Hypomagnesaemia causing functional hypoparathyroidism in rheumatic mitral stenosis leading to sudden cardiac arrest in a young woman

A 23-year-old young woman with a known history of valvular heart disease of rheumatic origin, post balloon mitral valvotomy 5 years ago, presented with fever, palpitations and breathlessness. ECG showed atrial fibrillation with fast ventricular rate. A 2D transthoracic echocardiography showed severe restenosis of mitral valve and moderate left ventricular dysfunction. She was admitted for evaluation of fever and control of the ventricular rate. She sustained cardiac arrest due to unknown cause and was resuscitated. When the patient sustained another cardiac arrest, torsades de pointes was detected on the monitor. Blood parameters showed hypomagnesaemia, hypocalcaemia and hypokalaemia, causing functional hypoparathyroidism which was treated with intravenous magnesium, oral calcium and vitamin D supplements. Timely detection of a tachyarrhythmia due to a ventricular origin was life saving, which is rarely seen in patients with rheumatic heart disease and mitral stenosis.