1. A 65-year-old man with a history of hypertension, diabetes, and

chronic kidney disease presents to the emergency department

with shortness of breath, chest pain, and palpitations. He is

diagnosed with atrial fibrillation and is started on anticoagulation

therapy. Which of the following is the most likely underlying

pathophysiological mechanism of his atrial fibrillation?

A) Increased sympathetic tone

B) Electrical reentry

C) Myocardial ischemia

D) Ventricular hypertrophy

Answer: B) Electrical reentry

Rationale: Atrial fibrillation is a common arrhythmia that results

from multiple reentrant wavelets of electrical activity in the atria,

causing irregular and rapid atrial contractions. The reentry can be

triggered by factors such as hypertension, diabetes, ischemia,

inflammation, or electrolyte imbalance, which alter the atrial

tissue properties and create areas of slow conduction or

unidirectional block. Electrical reentry is the most common

mechanism of atrial fibrillation, while increased sympathetic tone,

myocardial ischemia, and ventricular hypertrophy are more likely

to cause other types of arrhythmias.

2. A 50-year-old woman with a history of rheumatoid arthritis and

osteoporosis is admitted to the hospital with a fever, cough, and

dyspnea. She is diagnosed with community-acquired pneumonia

and is started on antibiotics. A chest X-ray reveals a right lower

lobe consolidation. Which of the following is the most likely

pathophysiological process that leads to the formation of

consolidation in pneumonia?

A) Alveolar collapse

B) Bronchial obstruction

C) Inflammatory exudate

D) Pulmonary edema

Answer: C) Inflammatory exudate