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Hyponatraemia in HF — EECC MCQ

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ModerateHeart FailureHyponatraemia in HFEECC

A 58-year-old man with HFrEF (LVEF 28%) presents with a serum sodium of 126 mmol/L. He is congested (oedematous, elevated JVP, pulmonary crackles). What does the hyponatraemia indicate?

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Correct answer: A — Hyponatraemia in HF is a marker of neurohormonal activation severity (excessive ADH/vasopressin secretion) and is independently associated with poor prognosis

Hyponatraemia in HF (typically dilutional, occurring in 20-25% of acute HF admissions) is caused by non-osmotic release of arginine vasopressin (ADH) driven by: reduced effective circulating volume (perceived by baroreceptors), RAAS activation, and sympathetic activation. This leads to free water retention disproportionate to sodium retention, producing dilutional hyponatraemia. It is a strong independent predictor of adverse outcomes (in-hospital mortality, 30-day readmission, 1-year mortality). Management focuses on decongestion (IV diuretics), fluid restriction (if Na⁺ <130 mmol/L), and treatment of the underlying HF. Tolvaptan (V2 receptor antagonist) may be considered for resistant hyponatraemia (Class IIb). Hypertonic saline is rarely needed and risks fluid overload.

Reference: ESC (2023): HF Guidelines