Differential Diagnosis for Fatigue and 57 bpm

• Single most likely diagnosis
  • Hypothyroidism: A common condition that can cause fatigue and bradycardia (heart rate of 57 bpm is considered bradycardia in adults). The slowed metabolism in hypothyroidism can lead to both symptoms.
• Other Likely diagnoses
  • Anemia: Can cause fatigue due to reduced oxygen delivery to tissues. While anemia itself doesn't directly cause bradycardia, severe cases might lead to a compensatory decrease in heart rate.
  • Dehydration: Can lead to fatigue and potentially bradycardia, especially if severe, due to decreased blood volume and cardiac output.
  • Sleep Apnea: Though not directly causing bradycardia, sleep apnea can lead to significant fatigue. The intermittent hypoxia and frequent awakenings disrupt normal sleep patterns.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Myocardial Infarction (MI) or Cardiac Ischemia: Though less common, MI can present atypically with fatigue and bradycardia, especially in diabetic or elderly patients. Missing this diagnosis can be fatal.
  • Infectious Diseases (e.g., Endocarditis, Lyme Disease): Certain infections can cause both fatigue and heart rate abnormalities, including bradycardia. These conditions require prompt diagnosis and treatment to prevent serious complications.
  • Adrenal Insufficiency: A life-threatening condition that can cause fatigue, hypotension, and potentially bradycardia due to the lack of cortisol and aldosterone.
• Rare diagnoses
  • Sick Sinus Syndrome: A condition affecting the sinoatrial node, leading to abnormal heart rhythms, which can include bradycardia and potentially cause fatigue.
  • Neuromuscular Disorders (e.g., Myasthenia Gravis): Though primarily affecting muscle strength, certain neuromuscular disorders can have systemic effects, including fatigue and, less commonly, heart rate abnormalities.