How is coronary artery disease (CAD) diagnosed?

The gold standard for the diagnosis of coronary artery disease is the coronary angiogram, a term often used synonymously with cardiac catheterization.

During this procedure, which is performed in the cardiac catheterization laboratory, a tube or catheter is inserted into a blood vessel (usually in the groin), and is guided to the heart with the assistance of x-ray imaging. Dye is then introduced into the coronary arteries to detect blockages, and digital cine films (angiograms) are recorded and analyzed.

The appropriate use of imaging tests to diagnose coronary artery disease (CAD) depends on the situation. For apparently well people without heart symptoms, I do not favor the use of any imaging test for screening for CAD.

For individuals with symptoms suggestive of CAD, a stress test monitored by electrocardiogram is often a good place to start. For those without symptoms but at high risk for CAD based on non-imaging markers, imaging tests may provide useful information for management. You should discuss with your cardiologist about whether you fit into this category.

Computed tomographic angiography of the heart (coronary CTA) is evolving rapidly and may become part of routine practice in those with symptoms, elevated calculated risk, or a positive stress test. Currently, the level of radiation is on the same order as a cardiac catheterization with traditional invasive angiography. Technical advances are rapidly lowering the amount of radiation required for coronary CTA. Even so, such tests should not be used for routine surveillance on a repetitive basis.

An EKG can be very useful for a doctor to notice when the blood supply is constricted. Still, an EKG in someone with a history of Coronary Artery Disease and angina often has a "normal" reading.

Because a resting EKG often produces a "normal" reading for someone with angina, doctors may need to perform a stress test to evaluate the presence of Coronary Artery Disease. If characteristic signs occur during stress testing, especially if typical chest pains occur, the test is considered "positive".

A cardiac catheterization test can determine if Coronary Artery Disease is present, how severe it is and if a coronary artery bypass graft is needed. The catheterization test can definitely exclude Coronary Artery Disease if it is not present.

A doctor will perform the test if:

• angina is being treated by a doctor by the symptoms continue
• severe blood flow restriction is present on a stress test and symptoms suggest Coronary Artery Disease, yet the doctor is not able to come to a definitive diagnosis with other tests
• a patient has many hospital admissions for chest pain where a heart attack is ruled out but the presence of Coronary Artery Disease has not been determined

During cardiac catheterization, blockages are treated by a balloon that is blown up inside the coronary arteries, forcing open the passage. This procedure is Percutaneous Transluminal Coronary Angioplasty - or just plain angioplasty.

Doctors can determine your risk for CAD by checking your blood pressure, cholesterol and blood glucose, and by finding out more about your family's history of heart disease. If you're at high risk or already have symptoms, your doctor can perform several tests to diagnose CAD, including ECD or EKG (electrocardiogram), echocardiogram, exercise stress test, chest X-ray, cardiac catheterization and coronary angiogram.

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 If the heart muscle cannot get enough oxygen—a state known as myocardial ischemia—symptoms such as chest pain (angina) or shortness of breath may result.
 
A presumptive diagnosis of coronary disease is based on a review of symptoms, health history, an electrocardiogram, and an exercise stress test, perhaps with a thallium scan. A more definitive diagnosis requires cardiac catheterization and angiography.

During an exercise stress test, the patient is hooked up to an electrocardiographic monitor (an EKG machine) and then asked to walk on a treadmill, peddle a stationary bicycle, or climb steps. The EKG monitor will show whether the heart muscle is getting enough blood. An exercise test also detects silent ischemia, a condition with no symptoms in which the heart muscle does not get enough blood.

If severe narrowing is suspected, a coronary angiogram may be needed. This examination entails threading a catheter through a blood vessel into the heart, and then injecting a dye into the coronary arteries to make them visible on x-rays.

To determine whether you have coronary artery disease, and how severe it is, your doctor will talk with you about your health, lifestyle and family history. This information, plus the results of a physical examination and blood tests will help determine whether you have risk factors for heart disease.

Your doctor may also want you to have certain diagnostic tests, including one or more of the following:

• electrocardiogram, which measures electrical activity in your heart;
• a stress test, which measures your heart’s ability to tolerate exercise  and may include an imaging test as well; and
• cardiac catheterization (also known as coronary angiography) or computed tomography, both of which allow your doctor to see images of your arteries and any build up of artery-clogging plaque.