Coronary CT Angiography for Acute Chest Pain

Published - Written by Daniela Lamas

Anyone who’s worked in the Emergency Department knows the drill.

A 50-year old hypertensive woman comes in with three days of intermittent, pressure-like chest pain. It’s worse when she exercises, but also when she lies down after a meal. Her EKG has no changes to suggest ischemia, and her initial troponin is negative. But is that enough to discharge her home from the ED? “Let’s just rule her out,” the attending says. So she’s admitted to the hospital.

Chest pain is the second most common reason for ED visits nationwide, with more than 6 million people each year presenting with this complaint. While only about 10 percent are ultimately diagnosed with an acute coronary syndrome, the majority of patients are admitted. The inefficiency and frustration inherent in this system, both for physician and patient, have led investigators to examine other tests that can better risk stratify who can be discharged, and who needs to stay in the hospital.

To that end, coronary CT angiography (CCTA), has been shown to have a strong negative predictive value in a population with a-low-to-intermediate risk of coronary artery disease. However, the concern remains that, when applied to a real-world population, the CCTA strategy might actually lead to more procedures down the line, at a greater cost. When it comes to actually incorporating CCTA into the emergency department protocol for chest pain, the jury’s still out.

In this week’s issue of NEJM, Udo Hoffmann and colleagues report on  their major comparative-effectiveness study of CCTA versus standard diagnostic workup. They conclude that the length of stay is shorter with CCTA; however, this approach leads to an increase in downstream testing and radiation exposure, with no change in cost overall.

In their study, patients age 40 to 74 who presented to the ED with chest pain –without ischemic EKG changes or positive cardiac enzymes – were randomized to either standard workup or CCTA. Patients were only enrolled on weekdays, during daylight hours. Those with known coronary artery disease were excluded.

The investigators ultimately enrolled 1,000 patients; half were randomly assigned to CCTA , half received standard evaluation in the ED. Among those assigned to the imaging study, hospital length of stay was 7.6 hours shorter, and almost half were discharged straight from the ED (in contrast to 12% in the standard evaluation group). Ultimately, 75 patients (8%) were diagnosed with an acute coronary syndrome. Importantly, there were no known episodes of ACS that went undetected in either group, and cardiovascular outcomes at 28 days were equivalent.

So if patients can be discharged quicker, is CCTA the way to go? The problem is that those earlier discharges come with some tradeoffs. Notably, those who were assigned to a CT scan had higher rates of coronary angiography, and were more likely to undergo revascularization. And, they received nearly triple the amount of radiation.  Despite the decreased hospital stay, cost in the CCTA group was slightly higher.

In an accompanying editorial, Dr. Rita Redberg from the University of California, San Francisco writes that – perhaps – we’re really asking the wrong question. The assumption behind studies of CCTA is that we need a way to further test patients at low-to-intermediate probability of a coronary event before we can safely discharge them. But, as Hoffmann’s study demonstrates, no test comes without risk.

Thus, Redberg suggests, perhaps our question should be whether these tests are even necessary — or are causing more harm than good. “In short, the question is not which test leads to faster discharge of patients from the emergency department, but whether a test is needed at all,” Redberg writes. “The Choosing Wisely campaign reminds physicians to order testing only when the benefits will exceed the risks. I believe judicious clinical follow-up is safer and in the best interests of the majority of these patients.”