This is an electrocardiogram, a 64 year-old man with a history of coronary artery disease. The patient was taking amiodarone , metoprolol , and Vasotec at the time of this recording. This was a routine recording. The electrocardiogram shows sinus rhythm with a prolonged P wave > 120 milliseconds. The P wave is notched in the inferior leads. This is consistent with a left atrial abnormality. The PR interval is long at 200 milliseconds and is diagnostic of first-degree heart block. The Q waves in the Interior leads suggest an inferior wall infarction .