Abstract 15661: Impairment of Thyroid Function in Patients With Fontan Circulation
Background: An increase in central venous pressure (CVP) and decrease in cardiac output (CI) in Fontan circulation may have adverse effects on thyroid function due to congestion and low perfusion of the thyroid gland. Because thyroid hormones play important roles in the regulation of the cardiovascular system, thyroid dysfunction may be involved in the pathophysiology of Fontan circulation. We investigated the pathophysiological relationships between Fontan hemodynamics and thyroid function.
Methods and Results: Thirty-seven consecutive patients who had undergone a Fontan operation (median year after the surgery: 4.2 years) had cardiac catheterization and blood tests for thyroid function. One patient treated with amiodarone was excluded from the analysis. Of these, 9 patients (25%) had subclinical thyroid dysfunction defined as elevated thyroid stimulating hormone (TSH) level, but normal thyroid hormone levels. The levels of TSH were significantly correlated with CVP (P<0.01, R2=0.3), and patients with subclinical hypothyroidism showed significantly elevated levels of gamma-glutamyl transferase, an indicator of liver congestion, compared to the remaining patients (125.6±12.2 vs. 67.6±4.6 IU/L, P<0.01), suggesting the importance of venous congestion as a cause of subclinical hypothyroidism. Although levels of free triiodothyronine (fT3), an effective thyroid hormone, were generally within the normal range, fT3 levels in the subclinical hypothyroidism group were significantly lower than those in the normal thyroid function group (3.1±0.1 vs. 3.5±0.1 pg/dmLl, P<0.01). Furthermore, fT3 was significantly and negatively correlated with relaxation time constant (P=0.03) and brain natriuretic hormone (P<0.01), and positively correlated with CI (P=0.04).
Conclusion: Venous congestion in Fontan patients may cause thyroid dysfunction, and impaired thyroid function can be responsible for decreased ventricular function and cardiac output in Fontan patients. These novel findings suggest that thyroid function should be routinely monitored after Fontan surgery, and that thyroid hormone replacement therapy may be an effective treatment option to improve Fontan hemodynamics.
Author Disclosures: S. Kuwata: None. C. Kurishima: None. A. Yana: None. Y. Iwamoto: None. H. Saiki: None. H. Ishido: None. S. Masutani: None. H. Senzaki: None.
- © 2016 by American Heart Association, Inc.