While climbing a flight of stairs at a shopping mall, a 72-year-old man experiences a sudd… — USMLE Step 3

While climbing a flight of stairs at a shopping mall, a $72$ -year-old man experiences a sudden loss of consciousness. Bystanders report that he collapsed without warning but regained full orientation within a minute of falling. He arrives at the emergency department via private vehicle thirty minutes later. His past medical history is significant for essential hypertension and hyperlipidemia. Current medications include lisinopril and atorvastatin. On arrival, he is asymptomatic and alert. Vital signs show a temperature of $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure of $138/82\text{ mmHg}$ , heart rate of $78\text{/min}$ , and respiratory rate of $14\text{/min}$ . Physical examination reveals a late-peaking, harsh systolic murmur heard best at the right second intercostal space with radiation to the neck. The lungs are clear to auscultation. A 12-lead electrocardiogram demonstrates voltage criteria for left ventricular hypertrophy and normal sinus rhythm with no ST-segment or T-wave abnormalities. Which of the following is the most appropriate next diagnostic study for this patient?

Transthoracic echocardiographyCevap
B
Carotid duplex ultrasonography
C
Ambulatory 24-hour electrocardiography
D
Computed tomography angiography of the chest
E
Exercise treadmill stress testing

Cevap

Transthoracic echocardiography

Transthoracic echocardiography is the most appropriate next diagnostic study. The patient's presentation of exertional syncope coupled with a late-peaking, harsh systolic murmur radiating to the neck and left ventricular hypertrophy on ECG is highly suspicious for symptomatic, severe aortic stenosis. Exertion causes peripheral vasodilation to increase blood flow to muscles, but the critically stenotic aortic valve prevents a compensatory increase in cardiac output. This mismatch leads to acute cerebral hypoperfusion and subsequent syncope. Echocardiography is the gold standard initial test to visualize the valve, measure the transvalvular gradient, and assess left ventricular function.

Adım Adım Çözüm

Analyze the clinical presentation of syncope.

The patient experienced exertional syncope with a rapid and complete recovery.

Exertional syncope points strongly toward a structural cardiac abnormality (like outflow obstruction) rather than a vasovagal or primary neurologic cause.

Correlate history with physical examination and electrocardiogram findings.

The physical exam reveals a late-peaking systolic murmur radiating to the neck, and the ECG shows left ventricular hypertrophy.

These findings are classic for severe aortic stenosis, which causes a fixed cardiac output leading to cerebral hypoperfusion during exertion.

Select the safest, most definitive initial diagnostic test based on the suspected etiology.

Transthoracic echocardiography is selected to confirm the diagnosis.

Echocardiography provides non-invasive, definitive assessment of valve morphology, transvalvular pressure gradients, and ventricular function without exposing the patient to the risks of exertion.

Anahtar Kavram

Patients presenting with exertional syncope and a characteristic late-peaking systolic murmur radiating to the carotids require prompt transthoracic echocardiography to evaluate for severe aortic stenosis. Provocative testing like exercise stress testing is strictly contraindicated.

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