[A case of myxedema with diffuse myocardial fibrosis proven by endomyocardial biopsy]

We report a middle-aged woman with myxedema heart who presented both clinical features resembling dilated cardiomyopathy and the diffuse myocardial fibrosis proven by endomyocardial biopsy. Thirty years previously, when she was 36 years old, partial thyroidectomy had been performed after a diagnosis of hyperthyroidism was made. Four years later, she experienced dry skin and peripheral edema, and hypothyroidism was diagnosed. Several months after, replacement therapy for hypothyroidism improved her symptoms. However, the therapy was discontinued because of her ignorance of the disease. Twenty six years later (64 years old), she felt exertional dyspnea, and was admitted to Fukuoka University Hospital for evaluation of her cardiac state. Thyroid function test revealed primary hypothyroidism with low T3, low T4 and high TSH levels. Cardiothoracic ratio on chest X-ray film was 69%. Electrocardiogram showed low voltage in the limb leads and intraventricular conduction disturbance. Echocardiogram demonstrated marked dilatation and severely reduced wall motion of the left ventricle and pericardial effusion. Left ventriculogram showed diffuse hypokinesis with 27% of the ejection fraction. No significant stenosis was observed on coronary arteriogram. Seventeen-month replacement therapy did not improve these cardiac findings significantly. Transvenous right ventricular endomyocardial biopsy demonstrated diffuse myocardial fibrosis without inflammatory infiltrate, which was interpreted as a sequel of interstitial lesions of the myxedema heart such as edema or mucoid infiltration. This pathological finding suggests that long-standing untreated hypothyroidism can cause irreversible myocardial damage.