Autonomic nervous system function in chronic hypotension associated with Bartter and Gitelman syndromes

Area of Science:

• Nephrology
• Cardiology
• Neurology

Background:

• Autonomic nervous system (ANS) dysfunction is linked to blood pressure (BP) drops in orthostatic hypotension and syncope.
• Bartter and Gitelman syndromes feature reduced extracellular fluid volume and hypotension, but ANS status in these patients is unexplored.

Observation:

• This study assessed sympathetic and parasympathetic nervous system function in four patients with Bartter and Gitelman syndromes and chronic hypotension.
• Autonomic reflex tests included responses to orthostatism, Valsalva maneuver, cold-pressor test, hand-grip test, and deep breathing, with continuous BP monitoring.
• Plasma catecholamines were measured, revealing increased norepinephrine concentrations during standing in patients.

Findings:

• One patient exhibited orthostatic hypotension and syncope, yet overall ANS function remained intact across all tested individuals.
• Valsalva ratios, BP responses to cold pressor and hand-grip tests, and heart rate variations during deep breathing were within normal limits.
• Despite chronic hypotension and occasional syncope, patients demonstrated preserved sympathetic and parasympathetic nervous system function.

Implications:

• Chronic hypotension in Bartter and Gitelman syndromes appears unrelated to ANS dysfunction, even with orthostatic intolerance.
• The findings suggest alternative pathophysiological mechanisms, potentially involving abnormal vasoconstrictor cell signaling, underlie hypotension in these syndromes.
• Further research into non-autonomic pathways is warranted to understand and manage hypotension in Bartter and Gitelman syndromes.