Impact of subclinical hypothyroidism on clinical outcomes following percutaneous coronary intervention

Abstract

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/1 and a normal level of free thyroxine (FT4). A composite event was defined as the combination of cardiac death, non-fatal myocardial infarction (Ml) 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.