1. Risk-stratify patients who present with chest pain in the ED.

2. Discuss the value and limitations of history and physical examinationwhen evaluating patients with chest pain.

3. Perform appropriate tests to exclude acute myocardial infarction, unstable angina, aortic dissection, and pulmonary embolism.

4. Describe the role of noninvasive testing for patients who present to the ED with chest pain.

5. Adequately document studies, findings, and acceptable risk before discharging patients with low-risk chest pain.

Four Basic Questions

Missed diagnosis: of patients who present to emergency department (ED) with acute coronary syndrome (ACS), diagnosis missed in only 1% to 2% of cases; but large volume (1.2 million cases of acute myocardial infarction [AMI] and 1.2 cases of unstable angina [UA] each year) translates to 10,000 to 20,000 missed cases of ACS annually (leading cause of malpractice claims against ED physicians)

Important questions to answer: 1) was AMI adequately excluded? 2) was UA adequately excluded? 3) were other life-threatening causes of chest pain (eg, pulmonary embolism [PE], aortic dissection) excluded? 4) was charting adequate?

Case 1: man, 46 yr of age, complains of chest pain and headache; chest pain had relatively sudden onset during previous night, and described as “golf ball-sized” in left side of chest; pain does not radiate and has been constant, but decreasing; headache onset in morning; medical history—migraines (patient reports response to morphine); previous visits to ED because of migraines and abdominal pain (patient became confrontational about pain medications during past visit); patient smokes and has untreated hypertension and lipidemia; work-up—no abnormal findings on physical examination, electrocardiography (ECG), or laboratory tests (including troponin level); treatment and follow-up—symptoms resolved with ibuprofen and morphine; outpatient treadmill test scheduled

Value and Limitations of History and Physical Examination

Risk stratification: reviewed by Panju et al (1998) and Swap and Nagurney (2005)

Patient characteristics: risk for ACS increases with diabetes, history of MI, male sex, and advanced age (most predictive factor)

Signs and symptoms: increased risk for ACS—radiation to left or right arm, neck, or jaw; pain increases with exertion; nausea, vomiting, or diaphoresis; symptoms similar to previous MI; pain described as pressure-like; of these, only radiating pain substantially increases suspicion for MI (likelihood ratio [LR] \>3.0; LR of 10 considered diagnostic); decreased risk for ACS—pleuritic pain; pain reproducible with palpation or movement; sharp or stabbing pain; presence decreases but does not eliminate suspicion for MI (LR ≈0.3; LR of 0.1 effectively rules out diagnosis)

Classic angina: textbook description—substernal pain, pressure, or squeezing; associated nausea, diaphoresis, or shortness of breath; symptoms relieved with rest and with nitroglycerin; caveat—studies have shown no predictive value of response or lack of response to nitroglycerin

Atypical presentations: 30% to 50% of patients with AMI present without chest pain; of these, many have shortness of breath as primary complaint; risk factors—history of heart failure or stroke increases risk most; advanced age and diabetes also increase risk; female sex, although often associated with atypical presentations, confers little to no additional risk, once controlled for age at presentation

Lessons from missed AMI: review of 10,000 patients with suspected ACS evaluated in ED found 0.2% of discharged patients had undiagnosed AMI and 0.4% had undiagnosed ACS; atypical presentation increased likelihood of missing diagnosis; atypical presentations common; history and physical examination insufficient to exclude ACS but helpful for risk stratification

Electrocardiography

Cardiac ischemia: significantly increases LR for AMI or UA; important to recognize and admit all patients with ischemic ECG; study found ≈25% of patients with undiagnosed AMI had unrecognized ischemia on ECG, and 10% to 25% had recognized ischemia; absence of ischemia—helpful for risk stratification, but does not exclude AMI (LR ≈0.3); patients with AMI and normal ECG have high risk for adverse events (AEs); ≤10% of patients with AMI have normal ECG; risk for cardiac event or death—study findings show risk ≈20% among patients who have AMI with normal findings on ECG; risk 35% among patients who have AMI with diagnostic ST elevations or depressions

Serial ECGs: useful for identifying ischemia; American College of Cardiology/American Heart Association (ACC/ AHA) recommends initially performing at 15- to 30-min intervals; benefits—simple and inexpensive; increase detection of ischemia

Cardiac Markers

Patients who present \>8 hr after symptom onset: single negative test for cardiac markers sufficient to exclude AMI (in patients with constant [ie, not stuttering] symptoms)

Patients who present <8 hr after symptom onset: 1) initial measurement of troponin or creatinine kinase MB (CK-MB) levels (to exclude infarct during presentation), repeated 8 hr from onset (to exclude AMI); 2) initial measurements of myoglobin and troponin or CK-MB, repeated 90 min later (exclude AMI if both negative); 3) measurements of CK-MB and troponin levels at baseline and at 2 hr (exclude AMI if levels do not increase); comment—speaker gives patient aspirin while waiting, provided patient not allergic

