Right ventricular hypertrophy and biatrial overload
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Right ventricular hypertrophy is evident in this ECG as right axis deviation (prominent S waves in lead I) and tall R waves in lead V1. Left atrial overload is manifested as broad, M shaped P waves in lead II (P mitrale). Sharp initial positive deflection of the P wave in lead V1 is indicative of right atrial overload. All these findings together can occur in severe mitral stenosis with severe pulmonary hypertension.