2024 Workshop Handout Bundle-24W02A Autonomic Testing

24W02A Autonomic Testing
Pdf Summary
The document outlines the procedures, indications, and methodologies for conducting autonomic testing, crucial for diagnosing and managing autonomic nervous system disorders. Dr. Phillip A. Low from the Mayo Clinic introduced various non-invasive tests and highlighted the importance of autonomic evaluation, which supplements clinical history and physical exams.<br /><br />### Indications for Laboratory Evaluation of Autonomic Failure<br />1. **Generalized Autonomic Failure:** Condition like multiple system atrophy (MSA), pure autonomic failure (PAF), and autonomic neuropathies (e.g., diabetic autonomic neuropathy).<br />2. **Limited Autonomic Failure Recognition:** Conditions such as syncope, painful feet (distal small fiber neuropathy, DSFN), and postural tachycardia syndrome (POTS).<br />3. **Differentiation of Disorders:** Differentiating benign autonomic disorders that mimic more severe conditions, such as chronic idiopathic anhidrosis and certain syncope cases.<br />4. **Monitoring and Therapy Evaluation:** Assessing the progression of autonomic failure and response to therapy.<br /><br />### Routine Autonomic Function Tests<br />Key routine tests include:<br />1. **Quantitative Sudomotor Axon Reflex Test (QSART):** This measures postganglionic sudomotor function using non-invasive techniques.<br />2. **Heart Rate Response to Deep Breathing (HRDB):** Evaluates cardiovagal function by monitoring heart rate variations during controlled breathing.<br />3. **Valsalva Maneuver:** Tests the autonomic function by measuring heart rate and blood pressure responses to a specific breathing technique.<br />4. **Tilt Table Test:** Examines orthostatic intolerance and autonomic failure by recording BP and HR changes when shifting from a supine to an upright position.<br /><br />### QSART Specifics<br />- **Methodology:** Uses acetylcholine stimulation and measures sweat response via a sudorometer, ideal for studying postganglionic axon function.<br />- **Clinical Relevance:** Helps diagnose distal small fiber neuropathy by testing sweat response at various body sites.<br />- **Gender and Age Influence:** Normative data show variations based on gender and age, affecting test interpretation.<br /><br />### Cardiovagal and Adrenergic Function Tests<br />- **Heart Rate Response to Deep Breathing:** Evaluated by a series of controlled breathing cycles.<br />- **Valsalva Ratio (VR):** Assesses cardiovagal function through heart rate changes during the Valsalva maneuver.<br />- **Beat-to-Beat Blood Pressure (BP) Recording:** Essential for differentiating phase responses in the Valsalva maneuver and tilt-up tests.<br /><br />### Clinical Use and Research Implications<br />Autonomic testing is integral for diagnosing various autonomic disorders, monitoring disease progression, and assessing therapy efficacy. The methodologies and data provided assist clinicians in making informed decisions and advancing medical research in autonomic function.<br /><br />The document also emphasizes patient preparation and equipment requirements for effective autonomic function testing in clinical laboratories.
Keywords
autonomic testing
autonomic nervous system
Dr. Phillip A. Low
Mayo Clinic
autonomic failure
QSART
HRDB
Valsalva maneuver
tilt table test
autonomic disorders