New views of heart disease
The coming revolution in cardiac imaging
Advances in imaging techniques over the past five years have vastly improved the ability to diagnose and treat cardiac disease, but that’s just the beginning.
Constantly improving technologies are on the brink of revolutionizing the way that medicine approaches cardiovascular illness by allowing safer and less invasive methods for current procedures and permitting the detection of pre-clinical disease.
Cardiac catheterization (also known as angiography) has been widely used for more than 30 years to diagnose coronary artery disease. A thin tube, or catheter, is inserted into an artery and is guided to the coronary arteries using X-ray fluoroscopy. A contrast agent injected through the catheter outlines the arteries in X-rays.
The evolution of computed tomography (CT) scanners has increased the speed, spatial resolution and the clarity of the scans, and eliminated the need to insert catheters.
“Coronary CT angiography (CTA) is diminishing the need for arterial catheterizations for a purely diagnostic use, although catheterization is still the mainstay for interventional treatment,” says Murray Mazer, M.D., a cardiovascular radiologist at Vanderbilt University Medical Center.
“Coronary CTA at present is the only non-invasive method with potential to do a good job imaging coronary arteries,” he says. It may be especially important for determining the source of chest pain in the emergency room in a more efficient manner than is done today.
CTA is fast (results within 1 hour) and is 99 percent accurate in determining the absence of significant coronary artery disease. Using CTA in the ER would allow simultaneous evaluation of the pulmonary arteries, while ruling out incidental findings such as lung tumor or perforated esophagus, which also can cause chest pain.
At the same time, says Mazer, “careful control of imaging techniques and X-ray dose modulation software have diminished X-ray dosages by 50 percent to70 percent, allowing this technique to compare favorably with other cardiac imaging modalities.”
Magnetic resonance (MR) is another flourishing imaging modality.
Mark Lawson, M.D., an assistant professor of Medicine and Radiology, heads up Vanderbilt’s relatively new cardiovascular MR suite. Using a dedicated cardiology magnet to look for artery blockages, Lawson and his colleagues can perform a heart and whole body angiogram in 45 minutes.
“The image quality for most angiograms is comparable to CT,” says Lawson. Because MRI is non-invasive and doesn’t require the use of X-rays, patients can have several scans over time to track the progress of their disease.
As stronger magnets are developed, MR will achieve better spatial and temporal resolution, he predicts. Combined with the rapid development of new contrast agents, these advances may lead to the development of coronary MR angiograms, and provide an alternative to CT angiography.
MR technology has several other applications to cardiovascular medicine as well—monitoring bone-marrow derived stem cells used in cardiac regenerative therapy is one example.
At Vanderbilt, for example, Darryl J. Bornhop, Ph.D., and his colleagues in the Department of Chemistry are developing “contrast agents” that could bind to the transplanted stem cells to track their health and survival.
MR eventually may be used to screen high-risk patients for pre-symptomatic signs of cardiovascular disease.
“Once there’s a blockage, the horse is out of the barn,” says Lawson. With the improved spatial resolution of stronger magnets, “we could see atherosclerotic changes in the wall of the artery before blockage forms.”
View Related Article:
“Big science” in the balance