CT scans could "change the paradigm" for heart disease

Posted on Nov 22, 2010 in Uncategorized

November 18, 2010

by Brendon Nafziger, Writer

SPECT nuclear medicine scans have long been the gold standard for gauging the sluggish blood flow indicating heart disease. And angiograms are the standard tool for discovering blocked arteries.

But now a group of Johns Hopkins University doctors suggest a combination of two ultra-high-slice CT scans can produce results nearly as accurate as both tests, with a mite less radiation and in less time.

In a study presented earlier this week at the American Heart Association’s annual meeting in Chicago, scientists said two scans using a high-powered 320-slice CT scanner identified most of the patients picked out as having heart disease by SPECT imaging and angiograms.

“This shows the kind of results that could really change the paradigm for diagnosing coronary artery disease,” lead researcher Dr. Richard George, a cardiologist and assistant professor of medicine with Johns Hopkins, told DOTmed News.

The researchers hope the combined CT scans could help make treatment planning simpler for the many Americans who suffer from coronary artery disease, or CAD. Every year, around 800,000 Americans suffer a heart attack due to CAD, with 150,000 of them dying, according to Johns Hopkins.

For the study, the researchers examined 50 patients who came to Johns Hopkins Hospital in Baltimore complaining of chest pain. All patients got a SPECT scan. Nineteen of the patients, those suspected of having hardening arteries, also received an angiogram, a somewhat invasive test which involves threading a catheter up blood vessels.

In addition to the traditional heart disease tests, the patients received two CT scans with the Aquilion One, an advanced CT scanner made by Toshiba America Medical Systems of Tustin, Calif., which also helped fund the study.

The two scans were a CT angiogram, or CTA, to gauge arterial plaque build-up, and a CT perfusion test, or CTP, to measure blood flow. For CTP scans, doctors have to inject iodine to make blood flow visible, and they also have to inject adenosine to cause the heart to pump faster.

How did the modalities stack up? CTA plus CTP had 71 percent sensitivity in identifying patients with reduced blood flow. The CT scans were also able to rule out 90 percent of the patients who did not have blood flow problems.

The CT scan combination also had 90 percent accuracy in detecting patients with clogged arteries, with 89 percent specificity. (For specific blood vessels, CTA and CTP were 75 percent as sensitive as the other tests, and 91 percent as specific.)

“You can never be better than your gold standard,” George said. “No matter what you compare anything to, it’s always going to be below it. But those accuracies are as good or better than any test that has been compared to a gold standard. So they’re very good.”

And while perhaps not as accurate as SPECT scans and angiograms, the CT scans were more efficient. The two scans took about half an hour, compared with the two hours it takes for patients to absorb an injected chemical tracer for SPECT scans. Plus, patients only needed one appointment for diagnostic information ordinarily provided by the two separate tests.

The CT scans also involved less radiation, around 11.5 mSv for the two CT scans, versus an average of 13 mSv for the SPECT scans. They also don’t involve the quite low but still real risks of serious adverse events — around three in 1,000, George said — from angiograms.

The 2-metric-ton Aquilion One, which Johns Hopkins was among the first to install three years ago, isn’t available everywhere. But George said earlier tests were done on less powerful equipment.

“We think there are advantages to having a 320, but this technique can be done on scanners with 64 and 128 detectors,” he said.

A Toshiba spokeswoman told DOTmed News around 245 of the 320-slice CT scanners have been shipped worldwide.

But the researchers cautioned that it’s too early to decide the clinical value of the tests until a larger study wraps up. In January, the researchers started the CORE 320 study. George said they’re still enrolling patients, and hope to have around 400 by the time it finishes over the next year or so.

“We feel confident that the study shows great promise,” he said.