Histamine, paroxysmal AV block and low adenosine syncope a case report

Histamine is a widespread natural amine, rarely suspected to provoke syncope due to complete atrio-ventricular block. A patient was admitted to the emergency room after an episode of vomiting and syncope following a dinner of mussels, most likely attributable to a histamine food intoxication. Stale mussels are ostensibly known to occasionally encompass high concentrations of histamine. We hereby present, a documented unexpected complete atrioventricular block (AV block) with preserved stable sinus electrical activity during an episode of fainting with vomiting. Pathophysiologically, we hypothesize a possible intense H1 and/or A1 receptor stimulation linked to histamine overload, suggestive of a variant of idiopathic AVB or low adenosine syncope.