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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
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