Takotsubo syndrome induced by severe hyponatraemia in mineralocorticoid-responsive hyponatraemia of the elderly: a case report.

Background: There are limited reports on mineralocorticoid-responsive hyponatraemia of the elderly (MRHE), a condition that can cause severe hyponatraemia. Case summary: An 85-year-old woman presented with transient loss of consciousness and nausea likely due to untreated severe hyponatraemia (114 mEq/L). Thirty-nine hours after initial admission, she developed sudden cardiac dysfunction and entered a circulatory collapse state. The patient was diagnosed with Takotsubo syndrome. Her hyponatraemia was an essential feature of syndrome of inappropriate antidiuretic hormone secretion. However, she was clinically hypovolaemic. Therefore, the hyponatraemia was diagnosed as MRHE. The serum sodium level was corrected with 3% hypertonic saline administered at a rate of 10 mL per hour, with careful monitoring to avoid overly rapid correction and prevent osmotic demyelination. After 14 days, her serum sodium level, electrocardiogram findings, and cardiac contractions on echocardiography improved. Discussion: To our knowledge, this is the first documented case of Takotsubo syndrome induced by severe hyponatraemia resulting from MRHE. The present report shows that acute cardiomyopathy can develop when severe hyponatraemia is not treated within several hours and at least a day. Since patients with MRHE are hypovolaemia statement, avoidance of diuretic drugs and water restriction for the treatment of hyponatraemia should be carefully considered, especially if they have acute cardiac dysfunction. This report highlights the need for prompt management of severe hyponatraemia in elderly patients and calls for further research on MRHE treatment protocols and its link to cardiomyopathy.