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Emergency and Acute Medicine – Cardiac Testing
Overview
Cardiac testing is essential in emergency patients with concern for acute coronary syndrome (ACS) or heart failure (HF). These entities exist on a continuum, where unstable angina may progress to myocardial infarction and subsequently to heart failure. Missed ACS remains a major source of emergency department malpractice, with a small but significant percentage of ACS patients discharged inappropriately. History, physical examination, and ECG are the foundation of evaluation but fail to detect a minority of myocardial infarctions, necessitating adjunctive testing such as biomarkers and imaging.
Underlying Causes
ACS most commonly results from atherosclerotic coronary artery disease or coronary vasospasm. In pregnancy, spontaneous coronary artery dissection should be considered when ischemic ECG changes accompany chest pain.
Clinical Presentation
Anginal discomfort is typically provoked by exertion or emotional stress and relieved by rest. Chest pain described as sharp, stabbing, pleuritic, or reproducible by palpation is less suggestive of ACS, though ischemia can still be present in a minority of these cases. Symptom relief with nitroglycerin or gastrointestinal treatments does not reliably distinguish cardiac from noncardiac causes. Anginal episodes often last more than 5 minutes but less than 20 minutes; symptoms persisting beyond 20 minutes raise concern for unstable angina or infarction. Physical examination is frequently normal.
Core Emergency Evaluation
A 12-lead ECG should be obtained within 10 minutes of arrival for patients with chest pain. A single ECG may miss up to half of acute myocardial infarctions, as changes can evolve over time. Hyperacute T waves may represent the earliest ischemic sign. Continuous ECG monitoring or repeat ECGs within 15–60 minutes improves detection. ST-segment depression of 1 mm suggests ischemia, while ST elevation greater than 1–2 mm in contiguous leads defines STEMI. New left bundle branch block complicates diagnosis; concordant ST changes using Sgarbossa criteria increase suspicion. Additional ECG leads may identify infarctions not seen on standard views, including right ventricular and posterior wall involvement.
Laboratory Assessment
Cardiac biomarkers are indicated when ACS is suspected. Troponin I and T rise within 2–3 hours, peak by 8–12 hours, and remain elevated for days. A single negative troponin has limited sensitivity unless drawn 8–12 hours after symptom onset. Mild elevations may occur in nonischemic conditions such as renal failure, sepsis, pulmonary embolism, or heart failure. CK-MB is less sensitive and generally adds little unless renal failure or recent infarction limits troponin interpretation. BNP assists in diagnosing heart failure, with levels above 100 pg/mL supporting the diagnosis.
Imaging Modalities
Chest radiography is often normal but may reveal cardiomegaly, pulmonary edema, pneumonia, or mediastinal widening. Rest echocardiography can identify wall motion abnormalities and pump failure, providing moderate sensitivity for ACS and higher sensitivity for myocardial infarction. Myocardial perfusion imaging using technetium-99m sestamibi detects regions of reduced perfusion and is reserved for intermediate- to high-risk patients. CT coronary angiography offers a high negative predictive value but may increase downstream testing without reducing cost. Exercise stress testing provides diagnostic and prognostic information, with enhanced accuracy when combined with echocardiography or nuclear imaging. Cardiac catheterization remains the gold standard for coronary assessment but does not exclude vasospasm-related events.
Prehospital and Initial ED Management
Prehospital ECG monitoring improves early detection of ACS. In the emergency department, continuous cardiac monitoring and pulse oximetry are standard. Further management depends on risk stratification and test results.
Diagnostic Strategy in the ED
Patients with concerning history should undergo ECG and initial troponin testing. Abnormal findings warrant admission and cardiology consultation. Persistent symptoms or evolving ECG changes necessitate repeat testing or advanced imaging. Low- to moderate-risk patients may undergo stress testing, either during observation or as an outpatient within 72 hours if reliable follow-up exists. Abnormal ancillary testing requires admission or specialty consultation.
Disposition Planning
Admission is indicated for patients with abnormal ECGs, positive biomarkers, concerning imaging, or unavailable observation resources. Observation units may be used for serial testing when diagnosis is uncertain. Discharge is appropriate for patients with noncardiac histories, normal ECGs, and negative cardiac testing.
Follow-Up Considerations
Abnormal stress tests require close cardiology follow-up. Patients discharged with undifferentiated chest pain should have timely outpatient evaluation if inpatient testing is deferred.
Clinical Insights and Cautions
A normal ECG or troponin does not exclude coronary artery disease. Serial ECGs and additional leads increase diagnostic sensitivity. Most emergency patients with undifferentiated chest pain require some form of additional cardiac testing to safely exclude ACS.
