Winter 2008

CTA Provides Noninvasive Coronary Screening

A unique combination of technology and expertise is now allowing physicians in UCSF's Heart and Vascular Center to more effectively screen patients for coronary artery disease, thereby helping many patients avoid undergoing cardiac catheterization.

The technology is coronary computed tomographic angiography (CTA), a five-second imaging test that produces highly accurate, 3-D images of the heart and blood vessels. These images, in turn, allow for early detection of coronary artery disease (CAD), the leading cause of morbidity and mortality in the United States and other industrialized countries.

The technology is especially good at screening patients with low to moderate levels of risk for heart disease, such as those who have typical or atypical heart pain, but normal EKGs and normal serum levels of cardiac enzymes. Other good candidates include those who are asymptomatic, but have multiple coronary risk factors (such as smoking, male sex, age over 40 years, elevated serum cholesterol and family history of CAD) and patients who arrive at the ER with signs that are inconclusive or unclear.

UCSF staff members have been doing research with CT scans since 1995, longer than any other institution in the country, and UCSF has one of the few heart centers in the country with a 64-detector scanner. This affords specialists in cardiology, surgery and radiology at the Heart and Vascular Center extensive experience with the technology in both research and clinical care.

"We can offer expertise in both CT imaging and cardiac imaging," says Gautham P. Reddy, M.D., M.P.H., who is chief of cardiac and pulmonary imaging at the UCSF Heart and Vascular Center. Indeed, the center's Charles Higgins, M.D., professor of radiology, is widely considered to be the foremost international expert on noninvasive cardiac imaging for both children and adults.

UCSF's CT scanner is one of the most sophisticated models ever built, as it features detectors that help create 64 images, or "slices," of the heart instead of the standard 16. These slices are then compiled via computer into 3-D images of the heart and blood vessels. As such, the images created by the 64-slice CT scan are far clearer and contain far more detail than a traditional CT scan, and can show both stenotic areas of the blood vessels and early disease in the vessel walls. Between 80 percent and 90 percent of the scans that show coronary stenosis or occlusion are accurate.

Equally important, the CT scan allows for highly accurate detection of a lack of coronary artery disease. Currently, 40 percent of all patients who undergo catheterization have no heart disease. With the 64-slice CT scan, however, "if the image shows no heart disease, it's very likely there is no heart disease," Reddy says. That means more patients can avoid undergoing the more invasive catheterization. "This is really the group we're looking for: the patients who have no disease," Reddy notes. "We don't want to send them on to an invasive procedure if they don't need it."

Unlike catheterization, CTA is relatively quick and noninvasive. The entire office visit takes about 90 minutes from start to finish, which includes giving the patient time to undress, putting in an IV, administering medications (including sublingual nitroglycerine and beta blockers), taking a chest EKG, injecting the iodine-containing contrast dye and monitoring the patient after the procedure.

"Our scanner is set up in the ER," Reddy says, "which allows us to triage the patients more effectively. If we see abnormalities on the scan, we immediately send them on to catheterization. If we see no evidence of coronary artery disease, we can look at other causes."

CTA is also effective in assessing bypass grafts for narrowing or obstruction, detecting congenital coronary artery anomalies in young patients presenting with chest pain, and checking for left ventricular function and volume.

In about 25 percent of the scans, physicians find other types of abnormalities, including cardiac tumors, lung cancer, pulmonary embolisms or ventricular aneurysms. "In most cases, these were unsuspected abnormalities," Reddy notes.

The 64-slice CT scan isn't appropriate for all patients, however. Patients with hardened plaque, for instance, are not good candidates for the screening because the calcium spots create a blooming effect on the images, which can make the disease look worse than it is. Similarly, patients with coronary stents are not good candidates for the technology, as the stents tend to degrade the image quality. The screening is safe for patients with pacemakers, although the pacemaker leads, too, can degrade the image quality.

To contact Dr. Gautham Reddy, call (415) 476-3849.

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