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Cardiac CT Scan An Alternative To Catheterization

By Michael Lasalandra, Beth Israel Deaconess Medical Center Correspondent

Doctors are now able to image the heart and coronary arteries with a CT scan, avoiding in some cases the need for an invasive test that involves snaking a catheter through the arteries themselves.

Known as cardiac computed tomography angiography (CCTA), the new fast-scan technology provides pictures that are about as accurate as those obtained by catheterization without invading the body. And it can provide information not able to be obtained with catheterization.

"It is an alternative, a complementary imaging modality," says Dr. Diana Litmanovich, Director of Cardiac CT in the Department of Diagnostic Radiology at Beth Israel Deaconess Medical Center. "We can use it to focus on certain patients, and can provide additional information. It is also non-invasive."

Cardiac catheterization, in which a catheter is snaked through the femoral artery into the coronary arteries, shows only the arteries. The test is designed to measure blockage of the arteries.

But with CCTA, "you can see the whole anatomy," she says. "You also see the walls of the arteries and you can categorize the plaque. You can have a much better picture of the anatomy and structure of the disease. You can see how much and what kind of plaque is there."

The test is done along with an electrocardiogram (ECG), a test that measures the heart's electrical activity. "The synchronization of the ECG and the cardiac CT gives us the ability to 'freeze' the heart motion so it does not interfere with the images," she says. The ultra-fast test is particularly useful for patients who have problems holding their breath. The amount of intravenous contrast dye used for this study is equal to a regular chest CT; the major requirement is the need for beta-blocking to reduce the heart rate to below 65 beats per minute.

CCTA is used mostly to image the coronary arteries, but can also look at heart valves and chambers, as well as to assess myocardial function, she notes.

The test is especially useful to assess patients who have moderate risk of coronary artery disease and chest pain. "We want to find out if the pain is due to coronary artery disease or something else," she says. CCTA provides an anatomic image of the coronary arteries and reliably depicts narrowing of the interior of those arteries due to buildup of fat or cholesterol. The idea is to avoid catheterization in cases where there is not a high enough probability to go right to catheterization.

If the test is normal, catheterization is avoided. "We don't want to do catheterization for patients who don't need it," Dr. Litmanovich says.

Another group of patients who may benefit from CCTA are those for whom coronary artery disease is suspected but who are not able to perform a stress test.

Others who may benefit from CCTA include those who have had a previous bypass and are scheduled for another one. The test can evaluate the patient's anatomy in advance of the second surgery. Those with suspected congenital heart anomalies might also benefit from the test.

While the test can diagnose problems such as blocked arteries, it cannot unclog them. In such cases, catheterization might still be needed. In some cases, however, patients might instead try medication to lower cholesterol. After some time on such drugs, the patient can come back again for another CCTA to see if the medication is working.

Initial high radiation exposure reports raised great concerns. The new technology of prospective ECG gating now allows imaging of the coronary arteries at a fraction of the dose levels used in catheter coronary angiography or CT pulmonary angiography, according to Dr. Litmanovich

ECG gating takes an image at a specific time of the cardiac cycle, from one heart beat to the next. Prospective ECG gating delivers a radiation beam intermittently during the scanning process.

This Low Dose Coronary CTA technique is now available at BIDMC on an outpatient, inpatient or emergency basis depending on the indications for the study.

Above content provided by Beth Israel Deaconess Medical Center. For advice about your medical care, consult your doctor.

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