Very slow heart rate!!!!!!!!!!!

[unseennude]

A 63-year-old man presents to the emergency department for an evaluation of new-onset renal failure. The patient's primary care physician referred him after routine laboratory tests demonstrated a blood urea nitrogen (BUN) level of 83 mg/dL (30 mmol/L) and a creatinine of 4.4 mg/dL (389 mmol/L).

The patient reports feeling well without any current symptoms. He denies having chest discomfort, difficulty breathing, or palpitations. He has a history of urinary hesitancy secondary to benign prostatic hypertrophy, but he is voiding as usual. His medical history is also significant for diabetes mellitus, hypertension, and a remote history of syncope.

On physical examination, the patient is afebrile with a heart rate of 71 bpm, a respiratory rate of 16 breaths per minute, and a blood pressure of 160/85 mm Hg. The patient appears well and is in no acute distress. His heart is regular, with a normal S1 and S2 and a III/VI systolic crescendo-decrescendo murmur that is loudest at the left sternal border. No rubs or gallops are appreciated, and he has no jugular venous distention. His lungs are clear bilaterally. His abdomen is soft without any tenderness or masses. He has 1+ peripheral edema of both legs.

A repeat chemistry panel is significant for a normal potassium level of 3.8 mEq/L (3.8 mmol/L), a BUN level of 96 mg/dL (34 mmol/L), and a creatinine level of 4.7 mg/dL (415 μmol/L). After a nephrologist is consulted, the patient is admitted to the hospital for further workup of renal failure and possible dialysis.



Before the patient is transferred and after a few hours in the emergency department, the nurse observes that he is markedly bradycardic. On repeat physical examination, the patient is resting comfortably and alert, with a regular pulse of 36 bpm. His blood pressure is 156/79 mm Hg. His physical findings are otherwise unchanged. An ECG (see Image) is obtained while the nurse places external cardiac pacer pads on the patient and brings resuscitation equipment to the bedside.

What diagnosis does the ECG suggest?
Hint:What is the relationship between the P waves and the QRS complexes?