In acute left atrial overload, the P wave duration is normal, but there is accentuated P wave negativity in lead V₁. This pattern is seen with conditions that lead to left atrial overload, such as hypertension, aortic valve, and mitral valve disease. 

It may also be seen in the acute stage of myocardial infarction, which normalizes after a few days. An acute left atrial overload pattern may also be due to incorrect placement of leads V₁ and V₂.