Unusually high serum levels of lactate dehydrogenase without perivalvular leakage following double valve replacement: predictor of tetany attack after thyroidectomy.

A 57-year-old woman who complained of exertional dyspnea was diagnosed as having severe aortic valve stenosis and mitral valve regurgitation. The patient underwent double valve replacement with a mechanical prosthesis. Postoperative laboratory data showed unusually high serum lactate dehydrogenase (LDH) levels, even though no perivalvular leakage was detected by echocardiography. Tetany occurred suddenly owing to hypoparathyroidism, which seemed to be a late complication after thyroidectomy. After calcium administration, the symptoms dramatically diminished, as did the serum LDH levels. Hypoparathyroidism should be doubted if serum LDH levels increase higher than the normal range following valve replacement without obvious perivalvular leakage.