Differential Diagnosis for Fainting

• Single most likely diagnosis:
  • Vasovagal syncope: This is the most common cause of fainting, often triggered by stress, pain, or prolonged standing, leading to a sudden drop in blood pressure and heart rate.
• Other Likely diagnoses:
  • Orthostatic hypotension: A drop in blood pressure upon standing, which can be due to dehydration, medication, or autonomic nervous system dysfunction.
  • Cardiac arrhythmias: Abnormal heart rhythms can lead to reduced cardiac output, resulting in fainting.
  • Hypoglycemia: Low blood sugar can cause fainting, especially in diabetic patients.
• Do Not Miss diagnoses:
  • Cardiac tamponade: Fluid accumulation in the sac around the heart can compress the heart, leading to reduced cardiac output and fainting.
  • Pulmonary embolism: A blood clot in the lungs can cause sudden fainting due to decreased oxygenation and cardiac output.
  • Aortic dissection: A tear in the aorta can lead to fainting, among other severe symptoms.
  • Severe anemia: Significant blood loss or severe anemia can reduce oxygen delivery to tissues, leading to fainting.
• Rare diagnoses:
  • Subclavian steal syndrome: A rare condition where blood flow is diverted from the brain to the arm, potentially causing fainting.
  • Micturition syncope: Fainting during or after urination, often due to a sudden drop in blood pressure.
  • Defecation syncope: Fainting during or after bowel movements, which can be related to straining or a sudden drop in blood pressure.
  • Glossopharyngeal neuralgia: A rare condition characterized by severe pain in the throat and tongue, which can lead to fainting.