What does a large P wave mean?

As a medical professional with expertise in cardiology, I can explain the significance of a large P wave in an electrocardiogram (ECG) reading. A large P wave, particularly when it is tall and peaked, can indicate a condition known as right atrial enlargement. This enlargement of the right atrium is often a result of increased pressure in the pulmonary circulation, a condition known as pulmonary hypertension. Pulmonary hypertension can stem from various causes, including chronic respiratory diseases that lead to cor pulmonale, which is right-sided heart failure due to lung problems. In an ECG, the P wave represents the electrical activity of the atria during atrial depolarization, which is the process that initiates the contraction of the atria to push blood into the ventricles. When the right atrium is enlarged, the P wave can become distorted, appearing taller and more pointed, which is sometimes referred to as P pulmonale. It's important to note that while a large P wave can be a sign of right atrial enlargement, it is not a definitive diagnostic tool on its own. Other diagnostic methods and a comprehensive patient history are necessary to confirm the diagnosis.

The presence of tall, peaked P waves in lead II is a sign of right atrial enlargement, usually due to pulmonary hypertension (e.g. cor pulmonale from chronic respiratory disease). Peaked P waves (P pulmonale) due to right atrial enlargement.