In situational syncope, which trigger is classic?

• A. Coughing, defecation, or urination
• B. Standing up quickly
• C. Exercise
• D. Postprandial

Answer: (A)

Situational syncope is a vasovagal-type faint triggered by a specific activity that provokes a reflex causing sudden bradycardia and vasodilation, leading to transient cerebral hypoperfusion. The classic triggers are coughing, defecation, or urination because these activities involve intense Valsalva-like straining and autonomic reflexes that abruptly change heart rate and vascular tone. This combination readily tips susceptible individuals into a brief loss of consciousness.

Standing up quickly can cause orthostatic hypotension from sudden venous pooling, which is a different mechanism. Exercise generally increases sympathetic tone and venous return, making fainting less likely during activity. Postprandial fainting can occur from postprandial hypotension, but it’s not the classic situational trigger pattern described here.