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USMLE® Step 1 Question of the Day: Episode of Syncope

Osmosis Team
Published on Jun 22, 2022. Updated on Jun 21, 2022.

This week, we are sharing another USMLE® Step 1-style practice question to test your knowledge of medical topics. Today's case involves a 75-year-old man who lost consciousness for one minute following an episode of syncope two days ago. Can you figure out in which area cardiac auscultation will most likely reveal a murmur?

A 75-year-old man comes to his primary care physician’s office accompanied by his partner following an episode of syncope two days ago. The patient was working in his garden when he suddenly felt light headed and lost consciousness for one minute. His partner, who witnessed the incident, states that he did not jerk uncontrollably or hit his head. The patient endorses worsening shortness of breath and occasional chest pain during his usual morning walk for the past month. Medical history includes benign prostatic hyperplasia, which is managed with finasteride. His temperature is 36.0°C (96.8°F), pulse is 75/min, and blood pressure is 138/87 mmHg. On physical examination, the lungs are clear to auscultation. Neurologic examination is within normal limits. ECG demonstrates voltage criteria for left ventricular hypertrophy. 

Cardiac auscultation will most likely reveal a murmur in which of the areas marked on the diagram below?

Osmosis diagram with numbers.

A. Area 1: Crescendo-decrescendo systolic murmur

B. Area 2: Ejection murmur accompanied by a fixed split-second heart sound (S2)

C. Area 3: Systolic ejection murmur

D. Area 4: Holosystolic murmur

E. Area 5: Opening snap followed by diastolic murmur

Scroll down to find the answer!


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

A. Area 1: Crescendo-decrescendo systolic murmur

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...

B. Area 2: Ejection murmur accompanied by a fixed split-second heart sound (S2)

Incorrect: Ejection murmur accompanied by a fixed split-second heart sound (S2) over the left 2nd intercostal space (pulmonic area) can be auscultated with atrial septal defects. Patients with small ASDs are usually asymptomatic.

C. Area 3: Systolic ejection murmur

Incorrect: A systolic ejection murmur over the 3rd right intercostal space is associated with hypertrophic obstructive cardiomyopathy (HOCM). Patients with HOCM are usually young and present with dyspnea on exertion, fatigue, atypical or anginal chest pain, syncope, palpitations, and sudden cardiac death.

D. Area 4: Holosystolic murmur

Incorrect: A holosystolic murmur can be heard over the 4th left intercostal space (tricuspid area) in patients with tricuspid regurgitation and ventricular septal defects. Tricuspid regurgitation often presents with signs of right-sided heart failure (HF), including hepatic congestion, ascites, and peripheral edema. Mild VSDs may be asymptomatic, while large VSDs may induce heart failure.

E. Area 5: Opening snap followed by diastolic murmur

Incorrect: An opening snap followed by a rumbling and mid-to-late diastolic murmur best heard at the 5th left midclavicular intercostal space (mitral area) is indicative of mitral stenosis (MS). Clinical features of MS include dyspnea, chest pain, atrial fibrillation, pulmonary hypertension, and hoarseness secondary to left atrial enlargement.

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Main Explanation

This patient presents with features of aortic stenosis (AS) including exertional dyspnea, chest pain, and syncope. On physical examination, AS is heard as a crescendo-decrescendo systolic ejection murmur over the right 2nd intercostal space.

AS is the most common cause of left ventricular outflow obstruction and is commonly associated with age-related calcifications in patients over the age of sixty, though it can manifest in younger patients due to bicuspid aortic valve or rheumatic heart disease. Common clinical findings include exertional dyspnea, decreased exercise tolerance, dizziness, syncope, exertional angina, and arrhythmias. During exertion, left ventricular dysfunction ensues as the heart pumps against a stenotic valve--thus limiting ejection fraction and blood flow to both peripheral tissues and coronary arteries. Additional physical exam findings include an S2, ejection click, or weak carotid pulse with a delayed peak (“Pulsus parvus et tardus”). An early-peaking murmur typically correlates with mild to moderate AS, whereas a late-peaking murmur often indicates severe AS.

Osmosis diagram with notes.

Major Takeaway

Aortic stenosis is auscultated as a crescendo-decrescendo systolic ejection murmur over the right 2nd intercostal space. A late-peaking murmur usually correlates with severe stenosis.

References

Lindman BR, Clavel MA, Mathieu P, et al. Calcific aortic stenosis. Nat Rev Dis Primers 2016; 2:16006.

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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.