Impact of subclinical hypothyroidism on clinical outcomes following percutaneous coronary intervention ☆ Yonggu Lee a , Young-Hyo Lim b, ⁎, Jeong-Hun Shin b , Jinkyu Park b , Jinho Shin b a Division of Cardiology, Department of Internal Medicine, Hanyang University Guri Hospital, Guri City, Kyunggi-do, Republic of Korea b Division of Cardiology, Department of Internal Medicine, College of Medicine, Hanyang University, Seoul, Republic of Korea abstract article info Article history: Received 1 December 2016 Received in revised form 31 May 2017 Accepted 22 September 2017 Background: Similar to overt hypothyroidism, subclinical hypothyroidism (SCH) has been reported to increase the risk of cardiovascular disease. However, the influence of SCH on clinical outcomes following percutaneous coronary intervention (PCI) remains unclear. Methods: We performed a prospective cohort study. SCH was defined as a thyroid-stimulating hormone (TSH) level ≥ 4.5 mIU/l and a normal level of free thyroxine (FT4). A composite event was defined as the combination of cardiac death, non-fatal myocardial infarction (MI) and repeat revascularization. Results: Of 936 patients, who were observed for 3.1 years, 100 patients (10.7%) were diagnosed with SCH. Repeat revascularization, cardiac death and a composite event occurred more frequently in the SCH group than in the euthyroidism group, while the incidence of non-fatal MI was similar between the two groups. Multiple Cox regression analysis showed that SCH was associated with the risk of a composite event (hazard ratio, 1.52; 95% confidence interval, 1.04–2.22) after adjustment for age, sex, current smoking, ST-segment elevation MI, prior PCI, diabetes, hypertension, renal function, left ventricular ejection fraction, B-type natriuretic peptide, stent numbers, total stent length, stent types, obesity and lipid profiles. Serum TSH levels were also significantly associated with the risk of a composite event. SCH was not associated with repeat PCIs for de novo stenotic lesions but was associated with repeated PCIs for in-stent restenotic lesions. Conclusions: SCH negatively impacted clinical outcomes following PCIs. Therefore, patients with SCH should be carefully observed after undergoing a PCI. © 2017 Elsevier B.V. All rights reserved. Keywords: Subclinical hypothyroidism Percutaneous coronary intervention Clinical outcomes 1. Introduction Subclinical hypothyroidism (SCH) is a common clinical condition with a prevalence of 4–20% in the general population. SCH presents with few or no symptoms or signs of hypothyroidism but features a slightly elevated serum thyroid-stimulating hormone (TSH) level [1,2]. Although the serum levels of free thyroxine (FT4), the active hormone, are typically within the reference range, several studies have reported increased cardiovascular risk and mortality in SCH patients [3,4]. Sub- clinical atherosclerotic disorders, such as coronary artery calcification, carotid intima-media thickening and atheroma, are more prevalent in SCH [5,6]. Endothelial dysfunction, impaired cholesterol metabolism and increased C-reactive protein (CRP) levels have also been reported to be associated with SCH [7–9] and to affect clinical outcomes following percutaneous coronary interventions (PCIs). However, whether SCH is associated with cardiovascular events and death in patients undergoing PCIs remains uncertain [10]. Therefore, we investigated the differences in clinical outcomes following PCIs between patients with normal TSH levels and patients with SCH in a prospective clinical cohort study. 2. Methods 2.1. Patients A prospective PCI registry has been operated in the Department of Cardiology, Hanyang University Hospital, Seoul, Republic of Korea since 2009 to evaluate the clinical outcomes and safety of PCIs [11]. Patients undergoing coronary angiography in the center were consecutively enrolled in the registry. Written informed consent was obtained from all patients before enrollment. The Hanyang University Hospital Institutional Review Board approved the protocol and monitored registry operation. Patients in the registry who underwent PCI with simple balloon angioplasty or stent implantation between March 2010 and December 2013 were consecutively enrolled in this study. Patients who had previously undergone coronary artery bypass surgery were excluded, as were patients who suffered from debilitating conditions including advanced malignancies, advanced liver cirrhosis, severe autoimmune diseases and cerebrovascular accidents with major sequelae. Information regarding demographic characteristics, past medical histories and social histories was obtained. Body weights, heights, and waist circumferences were determined on the day before or within 7 days after index PCI. Lipid profiles, serum glucose levels and hemoglobin A1c levels were measured after an 8-h fast the morning before or following the index PCI. Serum highly sensitive CRP International Journal of Cardiology 253 (2018) 155–160 ☆ All authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation. ⁎ Corresponding author at: Division of Cardiology, Department of Internal Medicine, Hanyang University College of Medicine, 222 Wangsipri Street, Sung-dong-gu, Seoul 133-792, South Korea. E-mail address: mdoim@hanyang.ac.kr (Y.-H. Lim). https://doi.org/10.1016/j.ijcard.2017.09.192 0167-5273/© 2017 Elsevier B.V. All rights reserved. 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