A 73-year-old man enters the ICU with chest pain and an irregular pulse. The patient has a long history of coronary artery disease, with a myocardial infarction 10 years ago and coronary artery bypass graft surgery performed 7 years ago. He is known to have a left bundle-branch block on his ECG since his coronary artery bypass graft surgery. In the past 7 years, he has been asymptomatic. He has been taking aspirin for years.
This morning he awoke with substernal chest pressure that lasted < 10 min. Although the pain was similar to that of his myocardial infarction, he graded it only 3 on a scale of 10 in intensity. The patient came to the emergency department, where he was pain free. Physical examination revealed a pulse of 70 beats/min and irregular, and a BP of 130/80 mm Hg. The rest of his physical examination was normal. His ECG is shown (Fig 1
). Blood is drawn for laboratory tests, and he is transferred to the ICU. Initial management of this patient should include which of the following?