From the Research
Introduction to Autonomic Nervous System Dysfunction
The natural history of cardiovascular and multisystem dysautonomia, also known as Autonomic Nervous System (ANS) dysfunction, is complex and involves various clinical conditions with different characteristics and prognoses 1. Dysautonomia can be classified into several types, including Reflex Syndromes, Postural Orthostatic Tachycardia Syndrome (POTS), Chronic Fatigue Syndrome, Neurogenic Orthostatic Hypotension (nOH), and Carotid Sinus Hypersensitivity Syndrome.
Classification and Characteristics of Dysautonomia
Types of Dysautonomia
- Reflex Syndromes: mostly benign and usually occur in patients without an intrinsic autonomic nervous system (ANS) or heart disease 1
- Postural Orthostatic Tachycardia Syndrome (POTS): characterized by sustained elevation of heart rate in an orthostatic position or during the tilt test, without classical orthostatic hypotension associated 1, 2
- Chronic Fatigue Syndrome: a form of Dysautonomia, also known as a systemic disease of exercise intolerance, with new diagnostic criteria 1
- Neurogenic Orthostatic Hypotension (nOH): a late sign of dysautonomia, defined as a drop in blood pressure upon standing, without hypovolemia or medication-induced causes 1
Natural History and Prognosis
The presence of Cardiovascular Autonomic Neuropathy (CAN) implies greater severity and worse prognosis in various clinical situations 1. Detection of Orthostatic Hypotension (OH) is a late sign and means greater severity in the context of dysautonomia. The natural history of autonomic involvement in hereditary ATTR amyloidosis shows that patients with early-onset disease display autonomic dysfunction more distinctively than those with late-onset disease 3.
Diagnosis and Evaluation
Diagnosis of CAN and the investigation of the involvement of other organs or systems is extremely important in the clinical suspicion of pandysautonomia 1. Valsalva, Respiratory and Orthostatic tests (30:15) are the gold standard methods for the diagnosis of CAN, and can be associated with RR Variability tests to increase sensitivity 1.
Treatment and Management
Treatment of patients at moderate to advanced stages of dysautonomia is quite complex and often refractory, requiring specialized and multidisciplinary evaluation 1. Various drugs can be used for symptomatic nOH, especially fludrocortisone, midodrine, and droxidopa. Preventive measures such as postural care, good hydration, higher salt intake, use of compression stockings and abdominal straps, portioned meals, and supervised physical activity are important treatment steps 1, 2.
Caveats and Considerations
- The risk of exacerbation or triggering supine hypertension should be considered when treating nOH patients 1
- The Tilt Test should not be the test of choice for investigating CAN at an early stage, as it detects cases at more advanced stages 1
- Polypharmacy may be required to control symptoms associated with postural orthostatic tachycardia syndrome 2
Conclusion
In conclusion, the natural history of cardiovascular and multisystem dysautonomia is complex and involves various clinical conditions with different characteristics and prognoses. Early diagnosis and evaluation are crucial to prevent progression and improve outcomes. Treatment and management require a multidisciplinary approach, and various drugs and preventive measures can be used to control symptoms and prevent complications 1, 2, 3, 4, 5.