This 65-year-old man is seen in the cardiac clinic for a routine follow-up visit. He had a myocardial infarction two years earlier, but has been free of angina with moderate exertion. Lately, he reports feeling more easily fatigued:

• Atrial flutter with 4:1 conduction
• Left axis deviation
• Left bundle branch block

Previously this patient had been in sinus rhythm, with a left bundle branch block pattern since the time of his myocardial infarction. The flutter waves are negative in lead I suggesting a left atrial flutter source.