Cardiac CT offers physicians strong predictions of major adverse cardiac events (MACE) in ED patients presenting with chest pain, supplementing clinical risk scores and offering a two-year MACE-free warranty period in the absence of coronary artery disease (CAD), according to the two-year outcomes of the ROMICAT study published in the May issue of the Journal of the American College of Cardiology.
A number of studies have examined the prognostic value of CT among patients with CAD, though most have either utilized retrospective designs or omitted ED patients, reported Christopher L. Schlett, MD, from the department of radiology at Massachusetts General Hospital, Harvard Medical School, in Boston, and co-authors.
Schlett and colleagues investigated the prognostic utility of CT to triage patients presenting to the ED with acute chest pain. The authors followed patients enrolled in the single-institution ROMICAT (Rule Out Myocardial Infarction Using Computer Assisted Tomography) trial for a median of 23 months, with complete information available on 333 of 368 participants.
All patients presented to the ED with the chief symptom of acute chest pain and normal initial troponin levels and ECG findings. Patients underwent 64-slice CT angiography, which was evaluated for its prognosis regarding MACE endpoints of cardiac death, ST-segment elevation myocardial infarction (STEMI), non-ST-segment elevation myocardial infarction (NSTEMI) or coronary revascularization.
Just under 7 percent of patients experienced a total of 35 MACE—12 myocardial infarctions and 23 coronary revascularizations. No cardiac deaths were observed in follow-up, which consisted primarily of telephone interviews with patients.
Patients without CAD had a 0 percent likelihood of experiencing a MACE, whereas patients with nonobstructive CAD had a 4.6 percent chance of MACE. Among participants with obstructive CAD, the likelihood of MACE increased to 30 percent.
MACE were likewise observed in 30 percent of patients with stenosis, a 20-fold increase in risk compared with the 2 percent of stenosis-free patients who experienced MACE. After adjusting for cardiac medications, stenosis on CT still resulted in a 16- to 21-fold increase in patients’ risks of MACE.
When functional analysis was added to CT findings, patients without stenosis or right wall motion abnormalities had a 1 percent chance of MACE, compared with a 10 percent risk for patients with stenosis only and a 15 percent risk for patients with right wall motion abnormalities only. The probability of MACE jumped to 62 percent in patients who experienced both stenosis and right wall motion abnormalities.
“Importantly, in our patients without CAD on CT, the cumulative 2-year probability for MACE was 0 percent, which provides support for at least a 2-year MACE-free warranty period in patients with normal CT findings in the ED patient cohort,” Schlett and colleagues argued.
“This represents 50 percent of our ED patients with acute chest pain, initial negative troponin, normal or inconclusive findings on electrocardiography, and low to intermediate risk of acute coronary syndrome and provides further reassurance to ED physicians that early triage using cardiac CT would be a safe strategy,” the authors continued.
“Several important issues merit mention,” cautioned an editorial written by Paul Schoenhagen, MD, from the Imaging Institute at Cleveland Clinic in Ohio, and colleagues. Schoenhagen and co-authors first pointed out that the study did not differentiate between revascularization performed before coronary CT angiography vs. 60 to 90 days post-imaging. The latter, Schoenhangen and colleagues argued, is more critical and an entirely different phenomenon.
“As another relevant issue,” the editorial continued, “the study cohort had an overall hard event rate (cardiac death and myocardial infarction) of 1.9 percent per year and therefore constituted a relatively low-risk group (12 myocardial infarctions in 333 patients over 23 months). Hence, 333 patients were tested to identify 183 at low risk (no obstructive CAD) and 25 who went on to have events, most of which were revascularizations, a relatively poor yield.”
Schlett and colleagues conceded that a multi-institution study would be necessary to validate their findings. “We urgently need large-scale trials so that clinical guidelines based on comparative effectiveness data, rather than expert consensus alone, will direct individual patients