What is the management approach for patients presenting with chest pain and abnormal ECG (electrocardiogram) findings?

Management of Chest Pain with Abnormal ECG Findings

Obtain and interpret an ECG within 10 minutes of patient arrival, and if ST-elevation is present, immediately activate STEMI protocols for emergent reperfusion therapy; if ST-depression or T-wave inversions are present, manage as NSTE-ACS with urgent cardiology consultation and serial troponin measurements. 1

Immediate ECG-Directed Management Algorithm

Critical ECG Findings Requiring Immediate Action

ST-Elevation Myocardial Infarction (STEMI)

• Follow STEMI guidelines immediately when ST-elevation is identified on the initial ECG 1
• Activate catheterization laboratory for primary percutaneous coronary intervention (PCI) if deliverable within 60-120 minutes, or administer fibrinolysis if PCI is not available 2
• Transfer by emergency medical services (EMS) is strongly recommended because prehospital ECG acquisition facilitates reperfusion, trained personnel can treat arrhythmias and implement defibrillation en route, and travel time to the ED is shorter 1

ST-Depression or New T-Wave Inversions

• Manage according to NSTE-ACS guidelines when ST-depression or new T-wave inversions are present 1
• Initiate antiplatelet therapy (aspirin 250-500 mg immediately if no contraindications), anticoagulation with heparin or low-molecular-weight heparin, and cardiac monitoring with defibrillator readily available 3, 4
• Measure cardiac troponin (cTn) as soon as possible after ED presentation, with high-sensitivity troponin preferred for rapid detection 5, 6

Diffuse ST-Elevation

• Consider pericarditis and manage accordingly rather than activating STEMI protocols 1

New Arrhythmias

• Follow arrhythmia-specific guidelines 1

Management of Nondiagnostic or Normal ECG

Critical Pitfall: Normal ECG Does Not Exclude ACS

A normal or nondiagnostic ECG occurs in 30-40% of patients with acute myocardial infarction, and up to 6% of patients with evolving ACS are discharged from the ED with a normal ECG 1, 6. This represents a major source of missed diagnoses and adverse outcomes.

Serial ECG Protocol

• Perform serial ECGs to detect potential ischemic changes, especially when clinical suspicion of ACS is high, symptoms are persistent, or the clinical condition deteriorates 1
• Repeat ECGs every 15-30 minutes during the first hour if symptoms persist or recur, as ischemic changes may evolve over time 3, 6
• Compare with previous ECGs if available, as left ventricular hypertrophy, bundle branch blocks, and ventricular pacing may mask signs of ischemia or injury 1
• Decision-making should not be based solely on a single normal or nondiagnostic ECG 1, 5

Supplemental ECG Leads

• In patients with intermediate-to-high clinical suspicion for ACS and nondiagnostic initial ECG, obtain supplemental electrocardiographic leads V7 to V9 to rule out posterior MI 1
• A normal ECG may be associated with left circumflex or right coronary artery occlusions and posterior wall ischemia, which is often "electrically silent" 1

Essential Adjunctive Testing

Cardiac Troponin Measurements

• Measure cardiac troponin as the most sensitive test for diagnosing acute myocardial injury, in conjunction with history, examination, and ECG 1
• Repeat troponin at 6-12 hours from symptom onset (not from presentation time) to detect myocardial injury 3, 6
• A single troponin measurement drawn less than 6 hours from symptom onset may miss myocardial injury and should not be used to exclude ACS 3, 6
• Serial troponin measurements are necessary to identify abnormal values and rising/falling patterns 5

Chest Radiography

• Obtain a chest radiograph to evaluate for other potential cardiac, pulmonary, and thoracic causes of symptoms, including aortic dissection (widened mediastinum), heart failure (pulmonary congestion), and pneumothorax 1, 5
• This should not delay urgent revascularization if indicated 1

Risk Stratification and Disposition

High-Risk Features Requiring Immediate Invasive Strategy

• Persistent or recurrent ischemic chest pain despite medical therapy 3, 6
• Dynamic ECG changes on serial testing 3, 6
• Positive second troponin measurement or rising pattern 3, 6
• Hemodynamic instability 3, 6
• Life-threatening arrhythmias 6
• Diabetes mellitus 5

Consider invasive coronary angiography for high-risk patients 5

Intermediate-Risk Patients

• Perform anatomic or functional testing, such as coronary CT angiography 5

Low-Risk Criteria Allowing Discharge

• No recurrent chest pain after 6-12 hours of observation 6
• Normal or unchanged ECG on serial testing 6
• Two negative troponin measurements 6
• No high-risk features present 6

Consider deferring testing or using low-radiation options like ECG or coronary artery calcium scan for low-risk patients 5

Critical Pitfalls to Avoid

• Never delay transfer to the ED for troponin testing from office settings, as this worsens outcomes 1, 3
• Do not rely on a single normal ECG to exclude ACS when clinical suspicion remains high 5, 3
• Do not discharge patients based on a single troponin drawn less than 6 hours from symptom onset 3, 6
• If an ECG cannot be obtained in the office setting within 10 minutes, initiate immediate transfer to the ED by EMS 1
• Do not start thrombolytics without clear ST-elevation or new left bundle branch block on ECG, as this causes harm in non-STEMI patients 6
• Creatine kinase MB isoenzyme and myoglobin are not useful for diagnosis of acute myocardial injury when troponin is available 5

Alternative Diagnoses to Consider

When cardiac causes are excluded by serial ECGs and troponins, evaluate for:

• Aortic dissection 6
• Pulmonary embolism 6
• Pericarditis 1, 6
• Pneumothorax 6
• Esophageal disorders 6
• Myocarditis, arrhythmia, electrolyte abnormalities, hypertrophic cardiomyopathy, pulmonary hypertension 1