Slight elevations in troponin levels: increase risk for AEs; levels of 0.1 to 0.4 ng/mL associated with odds ratio of 2.5 for death or MI; implication of levels <0.1 ng/mL unknown; decreased suspicion—troponin levels slightly elevated and do not increase after 3 to 4 hr; patients with multiple visits to ED (followed by admission to hospital) due to similar complaints and similarly low elevations in troponin levels, but no history of AMI (suggests chronic elevation)

Conclusions: generally, clinicians can reliably and safely exclude AMI in ED; more likely to miss UA than AMI (but patient may suffer AMI after discharge); return to case—AMI adequately excluded (troponin level negative in \>8 hr of constant pain)

Stenosis and MI: MIs frequently caused by moderately obstructive plaques (eg, plaques that obstruct <50% of arterial diameter); risk for plaque disruption depends more on plaque type than on degree of stenosis; noninvasive testing (to rule out UA) identifies stenosis, not AMI

Noninvasive Testing

Sensitivity: outpatient data from cardiology departments—exercise stress test (treadmill) 68% sensitive; nuclear stress test 88% sensitive; stress echocardiography ≈75% sensitive; sensitivity defined relative to identifying rate- limiting coronary artery disease; ED experience—noninvasive tests used to identify active obstruction; for this purpose, treadmill testing has sensitivity of 98%

Exercise stress testing: study of 1000 patients at relatively low risk for ACS who underwent treadmill test (troponin unavailable for some; speaker recommends obtaining troponin before treadmill); 2.4% of participants had ACS (AMI or need for urgent revascularization); negative treadmill results have high negative predictive value for ACS; positive results have high positive predictive value for ACS; nondiagnostic results associated with increased risk for cardiac events (3.6% vs 2.4% of all participants); criteria for diagnostic test—patient must reach 85% maximum predicted heart rate (MPHR) or 10 metabolic equivalents (mets); if criteria not met, test considered nondiagnostic (patient at elevated risk for ACS)

Predictive value of previous treadmill test: history of positive test increases risk for AEs; history of negative (normal) test does not decrease risk (relative to patient who has never undergone stress testing)

Interpretation of results: use treadmill—to evaluate whether current event causes acute ischemia (does not predict future events); to assess exercise tolerance; exclusion—if pain and symptoms do not increase with exercise and if ischemia does not develop, acute event effectively ruled out

Delayed testing: for low-risk patients, ACC/AHA recommends noninvasive testing within 72 hr of visit to ED; safe strategy for low-risk patients, if stress testing not available in ED; return to case—patient scheduled for treadmill test on outpatient basis; sufficient to evaluate UA in low-risk patient (if done within 72 hr)

Computed tomography (CT) angiography: used like noninvasive test to exclude UA, not AMI; positive results—\>50% stenosis; presence of soft noncalcified atherosclerotic plaque; high calcium score; advantage over treadmill—visualizes high-risk plaques; requirements—advanced scanner (64-detector best; artifacts less likely); gated imaging (captures image at same point in cardiac cycle); metoprolol to slow heart rate (easier to capture image); sublingual nitroglycerin to dilate and improve visualization of blood vessels; secure, proximal intravenous (IV) line to deliver high-pressure bolus; sensitivity—few studies in ED setting; informal review of literature shows average sensitivity of ≈98%; disadvantages—exposure to contrast (risk for renal toxicity and allergic reaction); radiation exposure; 10% of tests have uninterpretable findings (may lead to increased testing); not suitable for unstable patients

Radiation exposure: ≈10 mSv in men; ≈15 mSv in women; annual exposure to background radiation, 3 mSv; cardiac catheterization exposes patient to 6 mSv of radiation; nuclear (technetium sestamibi) stress testing exposes patient to 8 mSv; increased risk for cancer—small, relative to background rate of cancer

Conclusions: treadmill test preferred when available (no radiation exposure; 99.8% predictive); CT angiography good option if treadmill unavailable or patient unable to exercise; most appropriate for patients at moderate risk; also identifies aortic dissection and (sometimes) PE

Charting

Defensive charting: inevitable to miss disease and discharge patient who may then have adverse outcome; defensive charting protects clinician in case of litigation; document steps to exclude AMI, UA, aortic dissection, and PE

Exclusion of AMI: document troponin level (measured in accordance with recommendations) and appropriate response to ECG findings of ischemia

Exclusion of UA: document findings of noninvasive testing (or referral in appropriate patients); document findings, risk (eg, acceptably low for discharge), patient instructions, and scheduled follow-up

Exclusion of aortic dissection: document absence of evidence, based on eg, imaging, symptoms, pulses

Exclusion of PE: document absence of risk factors (eg, unexplained pleuritic chest pain, shortness of breath, unilateral edema); order D-dimer test in appropriate patients (rules out PE)

More pearls: risk for disease is never zero but may be acceptable for discharge (document accordingly); avoid labeling chest pain as “noncardiac” or “gastroesophageal reflux disease (GERD)”, but document reasons for suspicion

Return to case: AMI and UA adequately excluded, but aortic dissection not excluded (chest x-ray recommended)

Summary: atypical presentations common; evaluating more patients results in fewer missed diagnoses; establishing guideline-based protocols may speed evaluation process; patients with ischemic findings on ECG always require further evaluation; appropriate use of cardiac markers effectively excludes AMI; noninvasive testing required to exclude UA