The heart brain axis

This narrative review examines why patients with total artificial hearts (TAHs) and left ventricular assist devices (LVADs) retain their memories and sense of self, and argues that identity is stored in distributed brain networks, not in the heart. It reviews the evidence on heart-to-brain communication (vagal afferents, baroreceptor pulse-phase signalling, heartbeat-evoked potentials, humoral pathways) and critically evaluates popular claims about a "heart brain" and cardiac electromagnetic entrainment. It identifies the genuinely open question: whether reduced pulsatility under mechanical circulatory support alters the intensity of emotional experience, for which direct evidence is currently lacking. It proposes the Archive–Modulator framework, with five falsifiable predictions, in which the brain stores identity and cardiac signals modulate, but are not required for, emotion. Finally, it outlines a prospective study design, including a within-patient pump-setting sub-study, to confirm or refute a modulatory role of cardiac pulsatility.Keywords: neurocardiology; interoception; heart–brain axis; total artificial heart; left ventricular assist device; emotion; heartbeat-evoked potential; pulsatility