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Each year, roughly 6 million patients are evaluated for chest pain in emergency departments (ED). Accurate and efficient screening for patients with an acute coronary syndrome is essential. Historically, 2% to 10% of patients with an acute coronary syndrome are inappropriately sent home from the ED. Missed diagnosis of acute myocardial infarction is associated with significant morbidity, and it is the leading contributor to paid malpractice claims paid by emergency physicians. Because of this, almost all patients with chest pain are admitted for further testing. After an average of stay of 36 hours, 70% of these patients show no ischemia with nuclear stress testing and will have ruled out for an acute coronary syndrome. This “overtriage” has enormous economic implications for the US healthcare system with an estimated cost of $8 to $10 billion dollars per year. The emergence of non-invasive coronary 64 slice multidetector computer tomography (MDCT) with its ability to rapidly rule out coronary artery disease in patients with acute chest pain syndromes, enables clinicians to quickly triage and then either admit the patient if significant coronary disease is identified or discharge home if no or minimal coronary disease is seen.

The current MDCT scanners allow for the rapid scanning of the cardiac anatomy, require minimal patient cooperation (breath hold 10 seconds), and have improved spatial (0.5mm vs. invasive angiogram 0.2mm) and temporal resolution (183 – 80ms = single heart beat). Studies comparing MDCT with invasive coronary angiography have shown that MDCT performs well in the detection of significant coronary stenosis, with sensitivities ranging from 82% to 95% and specificities of 82% to 98%. (see fig. 1)

Two separate MDCT randomized control trials looked the ability for MDCT to rule out coronary artery disease as the cause for chest pain in patients presenting to ED were published in the Annals of Emergency Medicine1 involving low risk patients and in Circulation4 involving moderate risk patients. Both studies found MDCT to have a negative predictive valve of 99% and 100% for the identification of acute coronary syndromes in these patients. Additionally in these trials, MDCT was shown to have a higher sensitivity 86% vs. 76%, a greater specificity 92% vs. 90%, and a greater negative predictive valve for future events 99% vs. 97% when compared standard of care (SOC) (24hr hospitalization followed by stress nuclear imaging).

The greater sensitivity of MDCT as compared to nuclear stress testing can be explained by the fact that the presence of coronary calcifications and soft coronary plaques an anatomical findings seen by MDCT are frequent not associated with a significant stenosis but have been shown to be predictive of future cardiac events8. Important autopsy studies in patients with ST elevation myocardial infarctions have shown that the most common coronary plaques that rupture and cause death are usually only 30-40% of the coronary diameter. Given this fact, nuclear stress tests, which only reveal lesions greater the 60%, are likely missing a large number of patients with acute chest pain syndromes who have coronary lesions < 60%. (see fig. 2)

One of the principle advantages of MDCT over the SOC for assessment of acute chest pain in ED patients is how rapidly the coronary disease can be ruled in or ruled out. In a large randomized trial in JACC by Raff, 100 patients received MDCT and 100 patients received the SOC with the average time to rule out coronary artery disease being 3.4 hr with MDCT vs. 15hr with SOC. Both MDCT and SOC were found to be safe (no complications with testing) and accurate (NPV 99-100%) at ruling out coronary disease.

The final advantage of MDCT is its ability to assess non-coronary etiologies of chest pain like pericardial effusion, pericarditis, myocarditis, aortic stenosis, hypertrophic cardiomyopathy, aortic dissection, pleural effusion, pneumonia, hiatal hernia, or pulmonary embolism. MDCT has been shown to identify up to 30% of these non-coronary etiologies in patients presenting to the ED with chest pain syndromes. (see fig. 3)

In summary, the use of MDCT in low risk ED patients with acute chest pain could greatly benefit patients allowing for a more rapid (5 hours vs. 24 hours), and more sensitive assessment for coronary disease, as well as being able to find non-coronary etiologies for chest pain as compared to the current SOC. This will additionally benefit hospitals by opening up patient flow in the ED decreasing admissions of low risk non-acutely ill patients.



Dr. Sander practices at the Orlando Heart Center Sand Lake office and is the Director of Cardiac CT at OHC and Doctor Phillips Hospital. He is board certified in Internal Medicine, is board certified in Cardiovascular Disease, and has completed advanced training cardiac computed tomographic angiography.




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