From the Guidelines
STEMI equivalents include new or presumably new left bundle branch block (LBBB), ST depression in ≥2 precordial leads (V1–V4) indicating transmural posterior injury, and multilead ST depression with coexistent ST elevation in lead aVR, which are indicative of acute coronary occlusion requiring immediate reperfusion therapy. These equivalents are crucial to identify as they may not meet traditional ST-elevation myocardial infarction criteria but still require urgent treatment to reduce morbidity and mortality 1.
Key Points to Consider
- New or presumably new LBBB is considered a STEMI equivalent, although it may interfere with ST-elevation analysis 1.
- Baseline ECG abnormalities other than LBBB, such as paced rhythm, LV hypertrophy, or Brugada syndrome, may obscure interpretation 1.
- Transthoracic echocardiography may provide evidence of focal wall motion abnormalities and facilitate triage in patients with ECG findings that are difficult to interpret 1.
- Cardiac troponin is the preferred biomarker for diagnosis of MI 1.
Clinical Implications
- Recognition of STEMI equivalents is crucial because delays in reperfusion therapy significantly increase morbidity and mortality.
- Treatment includes immediate administration of aspirin, consideration of P2Y12 inhibitors, anticoagulation with unfractionated heparin, and rapid transfer for primary percutaneous coronary intervention.
- The pathophysiology involves complete or near-complete coronary artery occlusion causing myocardial ischemia that manifests with these specific ECG patterns rather than classic ST elevations.
From the Research
STEMI Equivalents
STEMI equivalents refer to electrocardiogram (ECG) patterns that indicate a high likelihood of acute coronary occlusion, similar to ST-segment elevation myocardial infarction (STEMI). These patterns require immediate attention and aggressive intervention, just like STEMI.
Examples of STEMI Equivalents
- Left bundle branch block (LBBB) with concordant ST-segment elevation 2, 3
- De Winter/ST/T complex 4
- ST-segment elevation in lead aVR 4, 5
- Wellens' phenomenon 4
- Posterior wall myocardial infarction 4
- Pathologic ST changes in the presence of LBBB and pacemakers 4
- Hyperacute T-waves 5
- Subtle ST-segment elevations 5
- ST-segment elevation in leads aVR/V1 with concomitant ST-segment depression in ≥8 other leads 5
- High R-peak with positive T-waves combined with horizontal ST-segment depression in leads V1/V2 5
Diagnostic Criteria
The Sgarbossa rule is a diagnostic tool used to identify STEMI equivalents in patients with LBBB. The rule has been modified to improve its diagnostic utility, replacing the third component with an ST-elevation to S-wave ratio (ST/S ratio) of less than -0.25 6. This revised rule has been shown to have better diagnostic utility for STEMI equivalents, with a sensitivity of 91% and specificity of 90% 6.