Abstract
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.
Highlights
After observing a remarkable degree of overlooking and undertreatment of hypothyroid patients admitted for cardiac surgery a decision was made to have thyroid screening (TSH and T4) of every pt admitted for cardiac surgery in our unit
Subclinical hypothyroidism (SCHT) has many negative effects on different bodily functions: it decreases cardiac performance by decreasing both systolic and diastolic function increasing the risk of congestive heart failure (CHF) [2], it increases systemic vascular resistance and lowers preload [1,3], it has negative effect on lipid metabolism increasing the risk of accelerated general and cardiac atherosclerosis with subsequent increased risk to develop ischemic heart disease [1,3,4] and long-term mortality
Comparing demographic data reveals statistically significant differences in number of females (p = 0.04, Odds ratios (ORs) 2.19, 95%CI 1.07 - 4.46) in pts with congestive heart failure (CHF) (p = 0.02, OR 2.21, 95%CI 1.17 - 4.47), in pts with atrial fibrillation (AF) (p = 0.007, OR 4.11, 95%CI 1.56 - 10.85), NYHA class (p = 0.0006) number of NYHA III-IV pts (p = 0.005), pts with high s-creatinine levels (p < 0.0001, OR 1.46, 95%CI 1.23 - 1.73)
Summary
After observing a remarkable degree of overlooking and undertreatment of hypothyroid patients (pts) admitted for cardiac surgery a decision was made to have thyroid screening (TSH and T4) of every pt admitted for cardiac surgery in our unit. Subclinical hypothyroidism (SCHT) is a common occurrence in the adult population, affecting 4% - 10% of the population [1]. It is defined biochemically only and pts with TSH over the upper reference limit and T4 within the normal range are diagnosed having SCHT. Increased mortality has recently been reported in pts with heart disease and SCHT [5]. Thyroid disorders and diabetes mellitus influence each other and diabetes is observed more in SCHT and hypothyroid pts which further increases risk of ischemic heart disease [10]
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