The most common ECG finding in the setting of a pulmonary embolism is sinus tachycardia. However, the “S1Q3T3” pattern of acute cor pulmonale is classic; this is termed the McGinn-White Sign.

Atrial fibrillation occurs when action potentials fire very rapidly within the pulmonary veins or atrium ... P waves will not be seen on the ECG in patients with atrial fibrillation.