Impact of Hypothyroidism on Short-Term and Long-Term Outcomes of Coronary Artery Bypass Graft Surgery

BACKGROUND: Thyroid dysfunction has been associated with adverse postoperative outcomes, but little is known about its effects on patients undergoing coronary artery bypass grafting (CABG). Here, our goals were (1) to evaluate the incidence of CABG in patients with hypothyroidism receiving thyroid hormone replacement therapy, and (2) to assess short-term and long-term outcomes in patients with hypothyroidism undergoing CABG compared with controls without thyroid disease, and (3) to determine whether abnormal preoperative thyroid-stimulating hormone (TSH) levels modify postoperative surgical risk in this patient population.

METHODS: Retrospective longitudinal study using the TriNetX Global Collaborative Network database. The incidence of CABG was evaluated in about 1.23 million patients with hypothyroidism during a 20-year observation period (median of 4.4 ± 5.9). Post-CABG outcomes, including mortality, cardiovascular events, and postsurgical complications, were evaluated in 6557 patients with hypothyroidism over 10 years after 1:1 propensity score-matching.

RESULTS: Over 20 years, patients with a diagnosis of hypothyroidism had a higher incidence of CABG compared with controls (0.27% vs. 0.22%; hazard ratio [HR] 1.08; confidence interval [CI]: 1.03-1.14). Among patients who underwent CABG, the diagnosis of hypothyroidism was associated with mild increased risk of short-term postsurgical infections (HR:1.10, CI:1.01-1.20), CABG-specific complications (HR: 1.24, CI: 1.08-1.42), and critical care utilization (HR:1.14, CI:1.07-1.21). During long-term follow-up, these patients were at increased risk of incident heart failure (HR:1.15, CI:1.04-1.28), stroke (HR:1.18, CI:1.01-1.39), and major adverse cardiovascular events (MACE) (HR:1.15, CI:1.01-1.29). Sensitivity analysis, including only patients with hypothyroidism diagnosis, showed that abnormal preoperative TSH levels, particularly those with elevated TSH, had a higher risk of short-term mortality and long-term embolic events.

CONCLUSIONS: Hypothyroidism is associated with a higher incidence of coronary disease requiring CABG and increased risks of postoperative complications, heart failure, stroke, and MACE. These findings support the potential value of preoperative thyroid function assessment and optimization to mitigate postoperative complications and improve surgical outcomes in this high-risk group.