EKG
Pericarditis vs PE vs STEMI mimics
EKG

Pericarditis vs PE vs STEMI mimics

Diffuse ST elevation, PR depression, S1Q3T3 — what's not a STEMI.

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◆Acute pericarditis

  • •DIFFUSE concave ST elevation (all leads except aVR + V1)
  • •PR DEPRESSION in same leads (PR elevation in aVR)
  • •No reciprocal changes (vs STEMI)
  • •Often follows viral URI; pleuritic chest pain worse supine, better leaning forward; friction rub
  • •Treat: NSAIDs (or aspirin if post-MI) + colchicine; steroids only if refractory or autoimmune

◆Pulmonary embolism

  • •Most common EKG finding: SINUS TACHYCARDIA
  • •Classic but UNcommon: S1Q3T3 — deep S in I, Q wave in III, inverted T in III (RV strain)
  • •T-wave inversions V1–V4 (anterior); new RBBB; right axis deviation
  • •Diagnose with CT-PA (or V/Q if contrast contraindicated); D-dimer for low-pretest probability
  • •Treat: anticoagulation (DOAC if hemodynamically stable); tPA if massive PE with shock

◆STEMI mimics to know

  • •Benign early repolarization: J-point notch, concave ST elevation in V2–V5, no reciprocal changes
  • •LBBB: discordant ST/T (opposite QRS direction) — use Sgarbossa criteria for STEMI in LBBB
  • •LV aneurysm: persistent ST elevation weeks after MI
  • •Brugada: coved ST elevation V1–V3 + RBBB-like pattern — channelopathy, risk of sudden death
  • •Takotsubo cardiomyopathy: ST elevation that doesn't fit a vascular territory, apical ballooning, post-stressor

ST-elevation differential

PatternDiagnosis
Localized ST elevation + reciprocal depressionSTEMI
Diffuse concave ST elevation + PR depressionPericarditis
Coved ST V1–V3 + RBBB-likeBrugada
Concave ST V2–V5 + J notchEarly repolarization (benign)
Persistent ST elevation post-MILV aneurysm

High-yield pearls

  • ◆Pericarditis with effusion + Beck's triad (hypotension, JVD, muffled heart sounds) = tamponade → urgent pericardiocentesis
  • ◆Most common EKG finding in PE is sinus tach — don't anchor on S1Q3T3
  • ◆Brugada is autosomal dominant — screen first-degree relatives; ICD if syncope
  • ◆Wellens' (deep biphasic T waves V2–V3) in pain-free patient = critical LAD stenosis
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