2015 ACR/ACC/AHA AUC for Cardiovascular Imaging in ED Chest Pain — Quick Reference

Overview: Appropriate Use Criteria in ED Chest Pain

This 2015 Appropriate Utilization Criteria (AUC) document applies a standardized rating system to guide cardiovascular imaging in ED patients with chest pain (CP). Each clinical scenario receives an appropriateness rating:

Appropriateness Rating Scale

Appropriate (A): Benefits generally outweigh risks; reasonable option for patient management.
May Be Appropriate (M): Benefits and risks variable; appropriate based on clinical judgment and patient preferences.
May Be Appropriate by Consensus (M*): Consensus reached despite limited evidence; use when specific data unavailable.
Rarely Appropriate (R): Risks outweigh benefits; lack of clear clinical advantage; rarely justified except in unusual circumstances.

Document Scope

This document focuses on imaging in the initial ED evaluation of patients with suspected:

Acute Coronary Syndrome (ACS) — including STEMI and NSTEMI
Pulmonary Embolism (PE)
Acute Aortic Syndrome (AAS) — aortic dissection, intramural hematoma, penetrating ulcer
Other life-threatening conditions identified by history, exam, and initial ECG

Imaging decisions balance rapid diagnosis with radiation exposure and resource utilization. For all patients, initial assessment includes history, physical examination, 12-lead ECG, and biomarker analysis (troponin ± d-dimer).

Risk Stratification in the ED

Use risk categories to organize clinical scenarios. Apply the following scoring tools to rapidly categorize patients:

HEART Score (Acute Coronary Syndrome)

Use the HEART Score calculator to assess short-term 30-day MACE risk in suspected ACS:

High risk (HEART ≥7): ≥17% MACE risk — admit, treat urgently
Intermediate risk (HEART 4–6): 2–16% MACE risk — observation vs. admission
Low risk (HEART ≤3): <2% MACE risk — safe discharge if troponin negative

TIMI Risk Score (NSTEMI/Unstable Angina)

Use the TIMI Risk Score for ACS without STEMI:

Low risk (0–2): ~5% 14-day event rate
Intermediate risk (3–4): ~8–13% 14-day event rate
High risk (≥5): ~19% 14-day event rate

Wells PE Score (Pulmonary Embolism)

Use the Wells PE Probability Score for suspected PE:

Low probability (<2 points): ~1.3% PE risk
Intermediate probability (2–6 points): ~16% PE risk
High probability (>6 points): ~37% PE risk

GRACE ACS Score (Mortality Risk)

Use the GRACE ACS Risk Calculator to estimate in-hospital and 6-month mortality in confirmed ACS.

Imaging for STEMI & Clearly Noncardiac Diagnosis

Clinical Scenario 1: When Diagnosis is Clear from Initial Workup

When 12-lead ECG shows STEMI, or initial history/exam clearly identifies noncardiac cause (pneumothorax, pneumonia, costochondritis), imaging decisions are straightforward:

Indication	Chest X-ray	Echo	SPECT	CCTA	CCath
Diagnostic ECG for STEMI	R	R	R	R	A
Noncardiac diagnosis evident (pneumonia, esophageal rupture, costochondritis)	R	R	R	R	R

Key Point: In STEMI, proceed directly to coronary catheterization. Diagnostic imaging delays reperfusion. In clearly noncardiac cases, no cardiac imaging is needed.

Imaging in Suspected NSTEMI & ACS

When ACS is suspected but ECG is not diagnostic, imaging helps risk-stratify and guide management. Two pathways are recognized:

Pathway A: Early Assessment (Serial Troponin + Early Imaging)

For patients with low-to-intermediate pretest probability:

Clinical Scenario	Echo Rest	CMR Rest	SPECT Rest	CCTA	CCath
Unequivocal ischemia on ECG/biomarker	R	R	R	R	A
Equivocal ECG or single troponin	M*	M*	A	A	R
Ischemic symptoms resolved >2–3 hours; initial troponin negative	R	M	M*	A	R
Low risk (HEART ≤3); normal initial troponin; no symptoms	R	R	A	A	R

Pathway B: Observational (Serial Troponin at Rest)

For observation-admitted patients with negative serial markers:

Clinical Scenario	Exercise ECG	Stress Echo	Stress SPECT	CCTA	CCath
Serial troponins positive for NSTEMI	R	R	R	R	A
Serial troponins negative; ECG unchanged	A	A	A	M*	A
Serial troponins negative; ongoing ischemic symptoms	A	A	A	A	R

Imaging Modalities for ACS

Coronary CT Angiography (CCTA)

Rapid imaging with excellent sensitivity (≥95%) and NPV (≥98%):

Appropriate in low-to-intermediate risk with equivocal/resolved symptoms
Timing: Can perform within 2–3 hours; early CCTA reduces length of stay
Advantage: Identifies coronary anatomy and alternative diagnoses (aorta, PE)

Stress Echocardiography

Real-time wall motion assessment during exercise/pharmacologic stress:

Appropriate for intermediate-risk with negative troponin
Advantage: No radiation; assesses valve pathology
Limitation: Requires cooperation; operator dependent

