-lowering medication (typically a statin such as rosuvastatin, which I take), and an exercise program. A stress test might be performed, as mentioned above, to see if they can tolerate such a program.

Perhaps the most common type of patient to screen is one where the risk of disease is intermediate. They may have a family history, but the cholesterol is not markedly elevated. A smoker without a family history may fit in this category. Here, a stress test would not be good enough. Remember, a stress test only detects advanced disease. A routine ECG would be of little help and is not recommended to screen for coronary disease, because there are many false positives and negatives. In this patient, a coronary artery calcium scan may be best, and it was the test I preferred when I was in practice.

The scan itself is simple. You lie in a machine for a few minutes. It is not enclosed like an MRI, and I have never heard of anyone becoming claustrophobic. There are no injections and essentially no risk. When cholesterol plaque is deposited, it is soft and uncalcified. Over time, the plaque calcifies, and you can see it on the scan. You will get a numerical score reflecting how much calcium is found in the lining of the arteries. The best is zero. That means that you have no detectable calcification in the coronary arteries. The percentile tells you how you compare to others your age.

A low score when you are young may be in a high percentile. That same score when you are older will put you in a lower percentile. If you are under 50, most people have a zero score. That could be because there is no plaque, but it could also mean that it is there but hasn’t calcified yet. Some specialists would recommend repeating the scan every five years or so until you are 60, giving the plaque time to become visible.

The calcium score scan doesn’t tell you if the arteries are narrowed, though the higher the score, the more likely it is that there is some narrowing. Even without narrowing, plaque can cause a heart attack, but narrowing makes heart attacks more likely. If your doctor suspects narrowing, they may order a stress test or a CT angiogram, a more detailed scan that shows narrowing. The CT angiogram is more expensive than the calcium scoring and requires injection of a contrast agent and more time in the scanner. The CT angiogram is not an appropriate screening tool for most people.

I found the calcium score test to be very helpful. For example, if you are 50, one of your parents had a heart attack in their 50s, but your cholesterol is fine, and you have no other risk factors for heart disease. You might consider a scan. If there is no plaque, your doctor may just repeat the scan in five years. If there is plaque, they may recommend a change in diet and start a statin to slow or prevent further plaque deposition. Statins reduce the risk of a heart attack and save lives.

Everyone wants to have a longer, healthier life, but we all want to live life to the fullest. Many people watch their diet and exercise, but otherwise ignore their risk of the most common cause of death. Talk to your doctor about screening for heart disease. Maybe you haven’t reached the age where any specific screening is needed. If screening is considered, ask if a calcium score is a good idea.