What are the causes of ST elevation?

Causes of ST Elevation

ST-segment elevation can have multiple causes including myocardial infarction, pericarditis, coronary spasm, old STEMI with aneurysm formation, conduction abnormalities, and early repolarization. 1 Understanding these various etiologies is crucial for proper diagnosis and management.

Primary Cardiac Causes

1. Acute Coronary Occlusion (STEMI)

• Most common and serious cause requiring immediate intervention
• Results from:
  • Thrombus formation on disrupted atherosclerotic plaque (most common) 1
  • Coronary artery occlusion due to plaque rupture, ulceration, fissure, or erosion 1
  • Complete thrombotic occlusion of an epicardial coronary vessel 2

2. Coronary Vasospasm

• Intense focal spasm of an epicardial coronary artery segment (Prinzmetal's angina) 1
• Can occur with or without underlying atherosclerotic disease
• May be triggered by:
  • Hypercontractility of vascular smooth muscle
  • Endothelial dysfunction
  • Cocaine use (presumed mechanism for cocaine-induced ST elevation) 1

3. Pericarditis

• Inflammation of the pericardium causing diffuse ST elevation
• Usually concave upward ST elevation in multiple leads
• Often accompanied by PR depression 1

4. Previous Myocardial Infarction with Aneurysm Formation

• Persistent ST elevation after completed infarction
• Represents ventricular wall motion abnormality and aneurysm formation 1
• Occurs in <5% of patients after STEMI, more frequent with anterior infarctions 1

Conduction and Repolarization Abnormalities

1. Early Repolarization

• Normal variant, especially in young males
• Characterized by ST elevation at J-point with concave upward appearance
• Usually most prominent in precordial leads 1

2. Left Bundle Branch Block (LBBB)

• Can interfere with ST-segment analysis
• New or presumably new LBBB was historically considered a STEMI equivalent
• However, isolated LBBB should not be considered diagnostic of acute MI 1

3. Right Bundle Branch Block (RBBB)

• When associated with STEMI, indicates more extensive myocardial involvement
• Particularly ominous when seen with anterior wall MI as it suggests proximal LAD occlusion 3

4. Left Ventricular Hypertrophy

• Can cause secondary ST-T changes that may mimic or mask STEMI 1

Other Cardiac Causes

1. Brugada Syndrome

• Genetic disorder affecting cardiac sodium channels
• Characteristic ST elevation in right precordial leads (V1-V3) 1

2. Takotsubo Cardiomyopathy (Stress-Induced)

• Transient left ventricular dysfunction following acute emotional or physical stress
• ECG changes can mimic STEMI

3. Myocarditis

• Inflammation of the myocardium that can produce ST elevation
• May be difficult to distinguish from STEMI without additional testing

Non-Cardiac or Secondary Causes

1. Secondary Unstable Angina

• Conditions that increase myocardial oxygen demand or decrease supply:
  • Fever, tachycardia, thyrotoxicosis (increased demand)
  • Hypotension (decreased supply)
  • Anemia, hypoxemia (decreased oxygen content) 1

2. Electrolyte Abnormalities

• Hyperkalemia can cause ST elevation

3. Lead Misplacement

• Incorrect ECG lead placement can result in apparent ST elevation

Special Considerations

aVR ST Elevation

• ST elevation in lead aVR with multilead ST depression was previously thought to indicate left main or proximal LAD occlusion
• Recent research shows only 10% of such patients have acute thrombotic coronary occlusion 4
• Associated with high in-hospital mortality (31%) compared to other STEMI patterns 4

Posterior MI

• May present with ST depression in anterior leads (V1-V4) rather than ST elevation
• Should be considered a STEMI equivalent when clinical context is appropriate 1

Clinical Implications

When evaluating ST elevation, it's important to consider the clinical context. In patients with appropriate chest pain syndrome, ST elevation should be presumed to represent coronary occlusion until proven otherwise, especially in resource-limited settings 1. Prompt recognition and appropriate triage are essential as "time is muscle" in true STEMI cases.

The diagnosis of STEMI requires both:

1. ST elevation on ECG (≥2 mm in men or ≥1.5 mm in women in leads V2-V3, and/or ≥1 mm in other contiguous leads) 1
2. Clinical context consistent with myocardial ischemia 1

Failure to recognize non-ischemic causes of ST elevation may lead to unnecessary cardiac catheterization, while missing true STEMI can result in delayed reperfusion and increased mortality.