COMSAE Form 103: High-Yield Practice
Questions with Answers and Rationales
Question 1
,A 65-year-old man presents with crushing substernal chest pain radiating to his left arm. ECG
shows ST-segment elevation in leads II, III, and aVF. Which artery is most likely occluded?
A. Left anterior descending artery
B. Left circumflex artery
C. Right coronary artery
D. Posterior descending artery
Answer: C. Right coronary artery
Rationale: ST elevations in leads II, III, and aVF indicate an inferior wall myocardial infarction. In
most individuals, the right coronary artery supplies the inferior wall of the left ventricle. The LAD
supplies the anterior wall, and the circumflex supplies the lateral wall.
Question 2
,Which electrolyte is the primary determinant of extracellular fluid volume?
A. Potassium
B. Calcium
C. Sodium
D. Magnesium
Answer: C. Sodium
Rationale: Sodium is the major extracellular cation and the primary determinant of plasma
osmolarity and extracellular fluid volume. Changes in sodium levels directly affect water balance
and blood pressure regulation.
Question 3
A patient with untreated Graves disease is at highest risk for which cardiac complication?
, A. Aortic stenosis
B. Bradyarrhythmia
C. Atrial fibrillation
D. Constrictive pericarditis
Answer: C. Atrial fibrillation
Rationale: Thyrotoxicosis increases β-adrenergic activity and cardiac output, predisposing patients
to atrial fibrillation. Hyperthyroidism should be considered in any patient presenting with new-onset
atrial fibrillation, especially in younger patients without other risk factors.
Question 4
Which cell type is the primary target of HIV infection?
Questions with Answers and Rationales
Question 1
,A 65-year-old man presents with crushing substernal chest pain radiating to his left arm. ECG
shows ST-segment elevation in leads II, III, and aVF. Which artery is most likely occluded?
A. Left anterior descending artery
B. Left circumflex artery
C. Right coronary artery
D. Posterior descending artery
Answer: C. Right coronary artery
Rationale: ST elevations in leads II, III, and aVF indicate an inferior wall myocardial infarction. In
most individuals, the right coronary artery supplies the inferior wall of the left ventricle. The LAD
supplies the anterior wall, and the circumflex supplies the lateral wall.
Question 2
,Which electrolyte is the primary determinant of extracellular fluid volume?
A. Potassium
B. Calcium
C. Sodium
D. Magnesium
Answer: C. Sodium
Rationale: Sodium is the major extracellular cation and the primary determinant of plasma
osmolarity and extracellular fluid volume. Changes in sodium levels directly affect water balance
and blood pressure regulation.
Question 3
A patient with untreated Graves disease is at highest risk for which cardiac complication?
, A. Aortic stenosis
B. Bradyarrhythmia
C. Atrial fibrillation
D. Constrictive pericarditis
Answer: C. Atrial fibrillation
Rationale: Thyrotoxicosis increases β-adrenergic activity and cardiac output, predisposing patients
to atrial fibrillation. Hyperthyroidism should be considered in any patient presenting with new-onset
atrial fibrillation, especially in younger patients without other risk factors.
Question 4
Which cell type is the primary target of HIV infection?
