Thyrotoxicosis-induced congestive heart failure in an urban hospital.

Thyrotoxicosis has been associated with several cardiac complications, including atrial fibrillation (AF), functional cardiomyopathy, and congestive heart failure (CHF). Thyrotoxicosis-induced CHF has been considered an unusual complication of thyrotoxicosis, occurring generally in older patients. To determine the nature and frequency of this complication of thyrotoxicosis in an adult, hospitalized population, the authors consecutively evaluated all admissions to a 535-bed urban hospital during a 14-month period. Admitted during the study period were 177 individuals with a principal diagnosis of AF and 21 individuals with a principal diagnosis of thyrotoxicosis. Eleven of these individuals had concomitant AF and thyrotoxicosis, which was 6% of the AF group. Of these 11 patients, 5 had clinically apparent CHF without evidence of other organic heart disease (Group A) and 6 had only AF without clinical CHF (Group B). The 5 patients with CHF had a significantly lower mean age (36) than the 6 with thyrotoxicosis and AF only (P < 0.03). Echocardiography revealed Group A to have a mean of 2.8 cardiac chambers enlarged compared with a mean of 1 in Group B (P < 0.008). Four of the five patients with CHF had normal left ventricular function. Mean levels of serum thyroxine, albumin, hematocrit, left ventricular percent shortening, and left atrial diameter were similar in groups A and B. Based on the authors' data, thyrotoxicosis-induced CHF is not as rare a complication of thyrotoxicosis in young individuals as reported previously. Thyrotoxicosis-induced CHF most commonly has a dilated cardiomyopathy and high output failure.