;Right atrial enlargement is defined as either:
,5 mm in II / III and / or aVF :P >1 ,5 mm in V1.
Right atrial enlargement can result from increased pressure in the pulmonary artery, e.g. after pulmonary embolization. A positive part of the biphasic p-wave in lead V1 larger than the negative part indicates right atrial enlargement. The width of the p wave does not change.