Overview
Cardiac testing is essential in emergency patients with concern for acute coronary syndrome (ACS) or heart failure (HF). These entities exist on a continuum, where unstable angina may progress to myocardial infarction and subsequently to heart failure. Missed ACS remains a major source of emergency department malpractice, with a small but significant percentage of ACS patients discharged inappropriately. History, physical examination, and ECG are the foundation of evaluation but fail to detect a minority of myocardial infarctions, necessitating adjunctive testing such as biomarkers and imaging.
Underlying Causes
ACS most commonly results from atherosclerotic coronary artery disease or coronary vasospasm. In pregnancy, spontaneous coronary artery dissection should be considered when ischemic ECG changes accompany chest pain.
Clinical Presentation
Anginal discomfort is typically provoked by exertion or emotional stress and relieved by rest. Chest pain described as sharp, stabbing, pleuritic, or reproducible by palpation is less suggestive of ACS, though ischemia can still be present in a minority of these cases. Symptom relief with nitroglycerin or gastrointestinal treatments does not reliably distinguish cardiac from noncardiac causes. Anginal episodes often last more than 5 minutes but less than 20 minutes; symptoms persisting beyond 20 minutes raise concern for unstable angina or infarction. Physical examination is frequently normal.
Core Emergency Evaluation
A 12-lead ECG should be obtained within 10 minutes of arrival for patients with chest pain. A single ECG may miss up to half of acute myocardial infarctions, as changes can evolve over time. Hyperacute T waves may represent the earliest ischemic sign. Continuous ECG monitoring or repeat ECGs within 15–60 minutes improves detection. ST-segment depression of 1 mm suggests ischemia, while ST elevation greater than 1–2 mm in contiguous leads defines STEMI. New left bundle branch block complicates diagnosis; concordant ST changes using Sgarbossa criteria increase suspicion. Additional ECG leads may identify infarctions not seen on standard views, including right ventricular and posterior wall involvement.
Laboratory Assessment
Cardiac biomarkers are indicated when ACS is suspected. Troponin I and T rise within 2–3 hours, peak by 8–12 hours, and remain elevated for days. A single negative troponin has limited sensitivity unless drawn 8–12 hours after symptom onset. Mild elevations may occur in nonischemic conditions such as renal failure, sepsis, pulmonary embolism, or heart failure. CK-MB is less sensitive and generally adds little unless renal failure or recent infarction limits troponin interpretation. BNP assists in diagnosing heart failure, with levels above 100 pg/mL supporting the diagnosis.
Imaging Modalities
Chest radiography is often normal but may reveal cardiomegaly, pulmonary edema, pneumonia, or mediastinal widening. Rest echocardiography can identify wall motion abnormalities and pump failure, providing moderate sensitivity for ACS and higher sensitivity for myocardial infarction. Myocardial perfusion imaging using technetium-99m sestamibi detects regions of reduced perfusion and is reserved for intermediate- to high-risk patients. CT coronary angiography offers a high negative predictive value but may increase downstream testing without reducing cost. Exercise stress testing provides diagnostic and prognostic information, with enhanced accuracy when combined with echocardiography or nuclear imaging. Cardiac catheterization remains the gold standard for coronary assessment but does not exclude vasospasm-related events.
Prehospital and Initial ED Management
Prehospital ECG monitoring improves early detection of ACS. In the emergency department, continuous cardiac monitoring and pulse oximetry are standard. Further management depends on risk stratification and test results.
Diagnostic Strategy in the ED
Patients with concerning history should undergo ECG and initial troponin testing. Abnormal findings warrant admission and cardiology consultation. Persistent symptoms or evolving ECG changes necessitate repeat testing or advanced imaging. Low- to moderate-risk patients may undergo stress testing, either during observation or as an outpatient within 72 hours if reliable follow-up exists. Abnormal ancillary testing requires admission or specialty consultation.
Disposition Planning
Admission is indicated for patients with abnormal ECGs, positive biomarkers, concerning imaging, or unavailable observation resources. Observation units may be used for serial testing when diagnosis is uncertain. Discharge is appropriate for patients with noncardiac histories, normal ECGs, and negative cardiac testing.
Follow-Up Considerations
Abnormal stress tests require close cardiology follow-up. Patients discharged with undifferentiated chest pain should have timely outpatient evaluation if inpatient testing is deferred.
Clinical Insights and Cautions
A normal ECG or troponin does not exclude coronary artery disease. Serial ECGs and additional leads increase diagnostic sensitivity. Most emergency patients with undifferentiated chest pain require some form of additional cardiac testing to safely exclude ACS.
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