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USMLE® Step 1 Question of the Day: Dyspnea on Exertion

Osmosis Team
Published on May 5, 2021. Updated on May 5, 2021.

Each week, Osmosis shares a USMLE® Step 1-style practice question to test your knowledge of medical topics. Today's case involves a 70-year-old woman who suffers from worsening fatigue, dyspnea on exertion, and lower extremity swelling. Transthoracic echocardiography demonstrates a dilated left ventricle and increased end-diastolic volume, and wall motion abnormalities are noted along the anterolateral heart border. Can you figure it out?

A 70-year-old woman comes to the emergency department due to a three week history of worsening fatigue, dyspnea on exertion, and lower extremity swelling. Her past medical history is significant for hypertension and hyperlipidemia, but notes no recent travel, sick contacts, or illnesses. She recalls one episode of nausea and diaphoresis while she was lifting boxes at home approximately one month ago, but she does not recall any chest pain or shortness of breath at that time. She is a life-time non-smoker and reports drinking one glass of wine every night with dinner. Her temperature is 37.2°C (98.9° F), pulse is 75/min, respirations are 18/min, and blood pressure is 142/82 mmHg. Physical examination shows 2+ pitting edema of the lower extremities and prominent jugular veins. An additional heart sound is heard just after S2, and faint bibasilar crackles are heard on auscultation of the lungs. Transthoracic echocardiography demonstrates a dilated left ventricle and increased end-diastolic volume, and wall motion abnormalities are noted along the anterolateral heart border. Ejection fraction by visualization is estimated at 34%. Which of the following best describes the underlying cause of this patient’s symptoms?

A. Long-standing untreated hypertension 

B. Ischemic heart disease 

C. Repetitive vasoconstriction of pulmonary vasculature 

D. Alcohol consumption 

E. Infection with a positive-sense single-stranded RNA virus

Scroll down to find the answer!



The correct answer to today's USMLE® Step 1 Question is...

B. Ischemic heart disease 

Before we get to the Main Explanation, let's look at the incorrect answer explanations. Skip to the bottom if you want to see the correct answer right away!

Incorrect answer explanations

The incorrect answers to today's USMLE® Step 1 Question are...

A. Long-standing untreated hypertension

Incorrect: Long standing untreated hypertension typically results in findings of diastolic heart failure due to concentric hypertrophy. Findings include a preserved ejection fraction and a normal end-diastolic volume. The patient in this vignette has an increased end diastolic volume and a reduced ejection fraction making an etiology of systolic heart failure more likely.

C. Repetitive vasoconstriction of pulmonary vasculature

Incorrect: This answer choice describes the pathophysiology of chronic smoking and COPD leading to cor pulmonale or isolated right sided heart failure. Prolonged vasoconstriction of pulmonary vasculature increases demand on the right heart, eventually leading to peripheral edema and hepatic congestion without pulmonary edema. The patient in this vignette has findings of pulmonary edema and is not a smoker, making this diagnosis less likely.

D. Alcohol consumption

Incorrect: Alcohol can cause dilated cardiomyopathy and systolic heart failure; however, this occurs only with heavy consumption. The patient in this vignette is described as consuming within the recommended drink limit per day, making this diagnosis unlikely.

E. Infection with a positive-sense single-stranded RNA virus

Incorrect: This question stem describes the pathophysiology of a dilated cardiomyopathy from coxsackie B virus, which can cause systolic heart failure (as seen in this patient). This answer choice is less likely in this patient without a recent history of infectious illness.

Main explanation

Systolic heart failure is most commonly due to ischemia or myocardial infarction, which causes decreased cardiac contractility that leads to systolic dysfunction. The inability of the heart to effectively pump blood forward through circulation results in clinical features of left-sided heart failure causing pulmonary edema: fatigue, dyspnea, orthopnea, paroxysmal nocturnal dyspnea, as well as bibasilar crackles and an S3 heart sound (ventricular gallop) on examination. This often progresses to right-sided heart failure, resulting in jugular venous distention (JVD), pitting edema, and hepatic congestion. The patient in this question likely suffered an atypical or silent myocardial infarction while she was moving boxes several weeks ago, and without appropriate treatment, she has now developed systolic heart failure. Other causes of systolic heart failure include etiologies of dilated cardiomyopathy including alcohol, coxsackie B virus infection, chronic cocaine use, or Chagas disease. Echocardiography typically shows an increased end diastolic volume (EDV), decreased contractility (or wall motion abnormalities), and reduced ejection fraction (EF).


In contrast to systolic heart failure, diastolic heart failure is most commonly due to cardiac hypertrophy from long-standing, untreated hypertension. It presents with the same clinical features as systolic heart failure. Echocardiographic findings generally demonstrate a preserved EF and a normal EDV. Patients with diastolic heart failure will also have decreased compliance (increased end diastolic pressure) due to stiff ventricular walls. Other etiologies of diastolic heart failure include infiltrative diseases such as amyloidosis, sarcoidosis, or post-radiation fibrosis.                                                                                          

Major Takeaway

Systolic heart failure is most commonly due to ischemia or prior myocardial infarction. It presents with all the typical clinical features of heart failure, and will demonstrate increased end-diastolic volume and a reduced ejection fraction on echocardiography.

References 

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The United States Medical Licensing Examination (USMLE®) is a joint program of the Federation of State Medical Boards (FSMB®) and National Board of Medical Examiners (NBME®). Osmosis is not affiliated with NBME nor FSMB.