Axis-deviation

Left axis deviation (LAD)

• Definition: axis beyond –30° (S >R in lead II)

• Etiologies: LVH, LBBB, inferior MI, WPW

• Left anterior fascicular block (LAFB): LAD (–45 to –90°) and qR in aVL and QRS <120 msec and no other cause of LAD (eg, IMI)

Right axis deviation (RAD)

• Definition: axis beyond +90° (S >R in lead I)

• Etiologies: RVH, PE, COPD (usually not >+110°), septal defects, lateral MI, WPW

• Left posterior fascicular block (LPFB): RAD (90–180°) and rS in I & aVL and qR in III & aVF and QRS <120 msec and no other cause of RAD