What is dysautonomia and how is it diagnosed and treated?

Dysautonomia: Diagnosis and Management

Dysautonomia refers to dysfunction of the autonomic nervous system that can manifest as abnormal functioning of multiple organ systems, with symptoms affecting heart rate, blood pressure, digestion, and other autonomic functions. 1

Definition and Classification

Dysautonomia encompasses a broad spectrum of autonomic disorders characterized by dysfunction of the autonomic nervous system (ANS). It can be:

• Primary/Idiopathic: Such as pure autonomic failure or multisystemic atrophy
• Secondary: Due to underlying conditions like diabetes mellitus, neurodegenerative diseases, Parkinson's disease, chronic renal failure, or amyloidosis 2

Common clinical presentations include:

1. Postural Orthostatic Tachycardia Syndrome (POTS): Characterized by sustained heart rate elevation ≥30 bpm (≥40 bpm if <20 years) or HR ≥120 bpm within 10 minutes of standing, without classical orthostatic hypotension 2, 3

2. Neurogenic Orthostatic Hypotension (nOH): A late sign indicating greater severity of dysautonomia 2

3. Cardiovascular Autonomic Neuropathy (CAN): Impairment of sympathetic and/or parasympathetic cardiovascular autonomic nervous system 2

4. Chronic Fatigue Syndrome: Characterized by unexplained fatigue leading to occupational disability for >6 months, post-exertional malaise, non-restorative sleep, and cognitive impairment or orthostatic intolerance 2

Diagnostic Approach

Diagnosis of dysautonomia requires a systematic approach:

Clinical Evaluation

• Assessment of orthostatic symptoms (dizziness, lightheadedness, weakness)
• Evaluation of other dysautonomic symptoms (palpitations, exercise intolerance, cognitive dysfunction, fatigue) 4
• Identification of potential underlying causes (diabetes, autoimmune disorders)

Diagnostic Testing

1. Cardiovascular Autonomic Reflex Tests (CARTs):

   • Valsalva maneuver
   • Respiratory tests
   • Orthostatic tests (30:15 ratio)
   • These are considered gold standard for diagnosing CAN 2

2. Heart Rate Variability (HRV) Tests:

   • Time domain and frequency domain analyses to increase sensitivity
   • Can detect subclinical abnormalities 2

3. In-office 10-minute stand test or tilt table test:

   • Monitors heart rate and blood pressure changes with position 4, 5
   • A dysautonomic pattern shows gradual blood pressure drop without compensatory heart rate increase 2

4. Monitoring of heart rate and blood pressure:

   • With changes in position and respiration
   • Can demonstrate sympathetic withdrawal and cholinergic aspects 5

Management Approach

Treatment of dysautonomia focuses on symptom management and improving quality of life:

Non-Pharmacological Interventions (First-Line)

• Postural care: Avoiding prolonged standing, rising slowly from sitting/lying positions
• Adequate hydration: 2-2.5 liters of fluid daily 6
• Increased salt intake: To maintain blood volume 6, 2
• Compression garments: Stockings and abdominal straps 6, 2
• Physical activity: Supervised exercise, preferably sitting, lying down, or in water 2
• Head-up tilt sleeping (>10°): For patients with supine hypertension 6
• Physical counterpressure maneuvers: To combat orthostatic symptoms 6

Pharmacological Management

For orthostatic hypotension, first-line medications include:

1. Midodrine:

   • FDA-approved peripheral selective α1-adrenergic agonist
   • Increases vascular tone and elevates blood pressure
   • Standing systolic BP elevated by 15-30 mmHg at 1 hour after 10 mg dose 7
   • Side effects may include hypertension, piloerection, sensation of coldness, and urinary retention 7

2. Fludrocortisone:

   • Used for volume expansion
   • Individual titration to 0.1-0.3 mg daily 6
   • Side effects include hypertension, edema, cardiac enlargement, potassium loss 8

3. Droxidopa:

   • FDA-approved for orthostatic hypotension 6
   • Not available in all countries 2

For POTS, additional medications may include:

• Beta blockers
• Ivabradine
• Pyridostigmine
• Stimulants 4

Special Considerations

Supine Hypertension

• Over 50% of patients with neurogenic orthostatic hypotension develop supine hypertension 2
• Management priorities:
  • Immediate risks of orthostatic hypotension take precedence over later risks of supine hypertension
  • BP values up to 160/90 mmHg may be tolerable 2
  • Short-acting antihypertensives (losartan, captopril, clonidine) may be used for severe cases 2

Comorbid Conditions

• In diabetic patients, 38-44% can develop dysautonomia with prognostic implications 2
• Progression typically affects parasympathetic system first, then sympathetic system, and finally presents as orthostatic hypotension 2

Pitfalls to Avoid

1. Misdiagnosis: Dysautonomia is often misdiagnosed as psychiatric disorders 4
2. Medication effects: All medications should be reevaluated as they may reveal or exacerbate subclinical dysautonomia 2
3. Delayed diagnosis: Significant delays in diagnosis can lead to development of chronic syndromes 5
4. Overlooking comorbidities: Dysautonomia is a common comorbidity of systemic diseases 4

Remember that while there is no cure for most types of dysautonomia at late stages, proper management can significantly improve quality of life and reduce morbidity 2, 9.