Reversible hypocalcaemic cardiomyopathy following post-thyroidectomy hypoparathyroidism: a case report.

Background: Hypocalcaemic cardiomyopathy is a rare but reversible cause of dilated cardiomyopathy (DCM) and heart failure with reduced ejection fraction, commonly associated with post-operative hypoparathyroidism. Misdiagnosis as other forms of cardiomyopathy can delay appropriate treatment and worsen outcomes. Case summary: A 36-year-old male presented with progressive dyspnoea, abdominal pain, and peripheral oedema. He had a history of invasive thyroid carcinoma treated with total thyroidectomy and radioactive iodine therapy, complicated by permanent hypoparathyroidism. Despite sustained alcohol abstinence, he was misdiagnosed with alcoholic cardiomyopathy and experienced recurrent hospitalizations for heart failure despite guideline-directed medical therapy (GDMT). Evaluation revealed severe hypocalcaemia, prolonged QTc (557 ms), and echocardiographic findings of DCM with a left ventricular ejection fraction (LVEF) of 28%. Hypocalcaemic cardiomyopathy secondary to post-thyroidectomy hypoparathyroidism was diagnosed. Calcium and calcitriol supplementation, combined with GDMT, led to significant improvement. At 10 months, the patient's LVEF improved to 52%, QTc normalized to 397 ms, and symptoms resolved completely. He was transitioned to endocrinology for long-term management. Discussion: Hypocalcaemic cardiomyopathy should be suspected in unexplained DCM with a history of hypoparathyroidism. Timely calcium testing and correction, along with GDMT, can reverse cardiac dysfunction and improve outcomes.