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Difficulty: MediumDiagnostic Workup and Test Sequencing

An emergency medical services team brings a 68-year-old male to the hospital after he lost consciousness while walking up a flight of stairs. Witnesses state that he collapsed suddenly without any preceding diaphoresis, palpitations, or visual changes. He regained full alertness within approximately one minute and had no post-event confusion. His blood pressure is 112/82 mm Hg and his heart rate is 76/min. Cardiac auscultation reveals a harsh, late-peaking systolic murmur at the right upper sternal border that radiates to the neck. Palpation of the carotid arteries demonstrates a delayed and diminished upstroke. The neurological examination is completely unremarkable. Which of the following diagnostic studies are indicated as the initial concurrent steps in this patient's evaluation? (Select exactly two)

  1. 12-lead electrocardiographyAnswer
  2. Transthoracic echocardiographyAnswer
  3. C
    Computed tomography of the head without contrast
  4. D
    Carotid duplex ultrasonography
  5. E
    Ambulatory 24-hour electrocardiographic monitoring

Answer

The initial concurrent steps for evaluating this patient are 12-lead electrocardiography and transthoracic echocardiography.
The patient's presentation of exertional syncope, along with a delayed carotid upstroke (pulsus parvus et tardus) and a harsh, late-peaking systolic murmur, is the classic clinical picture of severe aortic stenosis. In all patients presenting with syncope, a 12-lead electrocardiogram is the mandatory first step to evaluate for baseline electrical abnormalities. Because there is a high clinical suspicion for structural heart disease causing fixed cardiac output, a transthoracic echocardiogram must be ordered concurrently to visualize the aortic valve, measure the transvalvular gradient, and evaluate left ventricular function.

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient experienced exertional syncope with rapid recovery. Physical exam shows a late-peaking systolic murmur and pulsus parvus et tardus (diminished and delayed carotid upstroke).
Identifying the pattern of syncope (exertional) and associated signs helps localize the underlying etiology.
2
Formulate the most likely differential diagnosis.
The findings are highly specific for severe aortic stenosis. Exertional syncope occurs because the fixed cardiac output cannot meet the increased peripheral demands of exercise.
A narrow differential diagnosis drives the selection of targeted, cost-effective diagnostic tests.
3
Select the guideline-concordant initial diagnostic steps.
A 12-lead electrocardiogram is universally required for syncope evaluation. Simultaneously, a transthoracic echocardiogram is needed to quantify the severity of the suspected aortic stenosis.
Appropriate test sequencing dictates using highly sensitive screening and non-invasive structural tests prior to invasive, prolonged, or unrelated systemic imaging.

Key Concept

Patients with exertional syncope and physical exam findings suggestive of severe aortic stenosis require immediate evaluation with both a 12-lead electrocardiogram and a transthoracic echocardiogram to assess electrical conduction and structural valve hemodynamics.
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Diagnostic Workup and Test Sequencing

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