ATLANTA — Immediate 64-slice CT angiography in patients with low-risk acute chest pain definitively excludes significant coronary artery disease faster—and at less cost—than the standard emergency department work-up, Dr. Gilbert L. Raff said at the annual meeting of the American College of Cardiology.
He presented the results of a 200-patient randomized controlled feasibility study conducted at the William Beaumont Hospital in Royal Oak, Mich. Its positive findings have served as impetus for a more definitive 500-patient multicenter randomized trial now being organized under the auspices of the recently formed Society of Cardiovascular Computed Tomography.
In the feasibility study, 200 patients who presented to the emergency department (ED) with what was deemed by physicians to be low-risk chest pain were randomized to immediate CT angiography or the rule-out evaluation that is standard in many U.S. EDs. This includes serial cardiac enzyme measurements, ECGs, and sestamibi stress nuclear blood flow imaging.
Median time from ED admission to discharge was 12.5 hours in the CT group and 22.1 hours in patients who underwent the standard rule-out work-up. And the $1,586 median cost of care in the CT group was nearly $300 less than in controls. Both of these differences were statistically significant, said Dr. Raff, medical director of the cardiac CT/MRI department at William Beaumont.
CT angiography previously has been shown to have roughly a 95% negative predictive value for significant coronary artery disease (CAD). “There's no other noninvasive test that even comes close,” the physician asserted. Dr. Raff characterized the standard rule-out evaluation for acute chest pain as “very compulsive, tedious, lengthy, time consuming, and expensive.”
“There is zero tolerance for missed coronary chest pain in the emergency medicine world. Consequently, the kind of experience patients have is quite different from what they expect. When they come to the emergency room with chest pain they would like to have an answer quickly and go home—and they don't,” Dr. Raff explained.
To harness the strengths of CT angiography—its speed and unparalleled negative predictive value—he and his colleagues devised a study protocol in which patients deemed not to have clinically significant CAD—meaning no luminal stenoses of 25% or greater on CT—were immediately discharged.
Those with a stenosis in excess of 70% were admitted for cardiac catheterization. And just to be safe, those with an intermediate 25%–70% stenosis also underwent stress nuclear imaging, the results of which determined whether a patient would be discharged or referred for catheterization.
CT angiography alone excluded significant CAD in 67% of patients. Another 8% were sent directly to the catheterization laboratory on the basis of their CT findings. So only one-quarter of patients in the CT study arm had to undergo a nuclear imaging study. No cardiovascular events occurred during 90 days of follow-up in patients discharged after being found not to have significant CAD.
An intriguing finding was that 9 of 12 patients who underwent cardiac catheterization on the basis of their CT findings proved to have clinically significant CAD, compared with 1 of 5 in whom the standard evaluation led to angiography.
This finding raises a key question: Does the standard rule-out work-up miss significant CAD, or does CT angiography overcall it? Investigators hope that the planned large multicenter trial will provide the answer.
It has been estimated that 2%–4% of patients discharged from EDs after being told their chest pain is not of cardiac origin actually have an MI, which is why missed MI is the No. 1 cause of malpractice litigation in emergency medicine.
Until now, CT angiography has been reserved for chest-pain patients categorized as intermediate risk, but the William Beaumont study challenges that.
“If you consult the people doing research in the field, the overwhelming feeling is that because of the extremely high sensitivity and relatively low cost, CT is most appropriate in low-risk patients. A lot of patients who present with chest pain and an atypical story would have a false-positive stress test; in those cases a CT scan might be the first study to do—if further research confirms that,” Dr. Raff said.
More than 5 million Americans each year present to emergency departments with acute chest pain. The vast majority of these patients do not have significant CAD, and the estimated cost of their diagnostic work-up exceeds $12 billion.
Arrows indicate locations of severe stenoses in the left anterior descending artery and right coronary artery. Courtesy Dr. Gilbert l. Raff