Stop the Heart to Live: The Fascinating Origin of The Neurocardiogenic Syncope.

Neurocardiogenic syncope (NCS) is traditionally considered a benign yet perplexing condition, characterized by transient loss of consciousness due to reflex bradycardia and hypotension. Why would Nature create a reflex that stops the heartbeat, risking collapse, injury, or even death? Our observations, based on Cardioneuroablation and high number of NCS patients, suggest that this reflex may have evolved as a primitive survival mechanism probably to mitigate blood loss during hemorrhage improving the survival likelihood in primitive cold-blooded aquatic animals. Over millions of years, this reflex has persisted as a vestigial trait, despite significant physiological changes in modern homeothermic organisms. 2 This review examines how this condition evolved from an aneural heart to the modern autonomic nervous system, with particular emphasis on the vagus nerve's development and its role from early vertebrates. It discusses the transition from cold-blooded to warm-blooded life forms, highlighting how changes in metabolic demands and circulatory regulation have rendered the once-beneficial cardioinhibitory reflex into a maladaptive in present-day humans.