Differential Diagnosis for a 78-year-old Male with Worsening Shortness of Breath

The patient's presentation of worsening shortness of breath, chills, subjective fever, and a history of severe COPD, aortic aneurysm, and chronic low blood pressure, suggests a complex clinical picture. The differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis
  • COPD Exacerbation: Given the patient's history of severe COPD and prior hospitalizations for COPD exacerbations, this is the most likely diagnosis. The worsening shortness of breath, chills, and subjective fever are consistent with an exacerbation, which can be triggered by a respiratory infection.
• Other Likely Diagnoses
  • Pneumonia: The presence of chills, subjective fever, and worsening respiratory symptoms could indicate pneumonia, especially in a patient with underlying COPD.
  • Pulmonary Embolism (PE): Although the patient denies chest pain, PE should be considered, especially given the patient's history of atrial fibrillation and use of Eliquis, which may not completely eliminate the risk of PE.
  • Congestive Heart Failure (CHF) Exacerbation: The patient's history of atrial fibrillation and symptoms of worsening shortness of breath could suggest a CHF exacerbation, particularly if there is underlying cardiac dysfunction.
• Do Not Miss Diagnoses
  • Aortic Dissection or Rupture: Given the patient's history of aortic aneurysm, any worsening or change in symptoms could indicate a life-threatening aortic event. The "heavy and funny" feeling in the legs could be indicative of decreased perfusion.
  • Sepsis: The combination of subjective fever, chills, and worsening respiratory status could indicate sepsis, particularly if there is an underlying infection.
  • Cardiac Ischemia: Although the patient denies chest pain, cardiac ischemia should be considered, especially in the context of atrial fibrillation and potential for decreased cardiac output.
• Rare Diagnoses
  • Pulmonary Vasculitis: Conditions like Wegener's granulomatosis or other forms of vasculitis could present with worsening respiratory symptoms and systemic signs like fever and chills, although these are less common.
  • Lymphangitic Carcinomatosis: Metastatic cancer to the lungs could cause worsening shortness of breath, although this would be less likely without other symptoms or a known history of cancer.

Workup

The workup for this patient should include:

• Complete blood count (CBC) to evaluate for signs of infection or inflammation
• Blood cultures to rule out sepsis
• Electrocardiogram (ECG) to evaluate for cardiac ischemia or arrhythmias
• Chest X-ray to assess for pneumonia, CHF, or other pulmonary abnormalities
• D-dimer to help rule out pulmonary embolism, although its utility may be limited in this clinical context
• Arterial blood gas (ABG) to assess the severity of respiratory compromise
• Echocardiogram to evaluate cardiac function and rule out CHF
• CT angiogram of the chest if aortic dissection is suspected
• Consideration for bronchoscopy if there's suspicion of an obstructive process or need for cultures

This comprehensive approach will help narrow down the differential diagnosis and guide appropriate management.