Anaphylaxis associated with relative bradycardia

A 31-year-old man with allergic rhinoconjunctivitis and asthma experienced an episode of anaphylaxis following an injection of allergens during hyposensitization. His anaphylactic episode was remarkable because of a relative sinus bradycardia at the beginning of his reaction. This case is reported to highlight the importance of not confusing the anaphylactic syndrome with vasovagal syncope even when a tachycardia is initially absent. The possible pathophysiologic role of right coronary vasospasm resulting in the Bezold-Jarish reflex or sinoatrial node ischemia is discussed.