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Chest Pain

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Assessing Risk of ACS

Missed ACS occurs in setting of chest symptoms and ecg changes.2

History
Presenting with chest pain puts individual at higher risk than historical risk factors 2
History is not sufficiently sufficient to rule in or rule out ACS 2


Research Risk Stratification (Agency for Health Care Policy and Research (AHCPR) guidelines)


High Risk

Intermediate Risk

Low Risk

At least one of the following must be present:
Prolonged ongoing chest pain (>20 minutes)
Pulmonary edema
Angina with new worsening mitral regurgitation murmurs
Rest angina with dynamic ST-segment changes ≥1 mm
Angina with S3 or rales
Angina with hypotension

No high risk features and:
Rest angina now resolved but not low likelihood of CAD
Rest angina (>20 min or relieved with rest or nitroglycerin)
Angina with dynamic T-wave changes
Nocturnal angina
New-onset CCSC III or IV angina in past 2 wk but now low likelihood of CAD
Q waves or ST-segment decrease ≥1 mm in multiple leads
Age >65 y

No high/mid risk features but may have:
Increased angina frequency, severity, or duration
Angina provoked at a lower threshold
New-onset angina within 2 wk to 2 mo
Normal or unchanged ECG results

Diagnostics

Electrocardiogram

Initial ECG is usually nondiagnostic and should be repeated in 30-60 minutes or with change in symptoms. 2
Serial ECG twenty minutes apart had sensitivity of 68.1%.  The difference in sensitivity between serial ECG and initial ECG was statistically significant (p < 0.001).  The specificity of initial ECG and serial ECG monitoring for acute MI were comparable (94.6% vs. 94.8%, difference not significant). 3

Serial ECG Likelihood Ratio:
LR+:13.8
LR-: 0.32

Cardiac Markers

Troponins and MI

Troponins are secondary to ecg changes. 2 High sensitivity Troponins are 94-96% sensitivity at 4h with a negative predictive value of 97-99%. 2 Patients presenting with indeterminate range troponins have a higher likelihood for adverse events, including AMI and need for invasive cardiac procedures. 1 An elevated troponin indicates myocardial damage but does not specify primary ACS as the cause. Infection, pulmonary embolism and other diseases should be considered.

Siemens Troponin I Ultra at Initial Presentation 4
Sensitivity: 97 (91–99)
Specificity: 68 (64–72)

Likelihood Ratios at Presentation Using Siemens Troponin I Ultra
LR+: 3
LR-: 0.04

Troponins and UA

UA is usually defined as new-onset angina, an increase in the frequency and/or duration of angina, or angina at rest. UA throws a bit of a wrinkle into algorithms for ruling out an ischemic source of CP because it only sometimes results in an elevation of cardiac biomarkers. Even with serial troponins, the sensitivity for UA is only 36%.

After Admission
A third troponin may be useful in high risk patients

  1. This article is an excerpt from the book “Avoiding Common Errors in the Emergency Department” (Lippincott Williams & Wilkins, 2010)
  2. Management Strategies for Patients with Low-Risk Chest Pain in the Emergency Department Maame Yaa
  3. Usefulness of Automated Serial 12-Lead ECG Monitoring During the Initial Emergency Department Evaluation of Patients With Chest Pain. Fesmire, F. et. al. Annals of Emergency Medicine (1998), (31): 3-11.
  4. Reichlin T, Hochholzer W, Bassetti S, et al.: Early Diagnosis of Myocardial Infarction with Sensitive Cardiac Troponin Assays. N Engl J Med 2009, 361:858–67
Last Updated September 24, 2011