What is the ECG (electrocardiogram) criteria for significant ST (stenosis threshold) depression indicating ischemia?

ECG Criteria for Ischemic ST Depression

The standard criterion for significant ST depression indicating myocardial ischemia is horizontal or downsloping ST segment depression of ≥0.1 mV (1 mm) for 80 ms after the J point in two or more contiguous leads. 1

Key Diagnostic Criteria

• New horizontal or down-sloping ST depression ≥0.05 mV (0.5 mm) in two contiguous leads indicates myocardial ischemia 1
• More severe ST depression (≥0.2 mV or 2 mm) indicates higher risk and more extensive coronary artery disease 1
• Transient ST-segment changes (≥0.05 mV) that develop during symptoms and resolve when asymptomatic strongly suggest acute ischemia 1
• The magnitude of ST depression correlates with risk - greater depression indicates worse prognosis and higher likelihood of multivessel disease 1
• ST depression appearing at lower workloads during exercise testing suggests more severe coronary artery disease 1

Variations in ST Depression Criteria by Patient Demographics

• For men ≥40 years: ST depression ≥0.2 mV is significant 1
• For men <40 years: ST depression ≥0.25 mV is significant 1
• For women: ST depression ≥0.15 mV is significant 1
• Downsloping ST depression is more specific for ischemia than horizontal or upsloping patterns 1

Special Considerations

• ST depression in leads V1-V3 may indicate posterior wall ischemia (especially when terminal T wave is positive) 1
• The presence of ST depression in multiple leads correlates with more extensive coronary artery disease 1
• Duration of ST depression in the recovery phase after exercise correlates with severity of coronary artery disease 1
• ST depression must be distinguished from non-ischemic causes such as LV hypertrophy, bundle branch block, electrolyte abnormalities, and certain medications 1

Interpretation Pitfalls

• Upsloping ST depression is generally considered an "equivocal" response and less specific for ischemia 1
• Pre-existing ST depression requires assessment of additional depression during stress/symptoms 1
• When J point is elevated at rest (early repolarization), measure ST depression from the P-Q junction, not from the elevated J point 1
• ST depression pattern alone cannot reliably predict the specific coronary artery involved 2
• False positives can occur with LV hypertrophy, cardiomyopathies, electrolyte abnormalities, and certain medications 1

Risk Stratification Based on ECG Changes

• High-risk findings requiring immediate intervention include ST depression >2 mm in multiple leads 3
• ST depression with accompanying symptoms (chest pain, dyspnea) indicates higher risk 3
• Persistent or worsening ST changes during recovery phase indicate higher risk 1, 3
• The presence of both ST elevation and depression in the same test may indicate multivessel disease 1

For accurate diagnosis, always compare the current ECG with previous tracings when available and consider the clinical context alongside the ECG findings 1.