What amplitude of ST‑segment depression measured 80 ms after the J point is considered significant for myocardial ischemia?

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Last updated: October 20, 2026 • View editorial policy

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ST-Segment Depression Threshold for Myocardial Ischemia

Horizontal or downsloping ST-segment depression ≥0.5 mm (0.05 mV) measured at the J-point in 2 or more contiguous leads is considered significant for myocardial ischemia 1.

Key Measurement Parameters

The measurement should be performed with these specific technical details:

  • Measurement point: At the J-point (junction of QRS complex and ST segment) or 60-80 ms after the J-point
  • Amplitude threshold: ≥0.5 mm (0.05 mV)
  • Morphology: Horizontal or downsloping depression (upsloping is generally equivocal)
  • Lead requirement: Present in 2 or more anatomically contiguous leads
  • Reference baseline: Measured from the P-Q junction (isoelectric line)

Context-Specific Thresholds

Acute Coronary Syndrome (Resting ECG)

The 2022 ACC Expert Consensus 1 and 2012 Universal Definition of MI 2 both specify ≥0.5 mm horizontal or downsloping ST depression in contiguous leads as suggestive of ischemia. The 2009 AHA/ACCF recommendations 3, 4 further clarify that the threshold for abnormal J-point depression is 0.5 mm in leads V2-V3 and 1.0 mm in all other leads.

Exercise Stress Testing

For exercise-induced ischemia, the threshold is higher: ≥1.0 mm (0.1 mV) horizontal or downsloping ST depression measured at 60-80 ms after the J-point 5, 6, 5, 6. This represents the standard criterion that has been validated over decades of use.

Critical Morphology Distinctions

Downsloping ST depression is more specific for ischemia than horizontal depression, and both are far more specific than upsloping depression 5, 6, 5, 6. Upsloping ST depression is generally considered equivocal unless markedly depressed (≥2.0 mm at 80 ms after J-point in highly symptomatic patients) 5.

Special Considerations and Pitfalls

ST depression maximal in leads V1-V4 (rather than V5-V6) has 97% specificity for occlusion MI and often represents posterior wall ischemia from circumflex occlusion—a commonly missed STEMI equivalent 7. This pattern warrants emergent catheterization even without traditional STEMI criteria.

When baseline ST depression exists, measure only the additional ST depression during the acute event or exercise 5. If early repolarization with J-point elevation is present at baseline, only measure ST changes below the P-Q baseline 5.

In the presence of left bundle branch block, concordant ST depression ≥1 mm in leads V1-V3 scores 3 points in the modified Sgarbossa criteria and is highly specific for acute MI 1.

Timing of Measurement

Recent research suggests measuring ST deviation close to the J-point (within 10-20 ms) may optimize diagnostic accuracy 8, 9, though the established standard remains 60-80 ms after the J-point for consistency and to account for heart rate variations 5.

At heart rates >130 bpm, measure at 60 ms rather than 80 ms after the J-point to avoid encroaching on the T wave 5, 6.

Prognostic Implications

The magnitude, number of leads involved, timing of appearance, and duration of ST depression all correlate with severity of coronary disease and prognosis 5, 6, 5, 6. Earlier appearance during exercise (lower workload/rate-pressure product) indicates worse prognosis and higher likelihood of multivessel disease 5, 6, 5, 6.

References

2
Guideline

third universal definition of myocardial infarction.

Journal of the American College of Cardiology, 2012

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