Impact of subclinical hypothyroidism on outcomes of coronary bypass surgery

Background Subclinical hypothyroidism (SCH) is characterized by an elevated thyroid-stimulating hormone and normal free thyroxine. This study aimed to evaluate the influence of SCH on the recovery of patients after coronary artery bypass grafting (CABG). Methods From January 2015 to December 2018, 548 SCH patients and 6718 euthyroid patients who underwent CABG were identified. Propensity score matching was used to create two cohorts with similar baseline characteristics (n = 545 in each group). The early postoperative outcomes were compared. Results After CABG, there was no difference in the incidence of postoperative atrial fibrillation between the two groups (20.4% in the SCH group and 20.6% in the euthyroidism group; odds ratio: 0.99; 95% confidence interval: 0.74-1.33; p = 0.94). Subgroup analyses did not indicate an effect in any category of patients. The proportions of the use of dopamine and noradrenaline in the SCH group were higher than those in the euthyroid patients (76.7% vs. 68.6%, p = 0.003; 56.5% vs. 49.0%, p = 0.01, respectively). The total duration of inotropic support in the SCH group was longer than that in the euthyroid patients (median duration: 4 vs. 3 days, p = 0.002). The incidence of impaired wound healing was higher in the SCH group than in the euthyroid group (3.7% vs. 1.1%, p = 0.005). Conclusions Compared with euthyroidism, SCH is not associated with an increased risk of atrial fibrillation in patients undergoing CABG. It is associated with an increased risk of several minor perioperative problems, which should be anticipated and preemptively managed.