Prolonged persistence of a large pericardial effusion and hemodynamic evidence of cardiac tamponade during treatment of myxedema.

We describe clinical, echocardiographic, and catheterization findings that were present initially and during therapy in a myxedematous patient with a large pericardial effusion and tamponade. Treatment with thyroxine resulted in a marked improvement of most of the clinical features of hypothyroidism and some improvement in cardiac function. However, the pericardial effusion as well as clinical and laboratory evidence of tamponade persisted for 2 months after full replacement doses of T4 had been achieved. The tamponade was finally relieved by fenestration of the parietal pericardium. These findings are consistent with evidence of an abnormality of pericardial drainage that persists for months after other thyroid hormone dependent functions are normalized by thyroxine replacement. Therefore prompt surgical drainage rather than dependence on medical therapy alone is indicated in myxedematous patients who have cardiac tamponade.