Resting Echocardiography

Detects wall motion abnormalities, LV function, valve disease:

Limitation: Normal echo does not exclude obstructive CAD
Most useful when abnormal wall motion is detected

SPECT Myocardial Perfusion Imaging

Resting SPECT uses radiotracer (Tc-99m) to assess perfusion:

Appropriate for detecting acute ischemia; identifies hypoperfused regions
Advantage: Direct perfusion assessment
Limitation: Radiation; delayed results

Cardiac MRI (CMR)

Excellent tissue characterization and perfusion imaging:

May Be Appropriate (M*) for selected equivocal cases
Limitation: Time-intensive; limited 24/7 availability

Pearl: In low-risk patients with negative high-sensitivity troponin at 3 hours, CCTA with NPV ~99% enables safe discharge.

Pitfall: Single troponin result does not rule out ACS. Serial troponin (2–3 hours) is standard; high-sensitivity troponin may require 1–3 hours.

Imaging in Suspected Pulmonary Embolism

Risk-stratify using the Wells PE Score, d-dimer, and biomarkers:

Clinical Scenario	CTPA	Compression US	VQ Scan	PMRA
Low probability; d-dimer negative	R	R	R	R
Intermediate-to-high probability	A	M	A	R
Hemodynamically unstable	A	A	R	R

Imaging Modalities for PE

CT Pulmonary Angiography (CTPA)

Sensitivity: 90–98% for lobar/central PE; lower for subsegmental
First-line in most EDs; identifies alternative diagnoses
Radiation: ~2–3 mSv

Compression Ultrasound (CompUS)

Detects DVT proximal to knee with ~95% sensitivity
May Be Appropriate if CTPA delayed/unavailable

Ventilation-Perfusion (VQ) Scan

Appropriate with normal chest X-ray and intermediate-high pretest probability
Limitation: High indeterminate rate with lung disease

Pearl: In pregnancy, PE is a leading maternal cause of death. VQ scan preferred if normal CXR; CTPA acceptable if high suspicion.

Imaging in Suspected Acute Aortic Syndrome

Aortic dissection, intramural hematoma, and penetrating ulcer present with sudden, severe, tearing chest/back pain. High mortality if not rapidly diagnosed.

Clinical Scenario	CTAo	MRAo	TEE	AoCath
Hemodynamically unstable	A	M*	M*	M*
Stable, no prior aortic intervention	A	A	M	R
Stable, prior aortic intervention	A	A	M	M*

Imaging Modalities

CT Aortography (CTAo)

Sensitivity/Specificity: >95% for dissection and intramural hematoma
First-line; rapid (<5 min); identifies alternatives

MR Aortography (MRAo)

Superior tissue characterization; ~98% sensitivity
Second-line due to time (30–40 min); contraindicated in unstable patients

Transesophageal Echocardiography (TEE)

Bedside capability; ~95–99% sensitivity for proximal dissection
Assesses aortic regurgitation and pericardial effusion

Pitfall: Do not delay AAS diagnosis with serial imaging. If high clinical suspicion, proceed to CTAo or TEE immediately.

"Triple Rule-Out" (TRO) CTA for Unclear Diagnosis

When likelihood of ACS, PE, and AAS are all uncertain after initial workup:

Clinical Scenario	TRO CTA
Overall likelihood of ACS, PE, AAS is low	R
Overall likelihood of ACS, PE, AAS is not low	A

Note: TRO CTA has higher radiation and contrast dose. Use when differential truly spans all three diagnoses.

Clinical Pearls & Pitfalls

DO: Risk Stratify First

Use HEART, TIMI, and Wells scores before imaging selection
Serial troponin (not single value) required for ACS rule-out
Negative d-dimer in low-probability PE effectively excludes diagnosis

DON'T: Order Imaging Blindly

Avoid CCTA/SPECT in high-risk ACS (positive troponin, ischemic ECG) — proceed to cath
Do not obtain CTPA in low-probability PE without d-dimer elevation
Avoid serial imaging without clinical reason

Pearl: High-sensitivity troponin enables earlier ACS rule-out (1–3 hours). Know your institution's protocol and cutoffs.

Pitfall: Normal resting echo or SPECT does not exclude ischemia if patient not symptomatic during test.

Pearl: CCTA is increasingly used as ED "gatekeeper" test. Negative CCTA in low-risk patients safely excludes CAD and enables discharge.

Pitfall: Coronary calcium score (CCath) has no role in acute ACS. Zero score does not exclude significant CAD in symptomatic patients.

Pearl: In pregnancy, PE remains leading maternal cause of death. VQ preferred if normal CXR; CTPA acceptable if high suspicion. MR angiography is alternative.

Pitfall: Do not delay AAS diagnosis with serial testing. High clinical suspicion = proceed directly to CTAo or TEE.

Related Calculators & Risk Scores

Apply these tools to risk-stratify ED chest pain patients and guide imaging decisions:

2015 ACR/ACC/AHA AUC for Cardiovascular Imaging in ED with Chest Pain