Coronary artery disease (CAD) is the most prevalent disease in the United States, causing 650,000 deaths each year.
What is CAD?
CAD develops when fatty deposits, debris, calcium, and cholesterol accumulate in the wall of the blood vessels supplying the heart muscle. These areas are called plaques. Some plaques have a thinner wall, which makes them more prone to rupture, and are called vulnerable plaques (Figure 1).
If a plaque ruptures, the debris inside can cause a clot to form which can block one of the arteries supplying the heart muscle. The decreased blood flow to the heart muscle is what is called a heart attack and, if severe enough, can cause sudden death. If the ruptured plaque does not block the blood vessel, the plaque may heal by hardening or calcifying. This can narrow the blood vessel, which decreases blood flow to the heart muscle but less severely than when a clot suddenly blocks the vessel.
In the early stage of CAD, there is often little or no narrowing of the coronary blood vessels, so traditional angiography, which looks for a blockage or narrowing of the coronary arteries, may not detect the condition. For these patients, the first and only symptom of CAD they may experience is a massive, fatal heart attack.
Chest pain, shortness of breath, and fatigue, especially with exercise, are common symptoms of narrowing of the coronary arteries, and it is this later stage of CAD that is often detected by traditional angiography. Millions of patients diagnosed with CAD are managed medically, at a cost of more than $30-billion annually.
How Coronary CTA helps
Coronary CT angiography is the best non-invasive test available for looking directly at the coronary arteries (Figure 2 and 3).
With Coronary CTA, we not only see narrowing of the coronary arteries, but also see the plaques in their early stages. Coronary CT angiography has been shown to be 95% sensitive in detecting CAD, and to have a 98% accuracy rate in ruling out the disease.
In most cases, angioplasty (a procedure that reopens blocked vessels) and/or stenting is not indicated until a coronary artery is narrowed by as much as 70%. Even so, it is important to identify early stage CAD because it can alert a physician that there is a need to prescribe statin drugs. (i.e. Lipitor, Crestor, etc)
Statin drugs speed the maturation of plaques, making them less vulnerable to rupture. These drugs have been shown to decrease the risk of heart attack in high risk patients by more than 50%. They also decrease the risk of heart attack for patients with normal cholesterol levels by approximately 20%.
Who should be tested with Coronary CTA?
Coronary CT angiography may be indicated when a patient has one or more of the major risk factors for coronary disease.
These risk factors include:
- Current tobacco use
- Hypertension (>140/90)
- Elevated LDL (>130)
- Low HDL (<40)
- Strong family history of CAD
- C-reactive protein, inherited syndromes
Contraindications for Coronary CTA include:
- Lack of risk factors
- Allergy to the contrast agent if medications fail to control the reaction
- Atrial fibrillation
- Kidney failure
Preparing for a Coronary CTA
Patients preparing for a Coronary CT angiogram should avoid caffeine in any form (caffeinated coffees, teas, soft drinks, etc.) for 12 hours prior to the exam, and should take no solid food for 4 hours prior to the exam. Prior to the test, the patient will receive one dose of a beta-blocker. An intravenous (IV) line will be placed, and a contrast agent will be delivered through the line. A single dose of nitroglycerine spray will be given under the tongue.
What to expect during a Coronary CTA
During Coronary CT angiography, the patient lies quietly on a table that moves through a doughnut-shaped machine called a "gantry." As the patient moves through the gantry, an x-ray beam and x-ray detector rotate around the patient, creating a series of cross-sectional images of the heart and the blood vessels supplying it. The patient will be asked to hold his or her breath several times while images are obtained. The last part of the exam, when the most important images of the heart are obtained, is usually acquired in just 5 heartbeats. The cross-sectional images are transferred to a computer that uses specialized software to "reassemble" the cross sections, delivering a multidimensional view of the coronary arteries. Because of the contrast agent, the blood vessels appear very bright, with blockages and plaques that can be identified by a radiologist skilled in reading these images. Performed on an outpatient basis, Coronary CTA takes less than 30 minutes to complete, so a patient can expect to spend about an hour at the imaging center.
Covering the cost of Coronary CTA
Coronary CT angiography is a highly sophisticated test, using leading edge technology, expensive medical equipment, and specialized computer software. We only perform Coronary CT angiography with a doctor's prescription.
To schedule an exam, please contact one of our radiology nurses at 301-896-2704.
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