Elevated thyroid-stimulating hormone is a risk factor in coronary artery bypass grafting

Abstract

Introduction: Asymptomatic hypothyroidism is endemic in most regions of our country. We planned a study to observe the effect of thyroid-stimulating hormone (TSH) in otherwise asymptomatic for hypothyroidism patients, on outcome after coronary artery bypass grafting (CABG). Materials and Methods: This is a retrospective cohort study conducted between January 2017 and December 2019. A total of 449 patients undergoing CABG were included in the study. Patients with redo operations, combined procedures, and emergency operations were excluded from the study. The groups were formed on the level of TSH (normal, subclinical elevation, and clinical elevation) as follows: TSH normal (Group 1, n = 309), TSH subclinical elevation (Group 2, n = 122), and TSH clinical elevation (Group 3, n = 12). One-way ANOVA was used to analyze the groups. Results: There was an increase in the use of inotrope, appearance of atrial fibrillation, and use of intra-aortic balloon pump in Group 3 when compared to that in Groups 1 and 2, P = 0.0001. Higher mortality was observed in group 3 (25%) when compared to group 1 (2.91%) and group 2 (2.45%). There was no difference in the level of free T4, between groups. T3 was similar in TSH normal, TSH subclinical elevation, and clinical elevation group. TSH level of >10 mIU/l predicted mortality with a sensitivity of 91.7% and a specificity of 99.8% in predicting mortality. Conclusion: About 2.67% of the patients undergoing CABG had asymptomatic but clinical elevation of TSH, and it is associated with higher mortality.

Keywords

• coronary artery bypass grafting
• hypothyroidism
• subclinical hypothyroidism