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

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