A 37-year-old man with no significant past medical history presents

USMLE Question Break Down Cardiology

Welcome back to MedSmarter’s USMLE Style Question of the Week. Here’s the breakdown of another high-yield Cardiology question for those preparing for your USMLE Step 1 or just to gain some knowledge. As always you want to begin with reading the last sentence of the vignette first to get an understanding of what the question is asking for.

Question Break Down of the Week:

A 37-year-old man with no significant past medical history presents to his primary care physician complaining of shortness of breath on exertion for the past several months. The patient also acknowledges recent heart palpitations, but denies cough, chest pain, lower extremity edema, nocturnal dyspnea, or weakness. He further denies any recent illness, and he states that he does not smoke. Cardiac exam shows an irregularly irregular rhythm, a widely split and fixed S2, as well as a mid-systolic ejection murmur over the left upper sternal border. ECG reveals that the patient is in atrial fibrillation. Based on these findings, the physician concludes that these symptoms are due to pathology of which of the following fetal structures?

A) Aorticopulmonary septum
B) Ductus arteriosus
C) Ductus venosus
D) Foramen ovale
E) Interventricular septum

The correct answer choice is E. The physician concludes that the patient’s symptoms are due to pathology of this fetal structure based on the patient’s irregularly irregular rhythm, widely split and fixed S2, mid systolic ejection murmur over the left upper sternal border, and ECG showing atrial fibrillation. The other answer choices, including ductus arteriosus, aortopulmonary septum, ductus venosus, and interventricular septum, are all ruled out based on their inability to cause the specific symptoms and signs seen in this patient.

It tells that patent foramen ovale is a communication between the venous side and the arterial side of the heart that typically closes shortly after birth. However, in some cases, the communication remains open and can cause atrial fibrillation, which is the cause of the patient’s irregularly irregular pulse, as well as palpitations. Additionally, a patent foramen ovale can lead to paradoxical emboli, which can cause strokes in patients who shouldn’t have strokes coming from the venous side of the body. This matches the patient’s symptoms and the findings on the physical exam and ECG, making E the correct answer.

Did you think the answer was different?

Did you think that the correct answer choice was other than E? You can view this video for a deeper discussion of why A, B, C, and D are not the correct answer choices.

Learn to correctly answer basic science knowledge questions and prepare to take your USMLE Step 1 exam. The MedSmarter roadmap will make your journey to becoming a practicing physician in the United States as painless as possible.

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