Does thyroid dysfunction affect early mortality and morbidity after coronary artery bypass graft surgery?

Objectives: This study aims to evaluate to effect of thyroid dysfunction on early mortality and morbidity in patients undergoing coronary artery bypass grafting (CABG). Patients and methods: Between April 2008 and December 2010, a total of 37 patients (20 females, 17 males; mean age 54.9±10.2 years; range, 26 to 76 years) with thyroid dysfunctions who underwent CABG and 11 patients (2 females, 9 males; mean age 46.9±15.5 years; range, 26 to 65 years) without thyroid dysfunction who underwent on-pump CABG as the control group were included in the study. Patients were divided into groups as overt and subclinical hypothyroidism, overt hyperthyroidism, and subclinical hyperthyroidism according to the thyroid function test results. The European System for Cardiac Operative Risk Evaluation (EuroSCORE) scores were evaluated and the Gensini severity scores were calculated according to coronary angiographies. All patients were followed for seven days after surgery. The duration of endotracheal intubation, inotropic support, cardiac complications, duration of stay in the intensive care unit (ICU) and hospital were recorded. Results: There were no statistically significant differences between the groups in terms of the duration of intubation, need of inotropic support, and duration of stay in the ICU and hospital. Arrhythmia was more frequent in the overt hyperthyroid group than in the overt hypothyroid group postoperatively. Thyroid-stimulating hormone (TSH) levels remained unchanged after surgery, whereas free T3 decreased and free T4 increased, which was compatible with postoperative euthyroid sick syndrome. The EuroSCORE scores were positively correlated with pre- and postoperative TSH levels, duration of intubation, and duration of ICU and hospital stay, but was negatively correlated with free T3. Conclusion: Subclinical or overt thyroid dysfunctions do not seem to affect early mortality after CABG. However, overt hyperthyroidism is associated with postoperative arrhythmia complications. Euthyroid sick syndrome may also occur after surgery in certain cases. Pre- and postoperative TSH and free T3 levels may be useful to identify mortality and morbidity risk in patients undergoing CABG.