Associations of Free and Reverse Triiodothyronine with Long-Term All-Cause Mortality After Acute Ischemic Stroke and Acute Myocardial Infarction

<b>Background:</b> Arterial thrombosis (AT), the main clinical manifestations of which are ischemic heart disease (IHD) and ischemic stroke (IS), is associated with lowered free triiodothyronine (fT3) in acute ischemic stroke (aIS) and acute myocardial infarction (aMI) but increased reverse T3 (rT3) in aMI, which are associated with worse outcomes at one year. Whether such associations remain independent over a longer follow-up period and the value of rT3 in aIS outcomes are largely unknown. This study was dedicated to examining the impact of fT3 and rT3 on aIS and aMI all-cause mortality over a longer 5-year period. <b>Methods:</b> Individuals from Lithuania who experienced aIS and aIM were included in this study. Serum fT3, rT3, free thyroxin and thyroid-stimulating hormone values were examined on admission to the intensive care department. Follow-up for all-cause mortality was divided into two time periods: 1 and 5 years. <b>Results:</b> The final study (aIS cohort age, 67.5 ± 9.6 years, 41.5% women and aMI cohort age, 61.8 ± 11.4 years, 28% women) consisted of 241 aIS and 289 aMI individuals, respectively. Lower fT3 was independently associated (OR = 0.41; 95% CI: 0.17-0.99, <i>p</i> = 0.049) with aIS, and higher rT3 (OR = 1.69; 95% CI: 1.06-2.67, <i>p</i> = 0.027) with aMI with increased all-cause mortality at 1 year. No associations were found between studied hormones and all-cause mortality at 5 years in both conditions. <b>Conclusions:</b> Lower fT3 in aIS and higher rT3 in aMI are associated with higher all-cause mortality at 1 year. No such associations were found at 5 years.