Coronary Artery Calcium Testing Helps Rule Out ACS in the ED
Key findings
- A Mass General study found that combining coronary artery calcium (CAC) testing with Thrombolysis in Myocardial Infarction (TIMI) score can better rule out acute coronary syndrome (ACS) than use of TIMI alone for symptomatic patients presenting at the ED
- 100% negative predictive value (NPV) for the diagnosis of ACS occurred by combining TIMI and CAC compared to 94.5% for TIMI or 99.5% for CAC alone
- 89.0% NPV occurred for the presence of plaque or stenosis by combining TIMI and CAC scores compared to 55.8% for TIMI or 88.7% for CAC alone
- The extent of CAC was strongly associated with incidence of ACS and severity of CAD
- CAC was concluded to be a valuable add on to TIMI for patients suspected of ACS in emergency centers because it is quick and does not require a cardiologist or radiologist to perform
Many patients arrive at the emergency department (ED) with suspected acute coronary syndrome (ACS) but are not actually at high risk. To improve ACS assessment, a team led by Brian Ghoshhajra, MD, MBA, service chief of Cardiovascular Imaging, evaluated the usefulness of the negative predictive value (NPV) of incorporating coronary artery calcium (CAC) testing to a Thrombolysis in Myocardial Infarction (TIMI) risk score, compared to each test alone.
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The single center study reported in the International Journal of Cardiology followed 826 consecutive patients presenting to the ED with symptoms of ACS but no known coronary artery disease or elevated serum biomarkers. They received non-contrast ECG-gated coronary CT for a CAC score, and CT angiography (CTA) to identify any coronary stenosis. A board-certified radiologist or cardiologist evaluated the degree of stenosis as follows:
- Normal: no plaque or stenosis
- Mild: stenosis at 1-49%
- Moderate: stenosis at 50-69%
- Severe: stenosis ≥70%
A TIMI risk score was also calculated.
The primary endpoint was ACS as evidenced as myocardial infarction (MI) and unstable angina during hospitalization based on a cardiologist’s review of clinical data including medical record history, and laboratory and ECG results. The secondary endpoint was a finding of significant CAS as defined as either ≥50% stenosis in the left main or ≥70% stenosis in other major epicardial vessels.
Importantly, combining TIMI and CAC scores offered the best path to rule out ACS. Specifically, 100% was the NPV for patients for ACS compared to 94.5% or 99.5% for the use of TIMI and CAC scores, respectively.
Other findings of note include:
- 89.0% was the NPV for combined TIMI and CAC scores for detecting the presence of any plaque or stenosis compared to 55.8% for using TIMI or 88.7% for CAC alone
- 99.7% was the NPV observed at the 50% stenosis level when TIMI was combined with CAC, compared with 88.9% for TIMI and 99.5% for CAC score alone
- 100% was the NPV at a 70% stenosis level when TIMI was combined with CAC as compared to 93.7% for TIMI or 99.8% for a CAC score alone
CAC scores, which are known to evidence coronary atherosclerosis, stratified so that increases aligned with rises in the number of patients with greater levels of stenosis. As CAC scores moved from 0 to N440, the percentage in the ≥50% stenosis group rose from 0.9% to 74.0% and, in the ≥70% stenosis group, from 0.7% to 44.0%.
Only 10% of patients found without CAC had any coronary plaque by CTA, two patients (0.5%) were diagnosed with MI and no person had unstable angina. By contrast, for those with a TIMI of 0, 44% had plaque present on CTA.
CAC was concluded to be a valuable add on to TIMI for patients suspected of ACS in emergency centers because it is quick and does not require a cardiologist or radiologist to perform. Further, it can be used when more advanced testing methods are not available.
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