A study by an international team of cardiac imaging specialists, led by researchers at Johns Hopkins, concludes that sophisticated computed tomography (CT) scans of the heart and its surrounding arteries are almost as reliable and accurate as more invasive procedures to check for
blockages.

Researchers say the newer, 64-slice CT scans, first introduced in the United States in 2005 and initially tested at Johns Hopkins, won't replace the need for inspecting arteries by cardiac catheterization, also known as coronary angiography, but the scans will help cardiologists more quickly rule out those who can skip the more invasive procedures. Studies suggest that as much as 25 percent of the 1.3 million cardiac catheterizations performed each year in the United States may be unnecessary.


The latest study also showed that early detection with 64-CT is a good predictor of who will need angioplasty or coronary bypass surgery to open up new blood supply routes to the heart.

Results showed that on average 91 percent of patients with blockages were detected by 64-CT and that the scans were able to diagnose 83 percent of patients without blockages. This reliability, researchers say, allows them to accurately identify patients who need angioplasty or bypass surgery. More than a quarter million Americans undergo coronary bypass surgery each year.

In the study, investigators selected 291 men and women over the age of 40 who were already scheduled to have cardiac catheterization to check for blocked arteries. Each underwent a 64-CT scan prior to catheterization. Participants were then monitored through regular check-ups to identify who developed or did not develop coronary artery disease and who required subsequent bypass surgery or did not need surgery.

After the first year of monitoring, to continue annually until 2009, researchers found that results from 64-CT scans matched up 90 percent of the time with results from invasive catheterization in detecting patients with blockages.

In other measures, researchers found that 64-CT scans were 83 percent to 90 percent accurate, while tests using older, 16-CT scans were in some instances only 20 percent to 30 percent as precise.

"This study is the first step to realizing the full potential of CT imaging in predicting coronary artery disease, and these scans complement the arsenal of diagnostic tests available to physicians to prevent heart attacks," says cardiologist Julie Miller, M.D., who led the study at Johns Hopkins.

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