The abnormal increase in mass of the right atrium corresponds to a longer activation time. The characteristics of P pulmonale are: 

• An increase in the positive amplitude of the P wave by more than 2.5 mm in leads II, III, and aVF and in V₁ and V₂ at times.
• An increased negative amplitude in aVL by > 2.5 mm.

12-Lead ECG Representing Tall P Waves in Leads II, III, and aVF

Pathologic P pulmonale is rare and found in patients with chronic obstructive pulmonary disease. It can also be a normal variant when P pulmonale is seen in lead II in young asthenic patients or patients with elevated sympathetic tone.