Putting it together: one dipole, twelve views

All twelve leads are projections of a single cardiac dipole (the VCG) onto different axes, eight measured (I, II, V1–V6) and four derived (III, aVR, aVL, aVF). One heartbeat, twelve viewpoints. Every diagnosis from here on is a deviation from this normal projection.

• Frontal plane: I, II, III, aVR, aVL, aVF (the limb leads).
• Horizontal plane: V1–V6 (the precordial leads).
• One dipole projected many ways, hold this picture as the baseline for Phase 2.