Heart-brain axis pathophysiological understanding and clinical impact.

The heart and brain are anatomically and functionally interconnected through nervous and humoral feedback mechanisms. Under physiological conditions, the heart-brain axis helps maintain cardiovascular and cerebral homeostasis. Pathology affecting one organ can profoundly impact the other, significantly worsening prognosis. The term stroke-heart syndrome refers to cardiovascular complications following acute ischemic stroke, including myocardial injury, infarction, ventricular dysfunction, arrhythmias (e.g., atrial fibrillation), heart failure, takotsubo syndrome, and sudden cardiac death. Brain damage-induced cardiac injury arises from a complex interplay of neuroinflammation, systemic immune activation, sympathetic-immune interactions, catecholamine toxicity, endothelial dysfunction, and gut-brain-heart axis involvement. Conversely, cardiac conditions, including myocardial ischemia, heart failure, and atrial fibrillation, are associated with an increased risk of stroke and cognitive decline. Myocardial ischemia can initiate systemic inflammation and neuroinflammation through sympathetic overdrive and platelet activation. Heart failure causes cerebral hypoperfusion and high thromboembolic risk, and atrial fibrillation promotes thrombus formation due to blood stasis. Atrial dysfunction and prothrombotic states may also occur independently of arrhythmia. This review summarises current evidence on the pathological interactions within the heart-brain axis, in the context of stroke, mental stress, ischemic heart disease, heart failure, and atrial fibrillation.