What is a pulmonary P wave seen in?

Pulmonary P wave, also known as mitral P wave, primarily reflects the blood flow velocity and congestion status in the pulmonary artery. Therefore, the presence of a pulmonary P wave usually indicates chronic lung inflammation, increased pulmonary arterial pressure, or pulmonary valve stenosis. The main cause of pulmonary P wave is cor pulmonale (pulmonary heart disease). However, primary cardiac conditions such as tricuspid stenosis or tricuspid regurgitation may also lead to the appearance of a pulmonary P wave.

1. Pulmonary Heart Disease

When pulmonary diseases such as interstitial lung disease or primary pulmonary hypertension lead to pulmonary hypertension, they increase the afterload on the right atrium. Over time, this results in the development of a pulmonary P wave. In this condition, the depolarization time is prolonged and often overlaps with the slightly delayed depolarization of the left atrium. As a result, the total atrial depolarization duration does not lengthen, but instead manifests as an increased amplitude of atrial depolarization—specifically, a P wave amplitude ≥ 0.25 mV—known as a pulmonary P wave. Thus, a pulmonary P wave typically suggests the possible presence of underlying lung disease.

2. Primary Heart Disease

In cases of primary heart diseases such as tricuspid stenosis or tricuspid regurgitation, a pulmonary P wave may also appear on the electrocardiogram (ECG), although it is usually not accompanied by right atrial hypertrophy.

When a pulmonary P wave is detected on ECG, further evaluations should be performed, including BNP testing, echocardiography, chest CT, and pulmonary function tests, to determine the underlying cause and guide appropriate symptomatic and etiology-based treatment.