Reading the ST Segment First
ST-segment shape splits acute coronary syndromes into two urgent tracks.
- ST elevation: STEMI ECG sign (≥1mm, contiguous leads)
- ST depression: NSTEMI ECG sign (or normal / T inversion)
- Troponin +: Shared marker (both are troponin-positive)
- 12-lead ECG: First test (within 10 minutes of arrival)
Why the ECG decides the pathway
Placeholder: ST elevation implies complete occlusion needing emergency reperfusion.
Placeholder: ECG pattern, not symptoms alone, drives the treatment clock.
Full-Thickness Occlusion
Complete coronary occlusion damages the entire wall thickness.
- Complete: Occlusion type (total vessel occlusion)
- 3 of 3: Wall layers hit (epi + myo + endocardium)
- ST↑ + Q wave: ECG hallmark (evolving pattern)
- High: Risk if delayed (myocardium at risk grows)
Transmural damage mechanism
Placeholder: full-thickness ischemia elevates the ST segment on ECG.
Placeholder: time lost equals muscle lost in transmural infarction.
Partial-Thickness Ischemia
Subendocardium is most vulnerable, so injury stays partial-thickness.
- Partial/subtotal: Occlusion type (or transient occlusion)
- Inner 1 of 3: Wall layers hit (subendocardial band)
- ST↓ / T inversion: ECG hallmark (or normal ECG)
- Troponin: Diagnosis needs (ECG alone insufficient)
Subendocardial vulnerability
Placeholder: inner wall gets least collateral flow, so it ischemes first.
Placeholder: normal ECG never excludes NSTEMI without troponin.
STEMI: Door-to-Balloon Race
STEMI triggers immediate cath lab activation, bypassing risk scoring.
- ≤90 min: Goal (door-to-balloon time)
- Activate cath lab: Action (pre-hospital if possible)
- Primary PCI: Strategy (or fibrinolysis if delayed)
- ECG alone: Decision basis (no waiting for troponin)
Emergent reperfusion logic
Placeholder: every 30-minute delay increases mortality risk.
Placeholder: cath lab activation happens on ECG, not lab results.
NSTEMI: Timed, Risk-Based Angiography
NSTEMI care uses risk scores to time invasive strategy, not rush it.
- GRACE/TIMI score: Tool (risk stratification)
- <24 h: High-risk timing (early invasive strategy)
- 24–72 h: Lower-risk timing (or ischemia-guided)
- Antiplatelet/anticoag: Medical therapy (started immediately)
Why NSTEMI is not rushed the same way
Placeholder: risk score guides whether angiography is urgent or elective.
Placeholder: stability allows risk-based timing instead of emergent PCI.