Correlation between the Level of Serum Free Triiodothyronine and the Degree of Myocardial Injury in Patients with Acute ST Segment Elevation Myocardial Infarction

Abstract

Background: Previous studies have suggested that hypothyroidism correlated with coronary artery diseases (CAD) mortality in long-term cohort studies, but whether the thyroid function status is associated with myocardial injury in acute ST-elevation myocardial infarction (STEMI) has not been investigated sufficiently. Aim: We aimed to investigate whether the lower free triiodothyronine level in acute STEMI is associated with more severe myocardial injury. Methods: This was a prospective observation cohort study that was conducted from August 2016 to April 2017 and included 50 patients presented to the coronary care Unit in Al Mataryia teaching hospital with acute STEMI and treated with thrombolysis. All patients were subjected to complete clinical assessment, serial ECGs, Echo, full labs, thyroid hormones, cardiac biomarkers, C-reactive protein (CRP). Results: There were 8 patients (16%) who had hypothyroidism including low-T3-syndrome (4 patients, 8%), subclinical hypothyroidism (3 patients, 6%) and clinical hypothyroidism (1 patient, 2%). After adjusting for conventional risk factors (age, gender, smoking, diabetes mellitus, dyslipidemia, hypertension), free triiodothyronine (FT3) was significantly and negatively correlated with CKMB (r=-0.294, P=0.038), cTnI (r=-0.368, P=0.009), and positively correlated with EF (r=0.385, P=0.006), indicating that the lower thyroid hormone level correlates with the more severe cardiac injury in STEMI patients. FT3 also had a negative correlation with CRP (r=-0.404, P=0.004), which might indicate that hypothyroidism may activate the inflammation response. Conclusion: The lower FT3 level correlates with higher level of cardiac biomarkers and lower left ventricular ejection fraction (LVEF), Low T3 syndrome may be a predictor for myocardial injury in STEMI. These results may warrant further study to investigate whether reversing the hypothyroidism could benefit the STEMI patients.