ECG Basics and Fundamentals: right axis deviation differential and ST segment elevation in rightward leads

ECG Weekly Workout with Dr. Amal Mattu


A 48-year-old woman presents to the ED with chest pain and near syncope. The following ECG is obtained:

Before watching this week’s video, ask yourself these questions:

  1. What ECG abnormalities do you notice?
  2. What is the axis?
  3. What is the most likely diagnosis?
Big thanks to Dr. Doug Sward for sharing his case this week!
Key Teaching Points

Differential diagnoses for rightward axis

  • Acute pulmonary HTN – Acute (PE) & chronic lung disease (COPD)
  • Hyperkalemia
  • Na+channel blocker toxicity
  • Ventricular ectopy
  • Right ventricular hypertrophy
  • Left posterior fascicular block
  • Old lateral MI (from Q-waves in lead I)
  • Ventricular ectopy
  • Lead misplacement / Dextrocardia
  • Normal variant in young kids & thin adults with horizontally positioned hearts

Take-home Points:

  • PE and hyperkalemia can cause ST segment elevation
  • Especially in the rightward leads (V1, aVR, ± V2, III)