A 23-year-old woman presents to the emergency department with a 4-day history of progressive shortness of breath and chest pain. The pain is sharp, worsens with inspiration, and improves when she leans forward. She recently recovered from a viral upper respiratory infection. Her medical history is unremarkable, and she takes no medications. On physical examination, her temperature is 38.3°C (100.9°F), heart rate is 110 beats/min, and blood pressure is 118/75 mm Hg. On auscultation, a scratchy, high-pitched sound is heard at the left lower sternal border, which is present throughout the cardiac cycle. An electrocardiogram (ECG) shows diffuse ST-segment elevation in most leads and PR-segment depression in lead II.

Which of the following is the most likely underlying mechanism causing this patient's condition?

A) Autoimmune destruction of the myocardium
B) Lymphocytic infiltration of the pericardium
C) Granulomatous inflammation of the pericardium
D) Deposition of immune complexes in the myocardium
E) Mycobacterial infection of the pericardium

🧠 Correct Answer: Lymphocytic infiltration of the pericardium

• The patient's recent viral infection, typical symptoms (pleuritic chest pain, friction rub), and ECG findings are consistent with acute viral pericarditis, confirming lymphocytic infiltration.

Viral Upper Respiratory Infection
↓
🧠 Immune system detects viral antigens
↓
Activation of immune response (T-cells & cytokines) → Lymphocytic infiltration of the pericardium
↓
🧠 Inflammation of the pericardium
↓
Pericardial friction ↑ → Scratchy pericardial friction rub (auscultation)
↓
Pericardial irritation → Pain (worsens with inspiration, improves when leaning forward)
↓
Cytokines ↑ (localized inflammation) → Fever (↑ temperature)
↓
🧠 Inflammatory changes spread → Electrical conduction affected (ECG findings)

• Diffuse ST-segment elevation (global pericardial involvement)

• PR-segment depression (due to inflammation near the atria)

  

  Image from UCSF

  

Explanation of Incorrect Answers:

• Autoimmune destruction of the myocardium:
  🧠 Seen in myocarditis (not pericarditis); lacks pericardial friction rub and PR-segment depression.

• Granulomatous inflammation of the pericardium:
  🧠 Associated with tuberculous pericarditis or sarcoidosis (not viral origin), typically with chronic symptoms.

• Deposition of immune complexes in the myocardium:
  🧠 Seen in immune-mediated myocarditis, affecting the myocardium (not the pericardium) with no friction rub.

• Mycobacterial infection of the pericardium:
  🧠 Typically chronic, related to tuberculosis, with signs like constrictive pericarditis, not acute viral symptoms.

Flashcards

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