A 48-year-old man is evaluated in the hospital for new-onset exertional dyspnea, fatigue, … — USMLE Step 2 CK

A $48$ -year-old man is evaluated in the hospital for new-onset exertional dyspnea, fatigue, and lightheadedness over the past $24$ hours. He was admitted $6$ days ago for native aortic valve infective endocarditis caused by *Streptococcus mitis*. Blood cultures demonstrated that the organism is highly susceptible to penicillin, and he has been receiving targeted intravenous aqueous crystalline penicillin G. His temperature is $37.4^\circ\text{C}$ ( $99.3^\circ\text{F}$ ), blood pressure is $102/60 \text{ mm Hg}$ , pulse is $42/\text{min}$ , and respirations are $18/\text{min}$ . Physical examination reveals a harsh, early diastolic decrescendo murmur at the left sternal border. The lungs are clear to auscultation. Electrocardiogram reveals sinus rhythm with a PR interval of $280 \text{ ms}$ (first-degree atrioventricular block) and a new left bundle branch block. Laboratory studies show a leukocyte count of $8,500/\text{mm}^3$ , a thyroid-stimulating hormone (TSH) level of $0.2 \text{ \mu U/mL}$ (Normal: $0.4$ - $4.0 \text{ \mu U/mL}$ ), and a free T4 of $0.7 \text{ ng/dL}$ (Normal: $0.9$ - $2.4 \text{ ng/dL}$ ). The patient is currently lethargic and lacks medical decision-making capacity. His brother is at the bedside and demands that the medical team immediately switch the antibiotics to a "stronger" regimen, but the patient's advance directive legally appoints his wife, who is en route to the hospital, as his healthcare proxy. Which of the following is the most appropriate next step in the management of this patient?

Perform a transesophageal echocardiogramAnswer
B
Switch therapy to intravenous vancomycin and cefepime
C
Administer inhaled albuterol and intravenous corticosteroids
D
Initiate oral levothyroxine therapy
E
Obtain consent from the patient's brother to modify the treatment plan

Answer

The correct answer is to perform a transesophageal echocardiogram.

This patient has aortic valve infective endocarditis and now presents with a new-onset atrioventricular conduction delay (prolonged PR interval) and a left bundle branch block, resulting in symptomatic bradycardia (dyspnea and lightheadedness). The aortic valve annulus is anatomically contiguous with the interventricular septum, which houses the atrioventricular (AV) node and the bundle of His. The development of a new conduction block in the setting of infective endocarditis is highly suggestive of the infection extending beyond the valve leaflets to form a perivalvular abscess. A perivalvular abscess is a severe complication that typically requires prompt surgical intervention (e.g., valve replacement and debridement). Transesophageal echocardiography (TEE) provides high-resolution imaging of the aortic root and is the diagnostic test of choice to confirm the presence of a perivalvular abscess.

Step-by-Step Solution

Analyze the patient's new clinical findings.

The patient developed new-onset bradycardia, dyspnea, and electrocardiographic conduction abnormalities (first-degree AV block and left bundle branch block).

Identifying the onset of new symptoms helps localize the complication.

Correlate the findings with the underlying diagnosis of aortic valve endocarditis.

The aortic valve is anatomically adjacent to the AV node and the bundle of His. Extension of the infection from the valve into the adjacent myocardium forms a perivalvular abscess, disrupting the conduction system.

Understanding cardiac anatomy is required to recognize that conduction blocks in endocarditis strongly suggest local abscess formation.

Determine the optimal diagnostic modality for the suspected complication.

Transesophageal echocardiography (TEE) provides superior visualization of the posterior structures of the heart and the aortic root compared to transthoracic echocardiography.

TEE is the gold standard for diagnosing a perivalvular abscess, which dictates the need for urgent surgical intervention.

Key Concept

New-onset atrioventricular conduction abnormalities in a patient with infective endocarditis (especially of the aortic valve) should immediately raise suspicion for a perivalvular abscess, which is best diagnosed with a transesophageal echocardiogram.

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