Effect of Low T3 Syndrome on Severity of Coronary Artery Disease in Patients with Acute Coronary Syndrome: A Cross-sectional Study

Abstract

Introduction: Low Triiodothyronine (T3) syndrome is a hormonal imbalance that significantly influences cardiovascular haemodynamics by altering the vascular endothelial function by influencing the Nitric Oxide (NO) production. In Acute Coronary Syndrome (ACS) inflammation disrupts plaque which stimulates thrombosis, coagulation, activation of sympathetic system and release of cytokines mainly Interleukin 6 (IL-6), which is a pleotropic and pro-inflammatory cytokine, which exerts inhibitory effect on thyroid axis function. Aim: To study the association of low T3 syndrome and severity of Coronary Artery Disease (CAD) in ACS. Materials and Methods: This cross-sectional study was conducted in the Intensive Critical Care Unit (ICCU)under the Department of Cardiology, Karnataka institute of Medical Sciences, Hubli, Karnataka, India, from July 2021 to August 2022. A total of 120 consecutive ACS patients were taken for the study and all underwent Coronary Angiography (CAG). Severity of CAD was assessed with the help of Gensini risk scoring system. The patients were divided based on thyroid function status. Low T3 syndrome was defined as <0.846 ng/ mL with normal values of Thyroxine (T4) and Thyroid Stimulating Hormone (TSH). Receiver operating characteristic curves were generated to correlate low T3 syndrome and angiographic severity of CAD. Multinominal logistic regression analysis demonstrated LT3S is an independent risk factor for CAD. The Chi-square test was used for ordered categorical data with the severity of coronary artery lesions. Results: The severity of coronary artery lesions in the low T3 syndrome group (n=29, 24.16%) and hypothyroidism (n=20, 16.6%) group was significantly greater than that of euthyroid group (n=71, 59.1%), with all the groups’ (p-value=0.047). Multinominal logistic regression analysis demonstrated that low T3 syndrome was an independent risk factor of CAD for moderate (Odds ratio=2.34, 95%CI: 0.47-11.39, p<0.02) and severe (Odds ratio=8.56, 95%CI: 1.52-47.9, p<0.015) lesions. Conclusion: The patients with low T3 syndrome are associated with more severe and diffuse CAD and low T3 syndrome is an independent risk factor for ACS.