How Slow Can You Go?

A 66-year-old man presents to the Emergency Department (ED) with chest pain and shortness of breath that started several hours ago as he was cleaning his porch. His chest pain is dull in quality and radiates to his neck and arms, and when asked to rate the severity of the pain, he indicates a 5 in a range from 1 to 10 (with 10 being the worst). The chest pain is not associated with diaphoresis, nausea, or vomiting. The patient also had exertional weakness for 4 days. He denies having dizziness, lightheadedness, or loss of consciousness.

The patient underwent a 3-vessel coronary artery bypass 8 years ago. Since then, he has had stable angina that occurs approximately once a month. His medical history is also clinically significant for hyperlipidemia, hypertension, and poorly controlled insulin-dependent diabetes mellitus. His medication regimen includes hydrochlorothiazide, insulin, isosorbide dinitrate, simvastatin, aspirin, and sublingual nitroglycerin as needed. The patient smokes 2 packs of cigarettes per day. The review of systems yields unremarkable findings.

The patient is afebrile but appears uncomfortable. The cardiovascular examination reveals bradycardia. His heart rate is 39 bpm and regular, his blood pressure is 130/53 mm Hg, and his respiratory rate is 18 breaths per minute. His first and second heart sounds are normal. No murmur or gallop is present. Except for evidence of his previous surgery, his other physical findings are normal.

The patient’s laboratory results are normal except for mildly elevated troponin I levels. An ECG is obtained (see Image 1).

What is the diagnosis?

What is the diagnosis?
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Identify the P waves.