A 69-year-old man presents to the clinic complaining of a persistent dry cough, progressiv… — USMLE Step 2 CK

A $69$ -year-old man presents to the clinic complaining of a persistent dry cough, progressive shortness of breath on exertion, and worsening fatigue over the last two months. He also notes new-onset anxiety and difficulty sleeping due to his respiratory distress. His past medical history is significant for ischemic cardiomyopathy with a reduced ejection fraction and recurrent symptomatic sustained ventricular tachycardia, for which he takes amiodarone, lisinopril, carvedilol, escitalopram, and rivaroxaban. He has a $10$ -pack-year smoking history but quit $15$ years ago. Vital signs include a blood pressure of $112/68\text{ mmHg}$ , a heart rate of $64/\text{min}$ , a respiratory rate of $22/\text{min}$ , and an oxygen saturation of $91\%$ on ambient air. Physical examination reveals fine, late-inspiratory crackles at both lung bases. The jugular venous pressure is $6\text{ cm H}_2\text{O}$ . There is no lower extremity edema. Laboratory studies show a leukocyte count of $8,200/\text{mm}^3$ , a serum thyroid-stimulating hormone (TSH) level of $8.5\text{ \mu U/mL}$ (normal: $0.4-4.0\text{ \mu U/mL}$ ), and a free thyroxine (T4) level of $0.6\text{ ng/dL}$ (normal: $0.8-1.8\text{ ng/dL}$ ). His B-type natriuretic peptide (BNP) level is $145\text{ pg/mL}$ (similar to a baseline of $150\text{ pg/mL}$ three months ago). An electrocardiogram demonstrates normal sinus rhythm with a QTc interval of $475\text{ ms}$ . High-resolution computed tomography of the chest reveals peripheral, bilateral ground-glass opacities with associated septal thickening. Which of the following is the most appropriate next step in the management of this patient?

Discontinuation of amiodarone and initiation of systemic glucocorticoidsAnswer
B
Administration of intravenous torsemide and application of positive pressure ventilation
C
Admission for empiric therapy with intravenous cefepime and vancomycin
D
Continuation of current antiarrhythmic therapy and initiation of oral methimazole
E
Initiation of oral haloperidol to manage acute anxiety secondary to his respiratory distress

Answer

The most appropriate management is the discontinuation of amiodarone and initiation of systemic glucocorticoids.

The correct intervention involves stopping amiodarone and starting systemic corticosteroids. The patient is exhibiting classic signs of amiodarone-induced pulmonary toxicity, which typically presents with an indolent onset of exertional dyspnea, nonproductive cough, bilateral crackles, and patchy ground-glass opacities on high-resolution chest CT. Normal right-sided heart pressures (normal JVP) and an un-elevated BNP effectively rule out a concurrent exacerbation of his ischemic cardiomyopathy. Furthermore, the patient simultaneously exhibits amiodarone-induced hypothyroidism (elevated TSH, low T4). The mainstay of therapy for symptomatic amiodarone pulmonary toxicity is immediate drug cessation and a prolonged taper of systemic glucocorticoids to prevent irreversible pulmonary fibrosis.

Step-by-Step Solution

Analyze the clinical presentation and timing.

The patient has a 2-month history of progressive dyspnea and cough with ground-glass opacities, which suggests an interstitial lung process rather than an acute infection or acute fluid overload.

Differentiating between acute (e.g., ADHF, pneumonia) and subacute/chronic (e.g., drug toxicity, interstitial lung disease) etiologies is crucial for accurate diagnosis.

Correlate imaging and physical exam findings with the patient's medication list.

The patient's normal JVP and baseline BNP rule out a heart failure exacerbation. His use of amiodarone directly correlates with the diagnosis of amiodarone-induced interstitial pneumonitis.

Amiodarone is a class III antiarrhythmic with multi-organ toxicities, prominently including pulmonary toxicity (interstitial pneumonitis) and thyroid dysfunction.

Determine the definitive treatment for the identified condition.

The primary treatment for symptomatic amiodarone pulmonary toxicity is immediate withdrawal of the medication and administration of systemic corticosteroids.

Continuing the drug can lead to irreversible pulmonary fibrosis and fatal respiratory failure.

Key Concept

Diagnosis and management of amiodarone-induced pulmonary toxicity.

Estimated Time:1m 30s

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