How Coronary Artery Disease Is Diagnosed

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Doctors can often assess coronary artery disease (CAD) risk with blood tests. In addition, doctors can diagnose mild, early-stage CAD with specialized diagnostic tests, such as an echocardiogram or angiogram.

However, the consequences of CAD include heart muscle dysfunction and alterations in heart rhythm. Doctors can more easily detect these conditions than early CAD. Often they are found by physical examination and tests of heart function.

When CAD is identified before it causes serious health consequences, the treatment can be more effective and prevent complications such as heart attacks and arrhythmias. 

This article explains which tests are used to diagnose CAD and other conditions that present with chest pain or shortness of breath.

coronary artery disease diagnosis
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Self-Checks

CAD does not produce symptoms in many cases, so it is not often easy to self-check for symptoms. However, if you experience concerning signs, don't dismiss them—it's important to bring them to your doctor's attention.

Though they may indicate another concern, the following symptoms could also point to CAD:

If you experience any of these or other symptoms you can't explain (such as shortness of breath at rest, palpitations, or dizziness), talk to your doctor and have a medical evaluation.

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Labs and Tests

Several tests can assess whether you have a high likelihood of developing (or already have) CAD. In general, these tests do not directly identify CAD, but they can identify its causes. 

Blood Pressure

Hypertension is among the leading causes of atherosclerosis (arteries narrowed by plaque) and CAD. Fortunately, hypertension is relatively easy to check for using a blood pressure cuff.

Usually, if your blood pressure is normal at the doctor's office, there is no reason to worry about hypertension. But if it is high, that could be a false reading that needs to be verified since some people experience "white coat hypertension," which is an elevated blood pressure related to anxiety in a medical setting.

Electrocardiogram

An electrocardiogram (EKG) is a non-invasive electrical test that can look for evidence of heart muscle weakness and heart rhythm irregularities. There are many causes of EKG abnormalities, and damage to the heart due to CAD is among them. 

Blood Cholesterol and Triglyceride Levels

High blood cholesterol and triglyceride levels can indicate that you have CAD or are at risk of developing CAD.

Blood Glucose Levels

High fasting blood sugar levels can mean that you have diabetes. Depending on your results, you may need another test called a hemoglobin A1C test.

This test assesses your blood sugar levels over a period of months. Blood glucose levels can determine whether you have diabetes, which is among the causes of atherosclerosis and CAD.

Recap

Some labs and tests can help your doctor determine if you are at risk for CAD or already have it. These include certain blood tests, blood pressure tests, and EKG.

Imaging

Imaging tests can be especially helpful in diagnosing CAD. This is because these tests can examine the structure and function of the heart. Traditionally, the diagnosis of CAD has relied on tests that look for evidence of significant blockages in the coronary arteries.

In general, cardiologists consider a significant blockage to be one that obstructs 70% or more of an artery's channel.

Cardiac Stress Testing

Often, people with CAD have alterations in heart function when the heart undergoes increases in demand. Stress testing is often helpful in diagnosing partially blocked coronary arteries.

In a cardiac stress test, your doctor checks your heart functions under increased demand in a controlled setting. For example, you may be asked to exercise or be given medication.

While most are familiar with an EKG being used to monitor heart function, an imaging test, such as an ultrasound, may be used during the test to see how your heart responds when demand increases. A nuclear stress test can also help provide more detailed imaging.

Controlled stress testing can often bring out symptoms of angina (chest pain as a result of lack of oxygen to the heart). They can also reveal characteristic changes on an electrocardiogram or echocardiogram—findings that strongly suggest blockages are present.

Echocardiogram

An echocardiogram is a non-invasive imaging test that uses ultrasound to observe your heart in action. With this test, your doctor and technician can assess:

  • The pumping of your heart from different angles
  • Heart muscle function
  • Valve function
  • Pressures in the heart

Thallium/Technetium Study

Thallium and technetium are radioactive substances that are injected into a vein during exercise. These substances are carried to the heart muscle by the coronary arteries, thus allowing your doctor to view the heart with a special camera.

