Intraventricular Arachnoid Cyst: (Left) T1-weighted axial MRI; (Right) T2-weighted axial MRI. Note the large cyst in the atrium of the right lateral ventricle. The cyst contains fluid, thus it is dark ...

The ECG criteria for diagnosing right atrial enlargement (RAE) are as follows: The P wave amplitude in lead II > 2.5 mm, or; The upward deflection of the P wave in lead V1 > 1.5 mm in amplitude.