At the invitation of prestigious Weill Cornell Medical College in New York, Oconee Heart and Vascular Center cardiologist Erick Avelar, M.D., will be the lead local researcher in a clinical trial funded by the National Institutes of Health to study the ability of Computed Tomography – CT – to measure disease in the heart’s arteries.

The CREDENCE trial, which stands for Computed TomogRaphic Evaluation of Atherosclerotic DEtermiNants of Myocardial IsChEmia, will include 20 facilities worldwide and will enroll 618 patients as test subjects. The goal of the study is to find out if non-invasive cardiac CT is as effective as invasive cardiac catheterization in measuring how much an artery-narrowing plaque decreases blood flow.

Dr. Avelar was invited due to his success in enrolling patient volunteers in a previous NIH-funded study called PROMISE, which enrolled 10,000 patients to determine if CT is an effective way to find coronary artery blockages.

“The CREDENCE trial takes the PROMISE study one step further,” Dr. Avelar said. “We know CT can detect blockages, perhaps with better sensitivity than a conventional stress test. Now we are trying to find out if CT is an accurate way to measure how significant those blockages are. Ultimately, we want to determine the safest, most cost-effective way to diagnose coronary artery disease.”

Coronary artery disease is the leading cause of death in the United States. According to the CDC, about 600,000 Americans die each year from coronary artery disease – more than all forms of cancer combined – generating costs of nearly $109 billion. Patients with coronary artery disease experience a range of symptoms from mild angina during exertion to heart attack, with women often experiencing subtler symptoms than are typical in men.

Dr. Avelar, who is an associate professor of medicine at the GRU/UGA Medical Partnership and the only Harvard-trained cardiac imaging reader in the Athens area, explains coronary artery disease this way: Cholesterol, inflammatory cells and, eventually, calcium build up inside an artery wall. This build-up forms a plaque that narrows the artery and can restrict blood flow. With less blood flow, heart tissue becomes stressed, resulting in chest pain that gets worse as the disease progresses. Over time, the plaque can cause a heart attack by rupturing or growing so large it completely obstructs the artery.

“It is very important to know how much a lesion in a coronary artery is impacting blood flow,” Dr. Avelar said. “It is already known that CT can detect coronary lesions. Now we’re trying to determine if CT is as effective as invasive coronary angiography at measuring the significance of those lesions.”

Currently, invasive coronary angiography with Fractional Flow Reserve is the only way to measure the significance of a coronary lesion. In ICA, which is a type of cardiac catheterization procedure, the cardiologist makes a puncture in an artery in the groin or wrist and inserts a thin, flexible tube called a catheter into the blood vessel. Using x-rays and contrast for guidance, the cardiologist steers the catheter into the narrowed blood vessel in the heart and physically measures pressure inside the artery above and below the lesion.

In comparison, CT uses only x-rays, contrast, and a workstation with the ability to create 3D images of the diseased artery.

“The advantages will be tremendous if CT is found to be as effective as ICA at measuring fractional flow reserve,” Dr. Avelar said. “CT poses much less risk of external bleeding, hematoma or infection, and no risk of internal artery damage. An ICA takes about 45 minutes. Using CT, we can now image an artery in about five minutes. In addition, CT requires no sedation or recovery time, is virtually painless, and is less expensive. Those are significant advantages, but first we have to find out if CT is as good as ICA at assessing the significance of a coronary lesion. If it is, then we will be better able to determine which patients need an invasive procedure and which do not.”

Patients who volunteer for the CREDENCE trial and who meet criteria will each receive three diagnostic tests at St. Mary’s: a traditional stress test using either nuclear medicine or MRI, CT angiography using the hospital’s high-speed Toshiba 64-slice CT scanner, and an ICA in St. Mary’s Cardiac Catheterization Laboratory. CREDENCE will pay any costs not covered by the patient’s insurance. The University of Georgia will provide local institutional oversight to ensure testing complies with the highest standards for validity and patient safety.

The CREDENCE trial also will be taking a preliminary look at how well CT reveals the composition of plaques, Dr. Avelar noted. The hope is that CT can help doctors determine which plaques are most likely to obstruct blood flow and possibly cause a heart attack.

Local recruitment of participants is now underway following formal Institutional Review Board approval. Enrollment is expected to take one to two years, after which researchers will analyze data from all study sites. Results will be reported at a national cardiology conference.