Incidence of Subclinical Hypothyroidism in Cardiac Surgery Patients. Comparison of Presentation Characteristics, Hospital and Medium-Term Outcomes with Euthyroid Patients

Subclinical hypothyroidism (SCHT) is common, with an occurrence of up to 10% of the adult population and defined biochemically only by elevated TSH and normal T4. SCHT affects negatively on lipid and carbohydrate metabolism increasing the risk of ischemic heart disease, affects negatively on cardiac performance and have a close correlation with renal function. The aim of this study is to compare presentation characteristics and outcomes between euthyroid pts and pts with SCHT who underwent cardiac surgery. Methods: 474 pts from June 2003 through September 2004 had TSH and T4 measured. 365 pts were euthyroid (Group 1), 41 pts had SCHT (Group 2). Groups were compared by demographics and EuroSCORE (ES) risk profiles. Operative and hospital outcomes were compared as was follow-up mortality up to 96 months. Results: There were more females in Group 2, p = 0.04, more pts with CHF and number of NYHA III-IV pts (p < 0.05). More pts in Group 2 had elevated s-crea (p < 0.0001) and atrial fibrillation (p = 0.007). Comparing the Groups by EuroSCORE (ES) showed higher risk scores in Group 2 pts (Additive ES 6.8 vs 8.5 and Logistic ES 12.3% vs 18.1%, p = 0.01 and 0.03). Hospital mortality was higher in Group 2 (12.2% vs 4.1%, p = 0.04) and the number of pts needing extended care was higher in Group 2 (p = 0.01). Follow up mortality was doubled in Group 2 pts up to 96 months compared to Group 1 (p < 0.0001). Conclusions: Presentation characteristics and risk scores are different and worse in SCHT pts compared with euthyroid pts. Hospital and follow-up mortality are increased in SCHT pts.