Endocrinol Metab.  2020 Jun;35(2):308-318. 10.3803/EnM.2020.35.2.308.

Subclinical Hypothyroidism Affects the Long-Term Outcomes of Patients Who Undergo Coronary Artery Bypass Grafting Surgery but Not Heart Valve Surgery

• Kim H
• Kong SH
• Moon JH
• Kim SY
• Park KH
• Kim JS
• Choh JH
• Park YJ
• Lim C

• KMID: 2503261
• DOI: http://doi.org/10.3803/EnM.2020.35.2.308

Abstract

Background
The aim of this study was to determine the associations between subclinical hypothyroidism (SCH) and long-term cardiovascular outcomes after coronary artery bypass grafting (CABG) or heart valve surgery (HVS).
Methods
We retrospectively reviewed and compared all-cause mortality, cardiovascular mortality, and cardiovascular events in 461 patients who underwent CABG and 104 patients who underwent HVS.
Results
During a mean±standard deviation follow-up duration of 7.6±3.8 years, there were 187 all-cause deaths, 97 cardiovascular deaths, 127 major adverse cardiovascular events (MACE), 11 myocardial infarctions, one unstable angina, 70 strokes, 30 hospitalizations due to heart failure, 101 atrial fibrillation, and 33 coronary revascularizations. The incidence of all-cause mortality after CABG was significantly higher in patients with SCH (n=36, 55.4%) than in euthyroid patients (n=120, 30.3%), with a hazard ratio of 1.70 (95% confidence interval, 1.10 to 2.63; P=0.018) after adjustment for age, sex, current smoking status, body mass index, underlying diseases, left ventricular dysfunction, and emergency operation. Interestingly, low total triiodothyronine (T3) levels in euthyroid patients who underwent CABG were significantly associated with increased risks of all-cause mortality, cardiovascular mortality, and MACE, but those associations were not observed in HVS patients. Both free thyroxine and thyroid-stimulating hormone levels in euthyroid patients were not related with any cardiovascular outcomes in either the CABG or HVS group.
Conclusion
SCH or low total T3 might be associated with a poor prognosis after CABG, but not after HVS, implying that preoperative thyroid hormonal status may be important in ischemic heart disease patients.

Keyword

Cardiovascular diseases; Heart valve diseases; Cause of death; Prognosis; Hypothyroidism; Thyrotropin; Triiodothyronine

Figure

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  Fig. 1 Kaplan-Meier curves of cardiovascular outcomes in patients with ischemic heart disease. (A) All-cause mortality in subclinical hypothyroidism (SCH) patients over euthyroid patients. (B) Cardiovascular (CV) mortality in SCH patients over euthyroid patients. (C) All-cause mortality according to the total triiodothyronine (T3) tertile in euthyroid patients. (D) Cardiovascular mortality according to the total T3 tertile in euthyroid patients. Cox regression analysis was performed. The hazard ratios (HRs) are for SCH patients with euthyroid patients as references. The HRs are for T3-G1 and T3-G2 patients with T3-G3 as reference. Total T3 tertiles: T3-G1, 0.3 to 83 ng/dL; T3-G2, 85 to 109 ng/dL; T3-G3, 110 to 163 ng/dL. CI, confidence interval.

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