• Anginal symptoms are usually produced by bodily stresses such as exertional and emotional events, and relieved by rest
• ACS is less likely when chest pain is sharp, stabbing, pleuritic, or reproducible with palpation, but still possible (13% of pleuritic chest pain and in 7% of chest pain reproducible with palpation)
• Nitroglycerin may relieve cardiac ischemia, but can also relieve pain in GI and aortic pathology
• A “GI cocktail” of lidocaine and Maalox, or a proton-pump inhibitor such as omeprazole, may relieve GI pathology, but can also relieve reflux in patients with concomitant cardiac ischemia
• Anginal symptoms often last <20 min but >5 min

Often unremarkable

• Cardiac biomarkers:
  • Indicated if the history is suspicious for ACS
  • Should not be elevated in stable angina and may be normal in unstable angina
• Troponin T and I: Starts to rise 2-3 hr after onset of chest pain of ACS and peaks in 8-12 hr. Remains elevated 7-14 d:
  • A single troponin has low sensitivity for ACS (1 study of low-risk chest pain in patients with negative initial troponin: 2.3% rate of AMI and 1% rate of death at 30 d)
  • Timing of biomarker testing is critical: ACEP endorses with “moderate clinical certainty” that a single negative troponin can rule out AMI if drawn 8-12 hr after onset of symptoms. However, uncertainty in time of symptom onset, unreliable history, and possibility of preinfarction angina complicates utilizing single troponin
  • Minor troponin elevations may occur with renal failure, structural heart disease, CHF (acute or chronic), cardiac pacing, pulmonary embolism, sepsis, stroke
  • Lack of stand ardization between assays means labs from one lab cannot always be simply compared to values from another lab. This is important to consider for outside hospital transfers
• High sensitivity troponin are now available in the U.S.:
  • Extremely sensitive
  • May allow earlier and faster recognition of MI
  • May facilitate more rapid treatment
  • Specific for myocardial necrosis
  • Appropriate threshold levels for MI still controversial
• CK/CK-Mb: Less sensitive than troponin, rises more slowly. Little gained by using both CK-Mb and troponin assays. Obtain CK-Mb if
  • Renal failure is present (Tn less accurate)
  • Recent prior infarct
• Myoglobin: Rises faster than stand ard troponin assays and thus able to detect AMI sooner, but max sensitivity is 70%
• B-type natriuretic peptide (BNP):
  • Release and synthesis activated by diastolic ventricular stretch
  • Useful for detecting HF
  • A cutoff of >100 pg/mL diagnosed HF with a sensitivity of 90% and specificity of 76%
  • Unclear significance of elevated BNP in setting of ACS
• The HEART score is a validated decision tool commonly used in the ED to risk stratify patients and identify those who are appropriate for ED discharge. Troponin is measured at 0 and 3 hours to identify patients

• CXR:
  • Usually normal
  • May show cardiomegaly
  • May show pulmonary edema
  • May identify other etiologies of chest pain, such as pneumonia or widened mediastinum of aortic dissection
• Growing data suggest limited utility of stress testing in risk stratification of ED patients, particularly in patients with low likelihood of ACS
• Rest echocardiography:
  • May identify ACS or AMI based on wall motion abnormalities; can also detect pump failure and valvular abnormalities
  • Rest echo has a sensitivity of 70% and specificity of 87% for ACS
  • Rest echo has a sensitivity of 93% and specificity of 66% for AMI
• ⁹⁹Tc (technetium) sestamibi (myocardial perfusion imaging)
  • Radioactive IV dye taken up by myocardium, and detected by single photon emission CT (SPECT) imaging
  • Can be imaged at rest to detect low- or no-flow areas of myocardium; can also be imaged after exercise or pharmacologic stress
  • Per 2009 AHA/ACC guidelines, reserve for intermediate- to high-risk patients
  • Has a sensitivity of 81% and specificity of 73% for ACS
  • Has a sensitivity of 92% and specificity of 67% for AMI
• CT coronary angiography (CTCA):
  • Imaging to evaluate degree of coronary artery stenosis and calcium deposits
  • Negative predictive value between 97-100%, accuracy comparable to stress testing
  • Recent NEJM article suggests CTCA decreases ED length of stay but leads to further downstream testing, radiation exposure, and no decrease in cost of care
• Exercise stress testing (ETT):
  • May help establish diagnosis of angina, provide prognostic information
  • 1-mm depression of the ST-segment in 3 consecutive beats and 2 consecutive leads is characteristic of cardiac ischemia
  • Early positive (within 3 min) stress tests are worrisome for unstable angina
  • 6 min of exercise using a stand ard Bruce protocol suggests an excellent prognosis
  • ETT with ECG alone has a sensitivity of 68% and specificity of 77%
  • ETT with echo has a sensitivity of 85% and specificity of 77%
  • ETT with ⁹⁹Tc (technetium) sestamibi has a sensitivity of 87% and specificity of 64%
  • There is limited utility of cardiac stress testing in patients younger than 40 yr old
• Cardiac catheterization:
  • Considered the gold stand ard for evaluating coronary arteries
  • A history of a recent negative catheterization does not fully exclude AMI, i.e., in cases of vasospasm or cocaine use

ECG, cardiac enzymes, echocardiogram, stress testing

• History suggestive of cardiac etiology for chest pain and ED observation for serial testing unavailable
• Abnormal or changed ECG and ED observation unavailable
• Positive cardiac biomarkers
• Positive rest imaging
• If the diagnosis is unclear, admission to the hospital or an ED observation unit may be useful for serial cardiac biomarkers, ECGs, and further ancillary testing
• Early positive stress test:
  • If the patient has a positive stress test, the decision for admission should be made in consultation with the primary care physician or cardiologist

Patients who meet the following criteria are safe to discharge:

• History not suggestive of cardiac etiology for chest pain
• Normal ECG
• Normal cardiac testing