From the Guidelines
Autonomic dysfunction, also known as dysautonomia, refers to a condition where the autonomic nervous system (ANS) doesn't work properly, leading to symptoms such as orthostatic hypotension, rapid heartbeat, and fatigue, as seen in conditions like Classical OH, which is associated with increased mortality and cardiovascular disease prevalence 1.
Definition and Symptoms
Autonomic dysfunction encompasses a range of symptoms due to the ANS's failure to regulate involuntary bodily functions correctly. This includes heart rate, blood pressure regulation, as evidenced by orthostatic hypotension (OH) syndromes like Classical OH, Initial OH, and Delayed OH, which are characterized by different timelines and pathophysiologies of blood pressure response to standing 1. Symptoms can also include exercise intolerance, gastrointestinal issues, and abnormal sweating.
Pathophysiology and Diagnosis
The pathophysiology behind autonomic dysfunction involves the impairment of autonomic nerves that control various bodily functions. In the context of orthostatic hypotension, this can lead to a sustained decrease in systolic blood pressure >20 mmHg or diastolic blood pressure >10 mmHg within 3 minutes of standing, as defined in Classical OH 1. Diagnosis often involves tests like the active standing test or tilt-table test to assess blood pressure and heart rate responses to standing.
Treatment and Management
Treatment of autonomic dysfunction focuses on managing symptoms and may include lifestyle modifications such as increasing salt and fluid intake, wearing compression stockings, and performing physical counter-maneuvers when feeling faint. Medications can be prescribed based on specific symptoms; for example, fludrocortisone to increase blood volume, midodrine to constrict blood vessels, or beta-blockers like propranolol to manage heart rate 1. The choice of treatment should be guided by the underlying cause of the autonomic dysfunction and the specific symptoms presented, prioritizing interventions that improve morbidity, mortality, and quality of life.
Underlying Conditions
Autonomic dysfunction can result from various underlying conditions, including diabetes, autoimmune disorders, or neurological diseases like Parkinson's. Identifying and managing these underlying conditions is crucial in the treatment of autonomic dysfunction. Given the potential for increased mortality and cardiovascular disease prevalence associated with conditions like Classical OH, early diagnosis and aggressive management are warranted 1.
From the Research
Definition and Causes of Automatic Dysfunction
- Automatic dysfunction, also known as autonomic dysfunction, refers to a condition where the autonomic nervous system is impaired, leading to various symptoms involving the cardiovascular, gastrointestinal, and urogenital systems 2.
- The autonomic nervous system is designed to maintain physiologic homeostasis, and its widespread connections make it vulnerable to disruption by many disease processes, including primary etiologies such as Parkinson's disease, multiple system atrophy, dementia with Lewy bodies, and pure autonomic failure 2.
- Secondary etiologies, such as diabetes mellitus, amyloidosis, and immune-mediated illnesses, can also cause autonomic dysfunction 2.
Symptoms and Diagnosis of Automatic Dysfunction
- Patients with autonomic dysfunction often have peripheral and/or cardiac denervation leading to impairment of the baroreflex, which plays a major role in determining hemodynamic outcome during orthostatic stress and low cardiac output states 2.
- Heart rate and plasma norepinephrine responses to orthostatic stress are helpful in diagnosing impairment of the baroreflex in patients with orthostatic hypotension and suspected autonomic dysfunction 2.
- Cardiac sympathetic denervation diagnosed with MIBG scintigraphy or 18F-DA PET scanning has also been shown to be helpful in distinguishing preganglionic from postganglionic involvement and in diagnosing early stages of neurodegenerative diseases 2.
Treatment and Management of Automatic Dysfunction
- Management of orthostatic hypotension, a common symptom of autonomic dysfunction, is aimed at improving quality of life and reducing symptoms rather than at normalizing blood pressure 3.
- Nonpharmacologic measures are the key to success, and pharmacologic options include volume expansion with fludrocortisone and sympathetic enhancement with midodrine, droxidopa, and norepinephrine reuptake inhibitors 3.
- Atomoxetine, a norepinephrine transporter blocker, has been shown to be effective in improving upright blood pressure and orthostatic hypotension-related symptoms in patients with severe autonomic failure 4.