What is the management approach for a patient presenting with chest pain or shortness of breath and an inconclusive electrocardiogram (ECG)?

Management of Chest Pain or Shortness of Breath with Inconclusive ECG

Obtain an ECG within 10 minutes and measure cardiac troponin immediately, then perform serial troponin measurements at 6-12 hours from symptom onset with repeat ECGs if symptoms persist—do not start lidocaine infusion or thrombolytics without clear STEMI criteria, and reserve angiography for high-risk features that develop during observation. 1, 2, 3

Immediate Actions Upon Presentation

• Perform a 12-lead ECG within 10 minutes of arrival to any medical facility, regardless of setting 1, 2
• Measure cardiac troponin (cTn) as soon as possible after ED presentation; high-sensitivity troponin is preferred for rapid detection 1, 2
• Administer oxygen, aspirin, and nitrates for acute ischemic chest pain while awaiting diagnostic results 4
• Provide opioid analgesia if chest pain is severe 4

Critical ECG Interpretation

• If ST-segment elevation is present: Manage as STEMI with immediate reperfusion therapy (thrombolytics or primary PCI depending on transfer time and facility capabilities) 1, 2, 4
• If ST-segment depression or new T-wave inversions: Manage as NSTE-ACS with aspirin, beta-blockers, nitrates, and low-molecular-weight heparin 1, 2, 4
• If ECG is normal or nondiagnostic: This occurs in 30-40% of patients with acute MI and does NOT exclude ACS 1

Serial Testing Protocol for Inconclusive Initial Results

When the initial ECG and troponin are nondiagnostic:

• Repeat troponin at 6-12 hours from symptom onset (not from presentation time)—this is the critical window for detecting myocardial injury 2, 3
• Perform serial ECGs every 15-30 minutes during the first hour if symptoms persist or recur 1, 3
• Consider supplemental ECG leads V7-V9 if posterior MI is suspected despite nondiagnostic standard 12-lead 3
• Consider right-sided leads V3R-V4R if inferior changes suggest possible right ventricular involvement 1

Risk Stratification During Observation

High-risk features requiring immediate angiography: 2, 3

• Persistent or recurrent ischemic chest pain despite medical therapy
• Dynamic ECG changes (including pseudonormalization of T-waves)
• Positive second troponin measurement or rising pattern
• Hemodynamic instability (hypotension, pulmonary edema, new S3 gallop, new mitral regurgitation murmur)
• Life-threatening arrhythmias (ventricular tachycardia, ventricular fibrillation)
• Elevated troponin levels with diabetes mellitus

Low-risk criteria allowing discharge with outpatient testing: 2, 3

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

Medical Management During Observation

For patients without clear STEMI but with suspected ACS:

• Aspirin 75-150 mg daily 4
• Beta-blockers (if no contraindications) 4
• Nitrates for persistent or recurrent chest pain 5, 4
• Low-molecular-weight heparin during observation period 1, 4
• Consider adding clopidogrel if proceeding to stress testing after negative serial workup 3

Critical Pitfalls to Avoid

• Never rely on a single troponin measurement if drawn less than 6 hours from symptom onset—myocardial injury may not yet be detectable 3
• Do not start thrombolytics without clear ST-elevation or new left bundle branch block on ECG—this causes harm in non-STEMI patients 1, 4
• Do not start lidocaine infusion empirically—it is not indicated for chest pain evaluation and is reserved for specific ventricular arrhythmias in the setting of acute MI 1
• Do not dismiss subtle ECG changes, particularly pseudonormalization of T-waves, which represents active ischemia 3
• Avoid delayed transfer to ED for troponin testing from office settings—this worsens outcomes 1, 2
• Do not discharge patients with a single normal ECG when clinical suspicion remains high—5-40% of patients with normal initial ECG develop acute MI 1

Disposition Algorithm

Proceed to coronary angiography if: 2, 3

• Any high-risk feature develops during observation
• STEMI criteria met on ECG
• NSTE-ACS with elevated troponin and high-risk clinical features

Perform stress testing (before discharge or outpatient) if: 2, 3

• Serial troponins negative at 6-12 hours
• No recurrent symptoms
• ECG remains normal or unchanged
• No high-risk features present

Consider discharge without objective testing if: 2, 6

• Low-risk by validated risk scores
• Negative serial troponins and ECGs
• No cardiac risk factors, previous MI, or coronary disease
• Age and sex appropriate for low-risk category

Alternative Diagnoses to Consider

When cardiac causes are excluded, evaluate for: 1

• Aortic dissection: Back pain, pulse differential ≥15 mmHg between arms, aortic regurgitation murmur—requires CT angiography
• Pulmonary embolism: Tachycardia with dyspnea in >90% of cases, pleuritic pain—consider D-dimer and CT pulmonary angiography
• Pericarditis: Pleuritic pain worse when supine, friction rub, fever
• Pneumothorax: Unilateral absent breath sounds, dyspnea with inspiration
• Esophageal disorders: Epigastric tenderness, relation to meals