This chapter explores the mechanisms and clinical implications of brain-heart crosstalk in acute brain injury (ABI) patients, particularly in the context of intensive care. Brain-heart interactions manifest through various pathophysiological phenomena, including Takotsubo cardiomyopathy after subarachnoid hemorrhage (SAH), paroxysmal sympathetic hyperactivity following traumatic brain injury (TBI), and cardiac anomalies after acute ischemic stroke (AIS). These interactions result in a spectrum of cardiac dysfunction, characterized by arrhythmias, cardiomyocyte injury, and echocardiographic changes. The severity of cardiac dysfunction correlates with poor neurological outcomes, emphasizing the prognostic significance of monitoring cardiac markers in ABI patients. Despite the known implications of brain-heart axis dysfunction, management largely remains conservative, prompting the need for further research to clarify treatment strategies. This synthesis aims to summarize the mechanisms of brain-heart communication and evaluate their clinical relevance across ABI types, ultimately highlighting the necessity for improved understanding and intervention in critically ill patients.