If one or more coronary arteries are partially blocked, the areas of the heart muscle supplied by those arteries show up on the image as dark spots. 

Multislice CT Scan and Cardiac MRI

Computed tomography (CT) scans and cardiac magnetic resonance imaging (MRI) are both noninvasive imaging tests that can assess the anatomical structure of the heart. Doctors may use them to give them more information about your CAD, specifically for treatment planning.

Calcium Scans 

Calcium scans are emerging as a useful way of detecting the presence of even small amounts of CAD. Calcium scans are a form of CT scanning that can quantify how many calcium deposits are in the coronary arteries.

Since calcium deposits generally occur in plaques, measuring the amount of calcium in the arteries can tell your doctor whether CAD and plaques are present. It can also help determine how extensive the CAD may be. 

Angiogram

An angiogram is an invasive diagnostic procedure where your doctor places a catheter (tube) into your blood vessels while they examine your chest with an X-ray or ultrasound. This test evaluates how well the blood vessels fill with blood and whether there is any obstruction. In addition, this is a direct way to view the structure of the coronary arteries. 

Recap

Imaging tests allow your doctor to see whether there is a blockage in your arteries and, if so, how much. The imaging tools used for these tests include ultrasound, CT scans, and MRI. In addition, some involve the use of catheters and dyes.

Differential Diagnoses

Other medical conditions can manifest with chest discomfort or shortness of breath. Some of these conditions, like CAD, also require medical management.

Your medical history, including the frequency, progression, and duration of your symptoms, generally helps your doctors decide which diagnostic testing to use.

In general, a heart attack is considered the most serious of these diagnoses. So, if you have symptoms suggestive of one, your doctors will rule that out with an emergency EKG before moving on to testing that is more tailored to your symptoms. 

It is also possible that you could have CAD in addition to one of the following conditions. 

  • Gastroesophageal reflux disease (GERD): Often described as heartburn or indigestion, GERD can cause pain and discomfort typically associated with eating, particularly after eating spicy foods. The burning pain of GERD tends to worsen with lying down and is not closely associated with stress and physical exertion the way symptoms of CAD are. 
  • Asthma: Characterized by sudden and severe episodes of shortness of breath, asthma typically begins at a young age. It can be difficult to know whether your shortness of breath is related to asthma or CAD. If you experience this symptom, seek emergency medical attention until you have a diagnosis and a treatment plan.
  • Chronic obstructive pulmonary disease (COPD): Disease of the lungs causes shortness of breath, which typically worsens with exertion. Your doctor can distinguish between the conditions with a physical examination and diagnostic tests.
  • Aortic stenosis: The aorta is the largest blood vessel in the body, sending oxygenated blood from the heart to the rest of the body. Narrowing of the aorta is a serious condition that can cause low energy, chest pain, and even loss of consciousness. Diagnostic tests can differentiate between aortic stenosis and CAD.
  • Anemia: A condition in which the red blood cells do not function as they should, anemia is characterized by low energy. If you have anemia, it can be diagnosed with a blood test. 

Summary

Your doctor may diagnose CAD in a number of ways. These may include blood tests, blood pressure tests, and EKG. If these tests indicate CAD, further imaging tests may be necessary.

Not all chest pain and shortness of breath are related to heart disease. However, since CAD is serious, it's important to get it checked out to be sure. Other conditions that share some symptoms include asthma, GERD, COPD, anemia, and aortic stenosis.

Frequently Asked Questions

  • What is the most common cause of CAD?

    CAD is usually caused by atherosclerosis, which is the build-up of plaque consisting of cholesterol and fatty deposits in the inner walls of the arteries.

  • How quickly does CAD progress?

    In most cases, CAD progresses gradually over many years as the coronary arteries narrow with plaque over time. Then a heart attack may suddenly occur if a plaque ruptures and causes a blood clot, blocking blood flow through that artery.

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