Mid-term outcomes of patients with subclinical hypothyroidism after coronary bypass surgery

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 mid-term outcomes of patients after coronary artery bypass grafting (CABG).

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 2 cohorts with similar baseline characteristics (n = 544 in each group). The mid-term follow-up outcomes were compared. Adjusted hazard ratios (HRs) were calculated using Cox proportional hazards models.

The mean follow-up for all patients was 39.7 ± 17.3 months. The unadjusted Kaplan-Meier estimate for mortality at 5-year follow-up was higher in patients with SCH compared with euthyroid patients (5.3% vs 1.6%, log-rank P = 0.03). After adjusting for covariates, the risk of mortality was higher in patients with SCH compared with euthyroid patients [HR, 2.40; 95% confidence interval (CI), 1.03-5.58; P = 0.04]. The adjusted risk of major adverse cardiovascular and cerebral event (HR, 2.16; 95% CI, 1.51-3.08; P < 0.001) and angina (HR, 2.44; 95% CI, 1.41-4.24; P = 0.001) was higher in patients with SCH compared with euthyroid patients.

SCH is associated with an increased risk of mortality, major adverse cardiovascular and cerebral event and angina compared with euthyroidism in patients undergoing CABG.