Differential Diagnosis for Syncopal Episode on Toilet

• Single most likely diagnosis:
  • Defecation syncope: This condition is caused by the sudden increase in abdominal pressure during defecation, leading to a vagal response and subsequent decrease in heart rate and blood pressure, resulting in syncope. The fact that the episode occurred on the toilet makes this diagnosis highly plausible.
• Other Likely diagnoses:
  • Vasovagal syncope: A common cause of fainting spells, often triggered by stress, pain, or prolonged standing. The strain of defecation could potentially trigger a vasovagal response.
  • Orthostatic hypotension: A drop in blood pressure upon standing, which could be exacerbated by the physical strain of defecation or dehydration.
  • Cardiac arrhythmias: Certain arrhythmias, such as atrial fibrillation or ventricular tachycardia, could lead to a syncopal episode, especially if the heart is unable to maintain adequate cardiac output during physical strain.
• Do Not Miss diagnoses:
  • Myocardial infarction (MI) or acute coronary syndrome: Although less common, a syncopal episode could be a presenting symptom of an MI, especially in older adults or those with cardiovascular risk factors.
  • Pulmonary embolism (PE): A life-threatening condition that could cause syncope due to a sudden blockage of a pulmonary artery, potentially triggered by the physical strain of defecation.
  • Aortic dissection: A rare but deadly condition where the inner layer of the aorta tears, potentially causing syncope, severe chest pain, or other symptoms.
• Rare diagnoses:
  • Carotid sinus syncope: A rare condition where pressure on the carotid sinus causes a reflexive decrease in heart rate and blood pressure, leading to syncope.
  • Subclavian steal syndrome: A rare condition where there is a reversal of blood flow in the subclavian artery, potentially causing syncope or other neurological symptoms.
  • Tussive syncope: Although more commonly associated with coughing, the physical strain of defecation could potentially trigger a similar response in rare cases.