This electrocardiogram shows right ventricular hypertrophy and right atrial enlargement. The characteristic features of right ventricular hypertrophy demonstrated here include: the tall R waves in leads V1 through V4, associated with ST-T wave abnormalities in these leads, and right axis deviation, in part reflected by the negative QRS complex in lead I. Right atrial enlargement is reflected by the tall, narrow P waves in leads II and V1, and is commonly seen with right ventricular hypertrophy. The electrocardiographic changes seen here are typically found when there is right ventricular pressure overload.