A 60-year-old man comes to the emergency department because of a 3-day history of intermittent shortness of breath and palpitations. The episodes are unprovoked and occur randomly. The day before, he felt lightheaded while walking and had to sit down abruptly to keep from passing out. He has hypertension. He does not drink alcohol or use any illicit drugs. He has smoked one-half pack of cigarettes daily for 20 years. Current medications include aspirin, metoprolol, lisinopril. He appears well. An ECG obtained in the emergency department is shown in the exhibit. Cell degeneration in which of the following locations is most likely responsible for this patient's current condition?

Question

A 60-year-old man comes to the emergency department because of a 3-day history of intermittent shortness of breath and palpitations. The episodes are unprovoked and occur randomly. The day before, he felt lightheaded while walking and had to sit down abruptly to keep from passing out. He has hypertension. He does not drink alcohol or use any illicit drugs. He has smoked one-half pack of cigarettes daily for 20 years. Current medications include aspirin, metoprolol, lisinopril. He appears well. An ECG obtained in the emergency department is shown in the exhibit.  Cell degeneration in which of the following locations is most likely responsible for this patient's current condition?

Quizplus · Accepted Answer

Eductional Objective: Sick sinus syndrome results from degeneration (usually age-related) of the sinoatrial node, leading to impaired conduction and reduced cardiac output with symptoms of dyspnea, fatigue, lightheadedness, presyncope, and syncope.  ECG typically demonstrates bradycardia with sinus pauses (delayed P waves), sinus arrest (dropped P waves), and junctional escape beats.

A 60-Year-Old Man Comes to the Emergency Department Because of a 3-Day