Subclinical Hypothyroidism and Coronary Revascularization After Coronary Artery Bypass Grafting

Area of Science:

• Cardiology
• Endocrinology
• Cardiovascular Surgery

Background:

• Subclinical hypothyroidism (SCH) is a condition characterized by elevated thyroid-stimulating hormone levels with normal free thyroxine and triiodothyronine.
• The long-term cardiovascular implications of SCH following major cardiac surgery, such as coronary artery bypass grafting (CABG), remain incompletely understood.

Purpose of the Study:

• To investigate the association between preoperative subclinical hypothyroidism and long-term cardiovascular outcomes in patients undergoing coronary artery bypass grafting.
• To identify specific cardiovascular sequelae and risk factors in patients with SCH post-CABG.

Main Methods:

• Retrospective review of 258 patients (222 euthyroid, 36 SCH) who underwent CABG.
• Analysis of all-cause and cardiovascular-related mortality, and major adverse cardiovascular events over an average follow-up of 8.2 years.
• Statistical adjustment for potential confounders and subgroup analysis for postoperative atrial fibrillation (AF).

Main Results:

• Patients with SCH had a significantly higher incidence of coronary revascularization (16.6% vs. 9.0%) compared to euthyroid patients (HR 3.179, p=0.023).
• SCH patients with postoperative AF within 3 months showed a markedly increased risk of coronary revascularization (HR 11.759, p=0.001).
• The frequency of unstable angina was also significantly higher in SCH patients (12.5% vs. 2.5%, HR 16.999, p=0.006).

Conclusions:

• Preoperative subclinical hypothyroidism is linked to poorer long-term cardiovascular outcomes after CABG, notably an increased need for coronary revascularization.
• Postoperative atrial fibrillation in SCH patients exacerbates the risk of unstable angina and subsequent revascularization.
• Preoperative thyroid function assessment may aid in predicting long-term prognosis following CABG.