he ECG has three parts : the P wave, QRS complex and T wave. The P wave is associated with atrial activation (depolarization), QRS complex is related to ventricular activation (depolarization), and T wave is associated with ventricular recovery (repolarization) phase.
In case of Left atrial enlargement, the P wave shows notched pattern. It looks like two P wave (see the following diagram).
The following diagram shows left atrial enlargement and the pattern of ECG associated with it.
So, I think two P waves with normal QRS complex and T wave is caused by Left atrial enlargement.