What is the management approach for ischemia detected on electrocardiogram (ECG)?

Management of Ischemia Detected on ECG

When ischemia is detected on ECG, obtain a 12-lead ECG within 10 minutes of first medical contact, initiate continuous cardiac monitoring immediately, administer aspirin 150-325 mg, and determine whether ST-segment elevation criteria are met to guide urgent reperfusion therapy. 1

Immediate Actions at First Medical Contact

• Acquire and interpret a 12-lead ECG within 10 minutes to identify STEMI versus non-ST-elevation acute coronary syndrome (NSTE-ACS) 1
• Initiate continuous ECG monitoring immediately to detect life-threatening arrhythmias requiring prompt defibrillation 1, 2
• Administer aspirin 150-325 mg orally (or 75-250 mg IV) unless contraindicated 1, 2, 3
• Establish intravenous access and prepare for urgent interventions 2
• Provide supplemental oxygen if oxygen saturation <90%, cyanosis, or respiratory distress is present 1

ECG Interpretation and Risk Stratification

STEMI Criteria (Requires Immediate Reperfusion)

• ST-segment elevation ≥1 mm in ≥2 contiguous leads (except V2-V3) 1
• In leads V2-V3: ≥2 mm in men ≥40 years, ≥2.5 mm in men <40 years, ≥1.5 mm in women regardless of age 1
• Obtain posterior leads (V7-V9) when isolated ST-depression ≥0.5 mm occurs in V1-V3, suggesting left circumflex occlusion 1
• Record right precordial leads (V3R, V4R) in inferior MI to identify right ventricular infarction 1

NSTE-ACS Criteria

• Horizontal or downsloping ST-depression ≥0.5 mm in ≥2 contiguous leads 1
• T-wave inversion >1 mm in ≥2 contiguous leads with prominent R wave or R/S ratio >1 1
• Transient ST-segment elevation 1

Critical Pitfall

Many patients with NSTE-ACS have nonspecific ST-T changes or normal ECG—absence of electrocardiographic ischemia does not exclude ACS. 1 If clinical suspicion remains high despite nondiagnostic initial ECG, perform serial ECGs every 15-20 minutes, especially with persistent symptoms or clinical deterioration 1, 4

Immediate Medical Therapy

Antiplatelet Therapy

• Aspirin 150-300 mg loading dose (or 75-250 mg IV), then 75-100 mg daily long-term 1
• Add P2Y12 inhibitor (prasugrel 60 mg loading dose, 10 mg daily; or ticagrelor) in addition to aspirin, maintained for 12 months unless excessive bleeding risk 1

Anti-Ischemic Therapy

• Nitroglycerin sublingual (tablet or spray) for immediate symptom relief, followed by IV administration if pain persists 1, 2
• Beta-blocker: First dose IV if ongoing chest pain, then oral administration (unless contraindicated by severe LV dysfunction, heart failure, bradycardia, or hypotension) 1
• Morphine sulfate IV when symptoms not immediately relieved with nitroglycerin or when acute pulmonary congestion/severe agitation present 1, 2

Anticoagulation

• Heparin (unfractionated or low-molecular-weight) should be initiated 1

Reperfusion Strategy Decision

For STEMI

Immediate EMS transport to PCI-capable hospital for primary PCI is the recommended strategy, with first medical contact-to-device time goal ≤90 minutes. 1, 2

• Early advance notification of receiving PCI-capable hospital by EMS personnel to activate cardiac catheterization team 1
• Primary PCI preferred over fibrinolysis when performed within 120 minutes by experienced team 2

For NSTE-ACS

• Measure high-sensitivity cardiac troponin immediately and obtain results within 60 minutes 1
• Use ESC 0h/1h algorithm with blood sampling at 0 and 1 hour if validated hs-cTn test available 1
• Additional testing at 3 hours if first two measurements inconclusive and clinical condition still suggestive of ACS 1

Continuous Monitoring Requirements

• Admit to monitored unit until NSTEMI established or ruled out 1
• Rhythm monitoring for ≥24 hours or until PCI (whichever first) in low-risk NSTEMI patients 1
• Rhythm monitoring >24 hours in NSTEMI patients at increased risk for cardiac arrhythmias 1
• Bed rest with continuous ECG monitoring for ischemia and arrhythmia detection in patients with ongoing rest pain 1

Special ECG Patterns Requiring Urgent Angiography

Atypical Presentations

• New or presumed new left bundle branch block with clinical suspicion of ongoing ischemia requires prompt reperfusion therapy, preferably emergency angiography with view to primary PCI 1
• Ventricular paced rhythm preventing ST-segment interpretation may require urgent angiography to confirm diagnosis 1
• Isolated posterior MI: ST-depression ≥0.5 mm in V1-V3 with positive terminal T-wave should be managed as STEMI; confirm with ST-elevation ≥0.5 mm in V7-V9 1
• Left main obstruction pattern: ST-depression ≥0.1 mm in ≥8 surface leads coupled with ST-elevation in aVR and/or V1, particularly with hemodynamic compromise 1

Critical Caveat

Ongoing suspicion of myocardial ischemia despite medical therapy is an indication for emergency coronary angiography with view to revascularization, even without diagnostic ST-segment elevation. 1

Serial ECG Monitoring

• Repeat ECG if recurrent symptoms or diagnostic uncertainty 1
• Serial ECGs detect evolving ischemic changes with higher sensitivity (68.1%) than single initial ECG (55.4%) for detecting acute MI 4
• Automated serial 12-lead ECG monitoring every 20 minutes during ED evaluation improves detection of new or evolving injury/ischemia 4

Risk Stratification for Triage

Patients with any sign of ischemia or infarction on initial ECG, plus those with low systolic blood pressure (<110 mmHg), pulmonary rales, or exacerbation of ischemic heart disease require inpatient ECG monitoring for 12-24 hours until acute MI ruled out by negative biomarkers. 1

Additional Diagnostic Testing

• Echocardiography immediately in patients with cardiac arrest or hemodynamic instability of presumed cardiovascular origin 1
• Non-invasive stress test or coronary CT angiography before invasive approach in patients with no recurrent chest pain, normal ECG, and normal troponin but still suspected ACS 1