Differential Diagnosis for a 46-year-old Man with Chest Pain and Recent Myocardial Infarction

The patient's symptoms and physical examination findings suggest a condition related to the recent myocardial infarction. Here's a categorized differential diagnosis:

• Single most likely diagnosis

  • Pericarditis: The sharp pain behind the sternum that worsens with coughing and improves with sitting forward, along with a scratchy superficial sound (pericardial friction rub) at the left sternal edge and muffled heart sounds, are classic signs of pericarditis. Pericarditis is a known complication of myocardial infarction, occurring in the first few weeks after the event.

• Other Likely diagnoses

  • Pulmonary embolism: Although less likely given the specific symptoms and signs, pulmonary embolism could cause chest pain and increased JVP. However, the presence of a pericardial friction rub and the nature of the pain make this less likely.
  • Congestive heart failure: The ascites and elevated JVP could suggest heart failure, which is a possible complication of myocardial infarction. However, the specific chest pain characteristics and pericardial friction rub point more towards pericarditis.

• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)

  • Cardiac tamponade: Although the patient's symptoms and signs do not fully align with cardiac tamponade (e.g., hypotension is not mentioned), the presence of ascites, elevated JVP, and muffled heart sounds could be indicative of a developing tamponade, especially if the pericarditis progresses to involve significant fluid accumulation.
  • Ventricular septal rupture or free wall rupture: These are rare but life-threatening complications of myocardial infarction that could present with chest pain and signs of heart failure. Immediate diagnosis and surgical intervention are crucial.

• Rare diagnoses

  • Pneumonia or pleuritis: Could cause chest pain that worsens with coughing, but the pericardial friction rub and other cardiac findings make these less likely.
  • Aortic dissection: A life-threatening condition that could cause sharp chest pain, but it is less likely given the context of recent myocardial infarction and the specific findings suggestive of pericarditis.

In terms of the ECG changes, C. Diffuse ST elevation is the most likely finding in pericarditis, which is the single most likely diagnosis based on the clinical presentation.