Autonomic Neurology Differential Diagnosis Hemodynamic Cutoffs

Pure Autonomic Failure (PAF) vs. POTS vs. Neurally Mediated Hypotension

Autonomic disorders can look identical to the untrained eye: standing dizziness, fainting, brain fog, and exhaustion. This clinical diagnostic monograph provides the exact hemodynamic cutoffs, plasma norepinephrine levels, and tilt-table signatures to differentiate Pure Autonomic Failure from POTS and Neurally Mediated Hypotension (NMH).

1. Clinical Comparison Matrix

Parameter POTS Pure Autonomic Failure (PAF) Neurally Mediated Hypotension (NMH)
Standing Heart Rate Increases ≥ 30 bpm (exceeds 120 bpm) Fixed / Blunted increase (< 10 bpm) Normal initially, then sudden bradycardia
Standing Blood Pressure Stable or elevated (hyperadrenergic) Severe immediate drop (≥ 30/15 mmHg) Stable, then precipitous drop before collapse
Supine Norepinephrine Normal to elevated (> 600 pg/mL upright) Extremely low (< 100 pg/mL) Normal at baseline
Primary Pathology Hypovolemia, small-fiber denervation Alpha-synuclein Lewy body pathology Bezold-Jarisch paradoxical reflex

Peer-Reviewed References

  1. Kaufmann H, et al. Pure autonomic failure: a disorder of alpha-synuclein. Lancet Neurol. 2017;16(8):634-645. PMID: 28721927.
  2. Sheldon RS, et al. 2015 Heart Rhythm Society Expert Consensus Statement on POTS, IST, and VVS. Heart Rhythm. 2015;12(6):e41-63. PMID: 25980514.
  3. Rowe PC, et al. The relation between chronic fatigue syndrome and neurally mediated hypotension. JAMA. 1995;274(12):961-967. PMID: 7674527.