[Mechanism of cough syncope].

Cough induced syncope belongs to the heterogenous group of situational syncopes. The mechanism of tussive syncope is demonstrated by presenting an illustrative case. A 79 year old male with underlying COPD was evaluated because of repeated cough related syncopal episodes. The nature of fainting was elucidated by haemodynamic monitoring of an induced cough attack. As documented by continuous blood pressure and middle cerebral artery blood flow velocity recordings, fainting was the result of the equalization of arterial and central venous pressures, with concomitant decrease in cerebral blood flow. Analogies and differences between haemodynamic responses induced by cough and Valsalva straining are highlighted. The typical lack of prodromal symptoms in cough syncope are well explained by the rapidly developing cerebral hypoperfusion.