The P wave in lead I is positive but of low amplitude. It is in tall and peaked and of almost equal amplitude in leads II, III and aVF. It is directed almost directly inferiorly with an axis of +85 degrees. This type of P wave is characteristic that seen in patients with COPD and is referred to as āP Pulmonaleā The initial component of the QRS complex, with the very small R wave in lead I and the taller R waves in leads II, III and aVF is directed inferiorly with about the same axis as the P wave. It is labelled 1 on the tri-axial figure above the ECG.
The terminal component, with the S wave in all limb leads except aVR is directed superiorly and to the right with an axis (labelled 3) of +210 degrees. The main QRS vector, shown with the arrow labelled 2, has an axis of +135. The vector loop is located almost entirely to the right and is quite circular