Cardiac status after prolonged thyrotoxicosis

Abstract

This is a clinical study aimed at ascertaining the amount of cardiac damage produced by hyperthyroidism. Since it is generally agreed that duration of the thyrotoxicosis, rather than its intensity, is the important factor in causing heart impairment, only cases of prolonged thyrotoxicosis are included here. The cases of twenty patients known to have been toxic for six months to eleven years were studied. Only one of these may be considered a cardiac cripple, and this patient had evidence of circulatory failure antedating the onset of thyrotoxicosis by four years. Two other patients (aged fifty and fifty-five years) had hypertension, which, from their histories could not be ascribed to their thyroid disease. There was no correlation between duration (or intensity) of thyrotoxicosis and heart size, blood pressure etc. It was concluded that when cardiac failure supervened in the course of thyrotoxicosis it was a temporary functional insufficiency resulting from overwork (prolonged tachycardia, increased blood flow etc.), since there remained no evidence of permanent organic damage and because there is no characteristic pathological lesion. Further evidence in support of this view is that thyroid-cardiac disease is seldom, if ever, found in young people, but only in those in the later decades of life who have had their cardiac reserve already encroached upon by degenerative cardiovascular changes.