Chicago, IL—In patients at low to intermediate risk of coronary artery disease (CAD) presenting with chest pain, a rule-out strategy using primary coronary computed tomographic angiography (CTA) versus traditional care was found to be safe and effective to determine patients who could be discharged directly from the emergency department, according to lead investigator Harold I. Litt, MD, PhD, Chief of Cardiovascular Imaging, Department of Radiology, the Perelman School of Medicine, University of Pennsylvania, Philadelphia. Dr Litt presented the results of the multicenter randomized controlled ACRIN (American College of Radiology Imaging Network) PA 4005 study in a late-breaking session at the 2012 American College of Cardiology meeting.
No myocardial infarctions (MIs) or cardiac deaths had occurred at 30 days in 89% of patients who had a negative CTA examination (<50% stenosis), which was the primary end point. ACRIN PA 4005 was sufficiently powered to demonstrate an acceptable primary safety end point of <1% for 30-day major adverse cardiovascular events. These results supported the findings from previous studies, indicating that CTA may be beneficial, in observational or randomized studies, which were too small to conclusively prove safety. Coronary Computed Tomography for Systematic Triage of Acute Chest Pain Patients to Treatment (CT-STAT), a multicenter, randomized study showed that CTA compared with single-photon emission computed tomography myocardial perfusion imaging (SPECT MPI) reduced time to diagnosis and costs, but its numerical reduction in events was not significant.
Chest Pain
This study addressed a large public health issue. Chest pain is the second most common reason for an emergency department visit, leading to 6 million to 10 million annual visits. Although up to 85% of patients ultimately do not have a cardiac cause for their chest pain, most are admitted to the hospital for an evaluation, at a cost of several billions of dollars annually. “This represents a tremendous cost to society and an inefficient use of resources,” said Dr Litt, as well as contributing to overcrowding of emergency departments. “A technique that can efficiently triage these patients into those who can be discharged quickly and the ones who need further evaluation is very important,” to reduce the currently substantial miss rate of 2% to 3% of patients who are discharged with an unrecognized heart attack.
In the CTA arm, 50% of patients were discharged directly from the emergency department compared with 26% of patients receiving traditional care. Length of stay was reduced by 50% in the overall CTA group and by 50% in the patients who had a negative CTA.
ACRIN PA 4005 randomized patients (aged ≥30 years) who had signs and symptoms of acute coronary syndromes and a thrombolysis in MI risk score of 0 to 2 in a 2:1 fashion to either CTA (N = 908) or to traditional care (N = 462). Approximately 60% of the patients were black, and approximately 54% were women. Traditional care was the usual protocol for each of the 5 study sites, and providers were free to make all decisions for tests and treatments for this group.
In the clinical trial arm, 76% of the cardiac catheterizations were positive compared with 44% in the traditional-care arm. “Clinical trials were identifying patients who needed the cardiac catheterizations more than traditional care,” explained Dr Litt. Revascularization occurred in 2.7% of the clinical trial group and 1.3% of the traditionalcare group, but the difference was not significant.
Resource Utilization
Direct discharge from the emergency department was higher (50% vs 23% for traditional care) and the length of stay was shorter in the overall CTA group (18 hours vs 25 hours), which impacted potential cost-savings. Hospitalization was even shorter, at 12 hours in the negative CTA patients compared with 25 hours with traditional care.
Resource utilization at 30 days was not significantly different between the 2 strategies. A nonsignificant greater number of patients having CTA had a cardiologist visit (7.1% vs 3.8% traditional care).
In-hospital and 30-day cost data are expected within 6 months, with 1-year resource utilization and cost-effectiveness data expected later, including future events, to determine if the CTA strategy remains safe and cost-effective.
Other considerations in terms of cost will be what happens to the patients in whom CAD was identified, which was 3 times higher with CTA than traditional care (9.0% vs 3.5%). The influence on subsequent care is an important question. Will it result in more testing, risk reduction because of changes in lifestyle and medications, or prevention of future events?
Dr Litt noted that radiation exposure with CTA is lower than with SPECT MPI—currently what most patients undergo—and that, as CTA technology improves, its radiation will be reduced. “We are replacing a higher-dose technique with a lower-dose technique,” he pointed out.
The study has been simultaneously published online (N Engl J Med. 2012 Mar 26).