AJR: Cardiac CT triage scores a triple

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Researchers suggested links between cardiac CT triage and three key benefits—fewer invasive catheterizations, improved survival and reduced costs—in a simulation model of the clinical and economic outcomes of low-risk patients with acute chest pain in the emergency department, according to a study published in the April issue of the American Journal of Roentgenology.

The clinical workup of patients who present to the ED with acute chest pain is somewhat problematic. A fraction of these patients have acute coronary syndrome (ACS), which manifests with atypical symptoms that overlap with other clinical conditions. The American College of Cardiology and American Heart Association recommend hospitalization for low-to-intermediate risk patients with initial negative ECG and enzyme test results, posing a hefty economic burden as these patients accounted for two million ED visits in 2004, shared Alexander Goehler, MD, of the Institute for Technology Assessment at Massachusetts General Hospital in Boston, and colleagues.

The authors constructed a simulation model to estimate the clinical and economic outcomes of cardiac CT angiography (CTA) compared with the standard of care for low-risk ED patients with acute chest pain. “Specifically, we wanted to model the number of patients correctly and incorrectly referred to invasive coronary angiography, the number with ACS who were incorrectly diagnosed, the 30-day mortality rate, and the overall costs of diagnostic workup and subsequent revascularization during a 30-day period,” wrote Goehler.

The researchers expanded a previously published model based on a cohort of 1,000 55-year-old patients presenting to the ED with acute chest pain, low ACS risk, initial negative biomarkers and nonsignificant ECG changes. Goehler and colleagues modeled possible diagnostic pathways from presentation to clinical outcome for the standard of care and CTA approaches.

In one pathway, the research team employed SPECT as the standard noninvasive diagnostic study. Goehler and colleagues determined that coronary CTA-based triage would lead to immediate discharge for 706 patients and reduce the number of patients referred for invasive coronary angiography from 406 under the standard of care with SPECT imaging to 255 patients. Further, the CTA pathway reduced “missed” ACS cases from 18 with SPECT imaging to five. Finally, in the standard of care model, 255 patients sent to invasive coronary angiography ultimately had no coronary artery disease. CTA dropped this group to 67 patients, according to the authors.

The CTA triage model also cut costs in the ED phase and over the 30-day period, producing an average savings of $851 and $283 per patient, respectively.

Goehler and colleagues considered the impact of employing stress echocardiography rather than SPECT as the standard noninvasive diagnostic test. The stress echo standard reduced the number of patients referred for invasive angiography and those diagnosed with coronary artery disease while decreasing the number of patients with missed ACS.

However, employing stress echo rather than SPECT in the standard of care model reduced ED cost savings to $462 per patient and resulted in 30-day treatment costs $208 more expensive per patient at $4,858 for the standard of care model and $5,066 for the CTA model.

The authors explained that their results were consistent with previous cost-effectiveness analyses and suggested that “coronary CTA would have the highest impact in a population with low CAD prevalence.” They cautioned against extrapolating the results to a lower risk population as the model did not target this group.

The researchers acknowledged several limitations to the model. Specifically, they did not incorporate the effects of incidental findings or estimate the impact of radiation exposure. Nor did they explore increased risks of post-discharge death due to other causes. They also assumed all patients would be eligible for CTA and that the study would be available 24/7.

“Despite its limitations, our model supports our hypothesis suggesting that coronary CTA may be a valuable addition to the management of low-to-intermediate risk chest pain patients in the ED,” Goehler and colleagues concluded.