Features March 2017 Issue

Study: Cardiac CT Reduces Need for Angiography in Some Patients

In some cases, non-invasive computed tomography (CT) scanning can help diagnose or rule out heart disease in people with atypical symptoms.

Coronary artery disease (CAD) can be diagnosed in several ways. For some people, a heart attack is their first clue that the arteries in the heart are blocked. For many others, however, symptoms such as chest pain prompt an evaluation of the heart, which leads to the discovery of CAD.

cardiac ct scan

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Cardiac CT scans use layers of special x-ray images to create 3-D views of the heart.

One of the most well-established and accurate diagnostic tools is coronary angiography. In this procedure, a thin, flexible catheter is threaded through a blood vessel and into your heart. There it releases a dye into your coronary arteries. Special x-rays are used to show how the dye moves through your arteries. A computer uses the x-rays to create a 3-D image of the heart. This imaging tool can show whether there is blockage in one or more arteries.

New research, however, suggests that many patients may not need this invasive procedure. A study published in The BMJ found that an imaging procedure called cardiac computed tomography (CT) can significantly reduce the need for coronary angiography.

The small study, which involved 340 patients, found that the need for coronary angiography went from 100 percent to 14 percent when comparing cardiac CT with direct coronary angiography. Christine Jellis, MD, PhD, a heart imaging specialist at Cleveland Clinic, says those findings aren’t a surprise since the study participants were considered to be only at intermediate risk of CAD. She also noted that the small size of the study somewhat limits the conclusions that can be drawn from its results.

“Reassuringly, major procedural complications were actually low for both groups, and unsurprisingly minor complications were higher in the angiography group,” Dr. Jellis says. “I don’t think it will really change our current clinical practice that much, although the reduction in length of stay with CT is important in this day and age of cost repositioning when we are trying to minimize more costly admissions.”

The intermediate-risk patients in the study had suspected CAD based on atypical chest pain. Atypical angina (CAD-related chest pain) is unpredictable, may last a few seconds or all day, and may feel sharp or pulsating. Typical angina usually lasts three to 15 minutes, is fairly predictable, tends to radiate out to the neck, jaw or shoulders, and feels like there is pressure on the heart or that it is being squeezed.

When to Use Angiography

While minor procedural complications were somewhat higher with coronary angiography, the procedure still has an important place in diagnosing CAD. “Angiography is usually better for higher-risk patients and those with previous stents or bypass grafts,” Dr. Jellis says.

She adds that coronary angiography has an advantage over cardiac CT, because those scans can sometimes include artifacts, which are imaging errors that don’t accurately reflect the blood vessels being scanned. Calcified coronary arteries are especially likely to cause artifacts to appear.

Along with administering dye, the catheter procedure can also sometimes address problems with stents in the coronary arteries and provide information about pressures inside the heart if required. Cardiac CT scans can’t do either of these things.

How is Cardiac CT Best Used?

Cardiac CT is often the best choice when there is a low probability that CAD exists. It’s also readily available, non-invasive, painless and requires no overnight hospital stay. Coronary angiography can sometimes mean a stay in the hospital while you recover.

“CT is generally best for its negative predictive value,” Dr. Jellis says. “Patients who are relatively low or intermediate risk may then have a negative study and be reassured with high likelihood that they do not have coronary artery disease. It is not as useful in high-risk patients who will likely need a catheterization anyway, resulting in their having two exposures to radiation.”

Know the Risks

Radiation exposure is a risk for both procedures, though new technology is reducing that exposure. But cardiac CT and coronary angiography each have other risks, too. With CT, for example, you may need a medication to slow down your heart rate and widen the arteries to allow for better image quality, Dr. Jellis says.

With angiography, some people can have a bad reaction to the contrast dye that is used. Also, because it is an invasive procedure, there is a risk of infection or other complications. Though rare, a heart attack or stroke is possible as a result of an angiography or any heart procedure.

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