From the Guidelines
Brain injury can lead to cardiac complications through the neurocardiac axis, which is the bidirectional communication pathway between the brain and heart, and management typically involves treating the underlying brain injury while monitoring cardiac function through regular ECGs and cardiac enzyme measurements. When the brain is injured, it can disrupt normal autonomic nervous system function, causing an imbalance between sympathetic and parasympathetic activity. This typically manifests as a surge in sympathetic activity, leading to the release of catecholamines like epinephrine and norepinephrine, which can cause cardiac issues such as arrhythmias, myocardial dysfunction, and electrocardiogram abnormalities, as seen in a study published in the Annals of Surgery in 2017 1. Common cardiac complications following brain injury include:
- QT interval prolongation
- ST-segment changes
- T-wave inversions
- Takotsubo cardiomyopathy (stress-induced cardiomyopathy) In severe cases, beta-blockers like metoprolol (starting at 25-50mg twice daily) may be used to counteract excessive sympathetic stimulation, as suggested by a guideline published in Stroke in 2021 1. The hypothalamus, insular cortex, and brainstem are key brain regions involved in cardiac regulation, and damage to these areas particularly increases the risk of cardiac complications. Understanding this neurocardiac connection is essential for comprehensive care of brain-injured patients, as cardiac complications can significantly impact recovery outcomes, and continuous ECG and cardiac monitoring for at least the first 24 hours are needed, as recommended by a scientific statement from the American Heart Association published in Stroke in 2021 1. Additionally, a study published in Stroke in 2015 found that serious cardiac events and cardiac death after stroke may be caused by acute myocardial infarction, heart failure, ventricular arrhythmias, and cardiac arrest, highlighting the importance of monitoring and managing cardiac complications in patients with brain injury 1.
From the Research
Neurocardiac Axis Overview
The neurocardiac axis refers to the complex relationship between the brain and the heart, where brain injury or dysfunction can lead to cardiac complications, and vice versa. This relationship is bidirectional, meaning that brain injury can affect the heart, and heart problems can also impact the brain.
Brain Injury and Cardiac Complications
- Brain injury, such as traumatic brain injury (TBI) or non-traumatic brain injury (NT-BI), can lead to cardiac complications, including cardiac dysfunction, arrhythmias, and increased cardiac biomarkers 2, 3, 4.
- The mechanisms of injury in hypoxic-ischemic encephalopathy, which can occur after cardiac arrest, involve impaired circulation and molecular basis of injury, leading to brain damage and potential cardiac complications 5.
- Cardiac arrest survivors often suffer from ischemic brain injury, and understanding the mechanisms of injury is essential for providing effective therapies for brain protection 5.
Cardiovascular Events in Brain Injury
- Brain injury in children can lead to cardiovascular events, including neurogenic stunned cardiomyopathy, which presents as alterations in blood pressure, cardiac rhythm disturbances, and increased cardiac injury biomarkers 3.
- Both hypotension and hypertension are associated with worse outcomes in brain-injured patients, and early evaluation of arterial pressure, electrocardiographic, and echocardiographic assessment can be critical in identifying poor prognostic factors 3.
Prognostic Markers and Mortality
- Elevated serum cardiac troponin (cTn) is associated with a higher mortality in patients with TBI or NT-BI, with an overall pooled odd ratio (OR) of 3.37 (95% CI 2.13-5.36) 4.
- Cardiac dysfunction is common in patients with moderate-severe TBI and is independently associated with more severe brain injury and a reduction in hospital survival 2.