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Hyponatremia in heart failure — RCPSC IM MCQ

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HardCardiologyHyponatremia in heart failureRCPSC IM

A 79-year-old woman with heart failure with reduced ejection fraction is admitted with edema and dyspnea. Sodium is 124 mmol/L, serum osmolality is low, urine osmolality is 510 mOsm/kg, urine sodium is 12 mmol/L, and JVP is elevated. Creatinine is 144 umol/L and she has bibasal crackles. What is the most likely cause?

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Correct answer: B — Non-osmotic vasopressin release from low effective arterial blood volume

Hypervolemic hypotonic hyponatremia in decompensated heart failure reflects low effective arterial volume, which stimulates vasopressin despite total body fluid excess. The low urine sodium supports avid renal sodium retention.

Reference: Canadian Cardiovascular Society heart failure guidance