MON-610 Different Effects of Subclinical Hypothyroidism on Long-Term Outcomes of Patients Underwent CABG and Heart Valve Surgery

We performed this study to investigate whether subclinical hypothyroidism (SCH) is associated with long-term cardiovascular outcome after coronary artery bypass grafting (CABG) or heart valve surgery (HVS). All-cause mortality and cardiovascular (CV) mortality, and cardiovascular events were retrospectively reviewed in 395 euthyroid and 66 SCH patients who underwent CABG. We also analyzed cardiovascular outcomes in 87 euthyroid and 17 SCH patients who underwent HVS. During a mean follow-up period of 7.5 ± 3.9 years, there were 159 incidents of all-cause deaths, 26 CV deaths, 124 major cardiovascular adverse events (MACE), 11 myocardial infarctions, 1 unstable angina, 70 strokes, 23 hospitalizations due to heart failure, 101 atrial fibrillation events, and 33 coronary revascularizations. The incidence rate of all-cause mortality after CABG was significantly higher in patients with SCH (n=31, 47.0%) than in euthyroid patients (n=105, 26.6%), with a hazard ratio (HR) of 1.721 (95% confidence interval [CI] 1.068, 2.772; p=0.026) after adjustment with age, sex, underlying diseases, LV dysfunction and emergency operation. Interestingly, low T3 level in euthyroid patients (TSH 0.0-4.0mIU/L) who underwent CABG significantly increased all-cause, CV mortality and MACE in contrast to those of HVS. Moreover, both low T4 and high TSH level in euthyroid patients (TSH 0.0-4.0mIU/L) were not related to increased all-cause mortality, CV mortality and MACE in both CABG and HVS groups. In conclusion, insufficient thyroid status including low T3 in euthyroid and subclinical hypothyroid is associated with a long-term mortality in patients who underwent CABG, but the effects were not observed in HVS suggesting the importance of preoperative thyroid hormonal status in patients with ischemic heart disease. More RCTs should be needed to confirm whether normalization of thyroid function before CABG operation is helpful for the better postoperative outcome.