Influence of Mild Thyroid Dysfunction on Outcomes after Off-Pump Coronary Artery Bypass Surgery

We retrospectively evaluated the association between preoperative mild thyroid dysfunction (subclinical hypothyroidism [SCH] or low triiodothyronine [T3] syndrome) and outcomes in patients who underwent off-pump coronary surgery (OPCAB). Further, 800 patients (2015–2020) were divided into euthyroid, low T3, and SCH groups. The primary outcome assessed the association with composite endpoints (myocardial infarction, prolonged mechanical ventilation [>24 h], acute kidney injury, and 30-day/in-hospital mortality). The secondary outcome assessed the association with long-term mortality and 10% and 8% of the patients exhibited low T3 and SCH, respectively. Incidences of composite endpoints were significantly higher in the low T3 and SCH groups versus the euthyroid group (50.6%, 45.2%, 17.4%, respectively, p < 0.001). Multivariable regression analysis revealed chronic kidney disease, anemia, EuroSCORE, low T3, and SCH as independent risk factors of composite endpoints. The long-term mortality rate (median follow-up, 30 months) was higher in the low T3 and SCH groups than in the euthyroid group (9.6%, 11.3%, 2.4%, respectively, p < 0.001). In the absence of overt thyroid dysfunction, low T3 and SCH were associated with increased risk of adverse outcomes after OPCAB. Moreover, the adverse influences of low T3 and SCH seem to extend to long-term mortality, implying that routine thyroid function tests may enhance accurate risk stratification.