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Cardiovascular Report - The Newest CT: Faster Than a Heartbeat
Cardiovascular Report Summer 2014
The Newest CT: Faster Than a Heartbeat
Date: June 13, 2014
New CT scanner may replace invasive tests.
Joao Lima sees CT as the ultimate device for assessing patients for CAD the world over.
photo by Keith Weller
In one revolution around the body, the newly arrived 320-detector computed tomography (CT) scanner at The Johns Hopkins Hospital is poised to change the management and outcomes of coronary artery disease (CAD).
The only other such scanner in the U.S. is at the National Institutes of Health, which is where Joao Lima, director of cardiovascular imaging for Johns Hopkins, and his colleagues collaborated in adding new features and validating its use for detecting anatomic and functional characteristics of CAD. Johns Hopkins will be the first to use the new scanner for clinical purposes.
The fastest CT scanner available, with a 0.275 gantry rotation, it scans cardiac vessels and the heart in less time than it takes for a single heartbeat. It captures the heart midcontraction, freezes the motion and significantly reduces artifact, even in patients with a rapid heart rate. Where with earlier generation CTs, patients with a heart rate higher than 70 beats per minute were treated with a beta-blocker to slow the heart and reduce image artifact, the new system eliminates that need. The speed translates into better cardiac imaging, improved temporal resolution, and lower amounts of contrast medium and radiation exposure needed to acquire the best images and data.
The scanner is also poised to replace invasive tests (e.g., angiography, nuclear medicine stress test) for sorting patients having chest pain who need intervention (e.g., coronary angioplasty, a cardiac stent, bypass surgery) from those who don’t. About 30 percent of patients receiving these invasive tests turn out to need no intervention at all. The new CT short-circuits this usual path to diagnosis and treatment.
Lima and his colleagues showed in an international, prospective study of 381 patients that two tests they developed for the 320 scanner are as good as or better than conventional tests at revealing the anatomy and perfusion of the coronary vessels. The first test is called computed tomography angiography (CTA); the second, computed tomography perfusion (CTP). With CTA and CTP, the doctors can visualize the integrity of the vessels and assess whether blockages prevent perfusion of the heart muscle.
“Our goal is to increase certainty about which patients need an invasive procedure for opening an arterial blockage and to spare patients who do not from unnecessary diagnostic procedures,” says Lima. “The CTP test developed by Johns Hopkins cardiologist Richard George makes it that much more obvious.”
Lima and colleagues plan to study how features related to arteriosclerosis, calcification, stenosis, perfusion defects and cardiac muscle flaws affect clinical outcomes. They hope to identify patient subgroups for whom specific strategies and treatments will be most advantageous.
“Speed and diagnostic accuracy are the bottom line,” says Lima. “We are learning more and more, which clinicians everywhere can use to make better assessments of coronary disease and administer the best care.”