Hyponatraemia-induced Takotsubo syndrome secondary to idiopathic syndrome of inappropriate antidiuretic hormone: a case report

Background: Takotsubo cardiomyopathy (TC), also known as stress cardiomyopathy or broken-heart syndrome, is an acute, reversible left ventricular dysfunction often triggered by stress and associated with elevated catecholamine levels. Hyponatraemia has been recognized as a potential trigger for TC, although its pathophysiological mechanisms remain unclear. Case summary: We present the case of an 84-year-old woman with a history of Type 2 diabetes, primary hypertension, hypothyroidism, and osteoporosis, who was admitted for typical angina and seizures. Initial laboratory tests revealed severe hyponatraemia (serum sodium: 119 mmol/L) and elevated cardiac enzymes. Electrocardiogram showed Wellens Type B syndrome and subsequent ST-segment elevation. Coronary angiography revealed no significant coronary lesions. Optical coherence tomography showed a non-significant lesion in the anterior descending artery, and ventriculography confirmed TC. The patient was treated with beta-blockers and managed for syndrome of inappropriate antidiuretic hormone-induced hyponatraemia with fluid restriction. Follow-up echocardiography at three months showed recovery of global longitudinal strain and preserved biventricular systolic function. Cardiac magnetic resonance imaging demonstrated normal chamber dimensions and late gadolinium enhancement with a non-ischaemic pattern. Discussion: This case underscores the association between severe hyponatraemia and TC, highlighting the need for careful electrolyte management in patients with acute cardiac symptoms. The exact mechanisms linking hyponatraemia and TC remain to be elucidated, but this case contributes to the limited literature on hyponatraemia-induced TC, emphasizing the importance of recognizing and addressing this electrolyte imbalance to prevent cardiac complications.