Arrhythmias USMLE Step 1 Practice Question
A 79-year-old man takes high-dose beta blockers for coronary disease. He presents with dizziness. ECG shows a heart rate of 42 per minute with narrow QRS complexes and no preceding P waves; inverted P waves are seen after some QRS complexes. Which of the following is the most likely source of this rhythm?
Answer choices
- ASinoatrial node
- BVentricular myocardium
- CAccessory pathway
- DAV junctionCorrect answer
- EAtrial ectopic focus
- FPurkinje fibers
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