Impact of low T3 syndrome on adverse cardiovascular events in adult patients with acute viral myocarditis

Abstract

Objective: To determine the impact of low T3 syndrome on adverse cardiovascular events in adult patients with acute viral myocarditis. Methods: The study population consisted of 134 consecutive patients admitted between January 2002 and March 2018 with diagnoses of acute viral myocarditis (onset of symptoms<1 month,patients were divided into low serum free triiodothyronine (FT3, n=20) group and normal FT3 (n=114) group. General information, clinical presentation,electrocardiography at admission,laboratory tests,echocardiography features were analyzed. Low T3 syndrome was defined as a state with decreased FT3 and total triiodothyronine (TT3), normal or decreased free thyroxine (FT4) and total thyroxine (TT4) as well as normal thyroid stimulating hormone (TSH). Composite adverse cardiovascular events included death, persistent ventricular tachycardia (VT) or ventricular fibrillation (VF) and cardiac arrest. Risk factors related with composite adverse cardiovascular events in adult patients with acute viral myocarditis were analyzed by logistic regression analysis. Results: Systolic blood pressure was significantly lower (P<0.01),while heart rate (P=0.004) and the prevalence of VT/VF were significantly higher (P=0.017) in low T3 group than in the normal T3 group. Level of white blood cell,C response protein,fasting glucose (all P<0.01) as well as creatinine (P=0.035) were significantly higher, while level of FT3 and left ventricular ejection fraction (LVEF) were significantly lower (both P<0.01) in low T3 group than in normal T3 group. Multivariate logistic regression analysis revealed that LVEF at admission less than 40% (OR=6.615,95%CI 1.186-36.907, P=0.031) and FT3 level less than 1.79 ng/L (OR=9.131, 95%CI 1.577-52.857, P=0.014) were independent risk factors of increased composite adverse cardiovascular events in patients with acute viral myocarditis. Conclusion: Low FT3 increases the risk of adverse cardiovascular events in adult patients with acute viral myocarditis.