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Nov. 5 - High-tech CT Scans: Not a Bad Choice to Test for Clogged Arteries

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 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 as much as 25% 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% of patients with blockages were detected by 64-CT and that the scans were able to diagnose 83% 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% of the time with results from invasive catheterization in detecting patients with blockages.

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

The new study also suggests that the new scanners, four times quicker than the more widely used 16-CT, may be a good alternative to cardiac stress testing, which evaluates heart function by measuring the effects of hard exercising. Exercise stress testing generally cannot safely be performed on the weak and elderly.

The CT scanner used in the study was an Aquilion 64 CFX multislice CT scanner, manufactured by Toshiba. Similar devices also are manufactured by Siemens and General Electric. Each machine costs between $1.5 million and $2 million. A single test costs approximately $700.

Source: Johns Hopkins Medicine

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