Thyroid hormones have many effects on the heart and vascular system. Although 
cardiac output is reduced in hypothyroidism, heart failure is relatively rare 
because there is a lower demand for peripheral oxygen delivery. Hypothyroidism 
may also result in accelerated atherosclerosis and coronary artery disease. We 
report the case of a 55-year-old man with severe heart failure associated with 
severe longstanding untreated hypothyroidism. The patient was admitted for 
shortness of breath and chest pain. On presentation, signs and symptoms of 
severe hypothyroidism and heart failure were noticed. The electrocardiogram 
showed sinus bradycardia and ischemia. Thyroid stimulating hormone was extremely 
elevated and thyroid hormone levels were undetectable. A cardiac ultrasonography 
exam revealed abnormalities of the left ventricular dimensions and function 
consistent with dilated cardiomyopathy. Coronary angiography showed severe 
multivessel disease. Coronary by-pass was deemed necessary, but surgery was 
postponed because of severe heart failure. After an increasingly downhill 
clinical course, the patient died, eight month after his initial presentation, 
owing to severe heart failure. This patient represents an example of an 
overlooked diagnosis of severe hypothyroidism, rarely encountered nowadays, 
leading to dramatic consequences.