A patient develops orthostatic hypotension with preserved heart rate response (no reflex tachycardia) upon standing. This pattern is most consistent with:
- A Efferent sympathetic failure (pure autonomic failure) affecting both cardiac and vascular sympathetic output ✓
- B Volume depletion with intact baroreceptor reflex
- C Parasympathetic failure selectively impairing vagal withdrawal
- D Afferent baroreceptor failure with intact efferent sympathetic function
Explanation
Normally, upon standing, baroreceptor unloading triggers reflex sympathetic activation: efferent sympathetic fibers simultaneously increase heart rate (via cardiac sympathetics) and increase peripheral vascular resistance (via vasoconstrictor sympathetics), maintaining blood pressure. In pure autonomic failure (PAF) or multiple system atrophy, there is widespread efferent sympathetic dysfunction — both vasoconstriction and cardiac acceleration responses are lost, causing orthostatic hypotension WITHOUT compensatory tachycardia. In volume depletion, the baroreceptor reflex is intact, so a reflex tachycardia occurs with orthostatic hypotension. Afferent baroreceptor failure would impair reflex responses but produce different hemodynamic patterns.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.