The QRS axis is the most important to determine. However, the P wave or T wave axis can also be measured. To determine the QRS axis, the limb leads (not the precordial leads) need to be examined.

However, the amplitude of the P wave is exaggerated due to the close proximity of the hypertrophied right atrial myocardium to the SA node. This is referred to as p-pulmonale since lung disease ...