Highly sensitive troponin and coronary computed tomography angiography in the evaluation of suspected acute coronary syndrome in the emergency department

Abstract

The evaluation of patients presenting to the emergency department with suspected acute coronary syndrome (ACS) remains a clinical challenge. The traditional assessment includes clinical risk assessment based on cardiovascular risk factors with serial electrocardiograms and cardiac troponin measurements, often followed by advanced cardiac testing as inpatient or outpatient (i.e. stress testing, imaging). Despite this costly and lengthy work-up, there is a non-negligible rate of missed ACS with an increased risk of death. There is a clinical need for diagnostic strategies that will lead to rapid and reliable triage of patients with suspected ACS. We provide an overview of the evidence for the role of highly sensitive troponin (hsTn) in the rapid and efficient evaluation of suspected ACS. Results of recent research studies have led to the introduction of hsTn with rapid rule-in and rule-out protocols into the guidelines. Highly sensitive troponin increases the sensitivity for the detection of myocardial infarction and decreases time to diagnosis; however, it may decrease the specificity, especially when used as a dichotomous variable, rather than continuous variable as recommended by guidelines; this may increase clinician uncertainty. We summarize the evidence for the use of coronary computed tomography angiography (CTA) as the rapid diagnostic tool in this population when used with conventional troponin assays. Coronary CTA significantly decreases time to diagnosis and discharge in patients with suspected ACS, while being safe. However, it may lead to increase in invasive procedures and includes radiation exposure. Finally, we outline the opportunities for the combined use of hsTn and coronary CTA that may result in increased efficiency, decreased need for imaging, lower cost, and decreased radiation dose.

Keywords: Acute chest pain; Acute coronary syndrome; Coronary computed tomography angiography; Highly sensitive troponin.

Figure 1

Simplified algorithm for the management of patients with suspected acute coronary syndrome based on European Society of Cardiology guidelines.

Figure 2

Simplified algorithm for the management of patients with suspected acute coronary syndrome based on American Heart Association/American College of Cardiology guidelines.

Figure 3

The diagnostic performance of highly sensitive troponin (red bars) when compared with conventional troponin (blue bars) for acute myocardial infarction in patients presenting <3 and >3 h of chest pain onset (adapted from Body et al.). Highly sensitive troponin assay provides significantly improved sensitivity for the detection of myocardial infarction in patients presenting within 3 h of chest pain onset. There is no difference in the specificity in those who present <3 or >3 h of chest pain onset.

Figure 4

Length of stay and proportion of patients discharged in the Rule Out Myocardial Infarction/Ischemia Using Computer Assisted Tomography II trial. The cumulative frequency of discharges from the index visit according to the length of stay is shown. The horizontal line indicates the median length of stay in the two study groups, which was significantly different (8.6 h in the coronary computed tomography angiography vs. 26.7 h in the standard-evaluation group, P < 0.001). Reprinted with permission from Hoffmann et al.

Figure 5

The association of significant stenosis and high-risk plaque features with the probability of acute coronary syndrome in the Rule Out Myocardial Infarction/Ischemia Using Computer Assisted Tomography II trial. Stenosis ≥50%: severe stenosis of the mid-left anterior descending coronary artery (red arrow). Positive remodelling: non-calcified plaque with positive remodelling in the distal right coronary artery. The two-dotted red lines demonstrate the vessel diameters at the proximal and distal references (both 1.8 mm), and the solid red line demonstrates the maximal vessel diameter in the mid-portion of the plaque (2.7 mm). The remodelling index is 1.5. Low Hounsfield units plaque: partially calcified plaque in the mid-right coronary artery with low <30 Hounsfield unit plaque. The red circles demonstrate the three regions of interest, with mean computed tomography numbers of 22, 19, and 20 Hounsfield units. Napkin-ring sign: napkin-ring sign plaque in the mid-left anterior descending coronary artery. Schematic cross-sectional view of the napkin-ring sign. The red line demonstrates the central low Hounsfield unit area of the plaque adjacent to the lumen (yellow ellipse) surrounded by a peripheral rim of the higher computed tomography attenuation (red arrows). Spotty calcium: partially calcified plaque in the mid-right coronary artery with spotty calcification (diameter <3 mm in all directions; red circles). Reprinted with permission from Puchner et al.

Figure 6

Possible implementation of highly sensitive troponin and coronary computed tomography angiography in the evaluation of patients with suspected acute coronary syndrome in the emergency department.