Changing P waves after mitral valve replacement.

A 55-year-old man is convalescing from mitral valve replacement five days earlier. He had severe calcific mitral stenosis and moderately severe hypertension, with repeated attacks of acute pulmonary edema. He had always been in normal sinus rhythm, except for a single episode of atrial fibrillation associated with one of his episodes of acute pulmonary edema. He had been taking digoxin (0.25 mg daily) but this was stopped the day before the operation. The cardiac rhythm has been mostly regular since the operation, but occasional irregularities have been noted. An ECG on the fifth postoperative day is shown.