Definition and Overview
Post-stroke autonomic dysfunction is a condition in which extensive abnormalities in autonomic function occur due to direct invasion of the central autonomic network (CAN) due to cerebrovascular damage or indirect neurohumoral changes.
Approximately 60-80% of stroke patients are accompanied by at least one type of autonomic dysfunction, which independently affects mortality, cardiovascular complications, and functional outcome in the acute phase of stroke.
Brain-Heart Axis
Central autonomic network
The insular cortex, anterior cingulate cortex, amygdala, hypothalamus, and brainstem autonomic nuclei (nucleus medullaris sulcus nucleus, etc.) constitute the central autonomic network. This network comprehensively regulates cardiovascular, respiratory, digestive, sweating, and pupillary reactions.
Left and right lateralization of the insula
In a study by Oppenheimer et al., it was found that stimulation of the right insula caused a sympathetic response (increased heart rate, increased blood pressure), and stimulation of the left insula caused a parasympathetic response (decreased heart rate). Therefore, right insular stroke may result in increased sympathetic activity and increased risk of arrhythmia, and left insular stroke may result in changes in parasympathetic activity.
Catecholamine hypersecretion
In acute stroke, especially extensive infarction of the cerebral hemisphere or cerebral hemorrhage, blood catecholamines (epinephrine, norepinephrine) rapidly increase due to hyperactivation of the hypothalamic-sympathetic-adrenomedullary axis. This causes myocardial damage (neurogenic stunned myocardium), arrhythmia, and acute heart failure.
cardiovascular autonomic disorder
cardiac arrhythmia
Electrocardiogram abnormalities are observed in approximately 25% of acute stroke patients. QT prolongation, ST changes, T wave inversion, atrial fibrillation, and ventricular tachycardia are reported, and are particularly frequent in insular lobe involvement.
Heart rate variability (HRV) changes
After stroke, HRV significantly decreases, reflecting a decline in autonomic control of the heart. In a meta-analysis, HRV decline was identified as an independent predictor of mortality after stroke.
- Decreased SDNN: Decreased overall autonomic modulation ability.
- RMSSD, reduced HF: decreased parasympathetic function.
- Increased LF/HF ratio: sympathetic dominance
Orthostatic hypotension
Poststroke orthostatic hypotension is observed in approximately 35-50% of patients in the acute phase, and is caused by a combination of deconditioning caused by long-term bed rest and autonomic dysreflexia. Orthostatic hypotension is a major barrier to early rehabilitation and increases the risk of falls.
Increased blood pressure variability
After stroke, a non-dipping pattern in which 24-hour blood pressure variability increases and nocturnal blood pressure drop (dipping) disappears is common. Increased blood pressure variability is a risk factor for stroke recurrence and cardiovascular events.
Non-cardiovascular autonomic disorders
abnormal sweating
Unilateral hemihyperhidrosis or anhidrosis on the ipsilateral or contralateral side of the stroke lesion may occur. More common in hypothalamic or brainstem injuries.
Digestive autonomic disorder
Gastroparesis and constipation due to decreased intestinal motility are common after stroke. It is an important factor in managing nutritional status along with dysphagia.
bladder dysfunction
Bladder dysfunction after stroke is reported in approximately 40-60% of cases, with urge incontinence being the most common. It is caused by damage to the urinary center of the pons or loss of inhibitory function in the cerebral cortex.
Temperature regulation disorder
Central fever may occur when the hypothalamus is damaged, and fever after a stroke is a factor that worsens brain damage and requires active fever relief.
diagnosis
Cardiovascular autonomic assessment
- Continuous electrocardiogram monitoring (telemetry): acute arrhythmia surveillance
- 24-hour ambulatory blood pressure measurement (ABPM): assessment of blood pressure variability and nocturnal dipping
- HRV analysis: quantitative assessment of autonomic control ability
- Orthostatic blood pressure test: Screening for orthostatic hypotension
Comprehensive autonomic nervous system examination
From the subacute phase to the recovery period, a battery of autonomic tests including Valsalva maneuver, cardiorespiratory heart rate variability, standing tilt test, and QSART are performed to evaluate the extent and severity of functional impairment.
Treatment and Management
Acute Cardiovascular Care
- Continuous electrocardiogram monitoring (recommended at least 72 hours)
- Beware of drugs that cause QT prolongation
- Management of blood pressure volatility (preventing sudden drops in blood pressure)
Orthostatic hypotension management
- Progressive head-up tilt training
- Wear elastic stockings and belly band
- Intake of sufficient water (2-2.5 L/day) and salt (6-10 g/day)
- Medications: midodrine, fludrocortisone — as needed
Consideration of autonomic nerves in the rehabilitation process
Rehabilitation exercise programs should be designed considering the state of autonomic function. In patients with orthostatic hypotension, strategies such as gradually increasing the tilt angle and contracting lower limb muscles before standing are applied. Regular aerobic exercise has been reported to improve HRV and contribute to restoring autonomic balance.
long term tracking
Since autonomic dysfunction after stroke is a risk factor for recurrence of cardiovascular events, regular HRV monitoring and blood pressure management are necessary in the long term. Track the recovery of autonomic function and adjust the treatment plan.