What does the ANS regulate?
- HR
- BP
- Breathing
- Digestion
- Temperature control
Branches of ANS
- Sympathetic nervous system
- Parasympathetic nervous system
Sympathetic nervous system actions
- Peripheral vasoconstriction (increases BP)
- Increased HR and contractility
- Bronchodilation
- Pupil dilation
- Mobilises glucose and releases adrenaline
- Decreases GI motility and salivation
- Relaxes bladder
Parasympathetic nervous system action
- Vasodilation
- Decreases HR and contractility
- Pupil constriction
- Stimulates digestion and GI motility
- Increases salivation
- Constricts bladder
- Assists ventilation patterns
What does AFT evaluate?
Healthy body maintains a balance between sympathetic and parasympathetic activity. AFT evaluates this
Why test ANS?
Autonomic dysfunction affects multiple organ systems long before symptoms become severe
Reasons for testing ANS
- Early detection of ANS imbalance
- Prevent progression to neuropathy
- Stratify risk for future syncopal episodes
- Guide diagnosis and therapy
- Preserve pt QoL and longevity
Progression of autonomic dysfunction
- Autonomic dysfunction
- Peripheral autonomic neuropathy
- Diabetic autonomic neuropathy
- Cardiovascular autonomic neuropathy
- Higher risk of sudden cardiac death
When is AFT useful (terms of syncope assessment)
- Unexplained syncope or pre-syncope
- Orthostatic intolerance
- POTS
- OH
- Delayed OH
- Differentiating neural mediated syncope from cardiac causes
Purpose of AFT
To non-invasively evaluate:
- Distribution and severity of autonomic dysfunction
- Parasympathetic and sympathetic responses
- BP and HR patterns during physiological stress tests
Sympathetic tests
- Hand grip test
- Short valsalva manoeuvre
- Postural change
- Cold water test
- Sweat response testing
Parasympathetic tests
- Deep breathing test
- Long valsalva manoeuvre
- Postural change
Deep Breathing test purpose
Assess cardiac vagal control
Physiological basis of deep breathing
- Inspiration = decreases vagal tone; increases HR
- Expiration = increases vagal tone; decreases HR
What does the deep breathing tests measure?
- Vagal modulation of HR
- Integrity of parasympathetic pathways
Reduced HR variability suggests? (deep breathing test)
- Early autonomic dysfunction
- Diabetic autonomic neuropathy
- CV autonomic neuropathy
Purpose of active standing test
- Orthostatic response
- Evaluates physiological responses when moving from lying to standing
Why is active standing test important?
Standing requires:
- Rapid sympathetic activation
- Peripheral vasoconstriction
- HR rise to maintain cerebral perfusion
What is the valsalva manoeuvre?
Forced expiration against a closed glottis for ~10-15 seconds
What does valsalva manoeuvre test?
- Sympathetic adrenergic function
- Parasympathetic cardiovagal function
- Integrity of baroreceptor reflexes
Interpretation of AFT results (what doe they help classify)
- Parasympathetic dysfunction
- Sympathetic dysfunction
- Mixed autonomic neuropathies
