Cardiothyreosis: Prevalence and risk factors

Cardiothyreosis (CT) or thyrotoxic heart disease is associated with higher morbidity and mortality than the other forms of hyperthyroidism. Its risk factors have been analyzed in a limited number of studies. The aims of our study were to investigate the prevalence of CT and its risk factors in patients with hyperthyroidism.

We identified 538 patients with a hospital discharge diagnosis of hyperthyroidism from January 2000 to December 2015. Among them, 35 patients were diagnosed as having CT. Their demographic, clinical and biological characteristics were studied and compared with those of 72 controls (patients admitted for hyperthyroidism without CT) randomly selected using univariate and multivariate analysis.

The prevalence of CT in patients hospitalized with overt hyperthyroidism was 6.5%. The cardiac complications seen were atrial fibrillation (AF) in 33 cases (6.1%) and cardiac heart failure (CHF) in 11 cases (2%). The risk factors of CT were age greater than 50 years (OR=13.1; 95% CI [4.9-34.4]), low socioeconomic status (OR=2.8; 95% CI [1.2-6.7]), low educational level (OR=3.1; 95% CI [1.2-8.3]), personal history of hypertension (OR=3.5; 95% CI [1.1-11.2]) and a multinodular toxic goiter as the etiology of hyperthyroidism (OR=4.6; 95% CI [1.6-13.9]). After multivariate analysis, age greater than 50 years was the only independent risk factor of CT (adjusted OR=11.6; 95% CI [2.7-49.5]). Severe biological hyperthyroidism (FT4 >3 times normal) was associated with a lower risk of CT (adjusted OR=0.2; 95% CI [0.1-0.9]).

The prevalence of CT in patients with overt hyperthyroidism was relatively low. Cardiac complications were AF and CHF with a clear predominance of AF. Advanced age was the only independent risk factor of CT. Cardiac complications may be seen even if hyperthyroidism is not biologically severe.