Cardiac catheterization has been the gold standard for detecting the extent of coronary artery disease (CAD) for years. But that paradigm is changing…quickly. Thanks to the jump-start of 16-slice cardiac CT angiography, more recently the huge surge in 64-slice scanner sales and the growing excitement around Dual Source CT systems, multidetector CT is providing a faster, cheaper, and noninvasive method for obtaining much of the same information.
Clinical studies have shown that cardiac CT has 95 to 99 percent accuracy (sensitivity and specificity) when it comes to ruling out coronary artery disease (CAD)—in a single patient breath hold. Similar advantage is seen in detecting peripheral vascular disease (PVD), namely in vertebral and carotid arteries, aneurysms, arch vessel disease, infrapopliteal and calcified vessels, evaluating stents and bypass grafts and in trauma evaluation. And more potential exists in lumen reduction and atherosclerotic plaque identification, characterization and quantification that some day, researchers hope, will help in more effective risk stratification as well as statin dosing and therapy management.
In a field where new advancements come fast and furiously, cardiologists and radiologists—most often working in collaboration—are embracing the techniques even as validation studies are still in the works. And with heart disease as the leading killer of Americans and most developed countries, there’s no time to waste.
“Coronary CTA is stretching the physical boundaries of CT in imaging such small and more rapidly moving anatomy,” says Stephan Achenbach, MD, president of the Society of Cardiovascular CT (SCCT) who spoke at the society’s 1st annual meeting mid-July in Arlington, Va. He is an assistant professor of medicine at the University of Erlangen in Germany and was described at the meeting as the “grandfather of coronary CTA,” albeit at a young age, by other leaders in the field.
Multidetector CT scanning has taken the cardiac imaging arena by storm—based on the fastly surging number of facilities offering CCTA scanning and physicians being trained in the evaluation of images. That the current multidetector CT scanner has sufficient spatial and temporal resolution to image the coronary arteries means physicians can detect the presence, extent and location of coronary calcifications. Note that the cath lab maintains the advantage in spatial and temporal resolution, offering spatial resolution of 0.2 mm vs. 0.4mm in CCTA, and temporal resolution of 8 milliseconds vs. 80 to 200 ms for CCTA. It’s also important to note that right now there is a tendency for CCTA to overestimate stenosis slightly when compared with cath lab findings.
Yet, CCTA’s recent technological advances mean high resolution, three-dimensional images that may soon replace cardiac catheterization in many cases. In other cases, cardiac CTA may help lock in the decision that it’s best to send a patient to the cath lab for stenosis repair or directly to surgery when cardiac bypass is essential. Achenbach urges physicians to ask the scanner: “Is this a patient who does NOT need a cardiac cath?” If the CT is normal, he sees no reason for further workup.
When Baylor Heart and Vascular Hospital in Dallas opened in 2002, leadership decided to go with a 16-slice CT scanner rather than focusing on MRI. The cardiologists at the 50-bed facility had to bet on what would be the next big technological advance in cardiac imaging. “It was a huge gamble,” said Jeffrey Schussler, MD. “CT looked very promising but we didn’t realize it was going to be as big as it has become.” They did hedge their bets—if heart CT evaluation didn’t work out, the facility could still use the scanner for peripheral angiography.
But, the scanner “really does what it says it’s going to do,” Schussler says, “which is look at heart arteries without being inside them. The fundamental question is: Is there a blockage that needs to be fixed? A CT scan can answer that question very well.”
The facility was so pleased with its 16-slice scanner that it added a 64-slice CT scanner from GE Healthcare to its arsenal a year and a half ago.
A new standard of care
64-slice CT scanning is the new standard of care for cardiac imaging because it offers an accurate, noninvasive image for about one-sixth of the cost of a cardiac catheterization, let alone the patient care benefits.
“We spend over $10 billion a year [in the U.S.] on cardiac catheterization,” says Claudio Smuclovisky,