Association Between Low T3 Syndrome and Poor Prognosis in Adult Patients With Acute Myocarditis

Abstract

Background: This study aims to investigate the role of free triiodothyronine (fT3) in predicting poor prognosis of adult patients with acute myocarditis.

Methods: A total of 173 consecutive adult patients with acute myocarditis completed thyroid function evaluations. They were divided into two groups according to fT3 levels: low fT3 group (n = 54, fT3 < 3.54 pmol/liter) and normal fT3 group (n = 119, fT3 ≥ 3.54 pmol/liter). The primary endpoint was major adverse cardiac events (MACE).

Results: During the 3.5 ± 2.8 years follow-up, the rate of MACE was 29.6% versus 3.5% in low fT3 group versus normal fT3 group, respectively (P < 0.0001). Long-term at 8 years MACE-free survival were lower in low fT3 group versus normal fT3 group (52.9% versus 92.3%, log-rank P < 0.0001), respectively. Univariate Cox analysis showed that left ventricular ejection fraction (LVEF) < 50% [hazard ratio (HR) 10.231, 95% confidence interval (CI): 3.418-30.624, P < 0.0001) and low fT3 level (HR 0.360, 95% CI: 0.223-0.582, P < 0.0001) were strongest two predictors of MACE. After adjustment for traditional risk predictors, the prognostic value of fT3 status was still significant (HR 0.540, 95% CI: 0.316-0.922, P = 0.024). Compared with normal fT3 group, those in low fT3 group were at a much higher risk of MACE (HR 5.074, 95% CI: 1.518-16.964, P = 0.008).

Conclusions: Low T3 syndrome was a strong predictor of poor prognosis in adult patients with acute myocarditis. These findings suggest that fT3 level could serve as a biomarker for risk stratification in acute myocarditis patients.

Keywords: acute myocarditis; adult; low T3 syndrome; predictor; prognosis.

Figure 1

The flow chart of the enrollment of 173 adult patients with acute myocarditis from the overall population with acute myocarditis. 15 patients who had been treated before admission with drugs that might affect thyroid function were excluded.

Figure 2

Long-term (A) and 30-day (B) MACE-free survival in low fT3 group versus normal fT3 group in patients with acute myocarditis. Patients with low fT3 syndrome had more MACE in 30 days as well as in the long-term. MACE included deaths, heart transplantations, re-hospitalization for heart failure and sustained ventricular arrhythmias (>30s).

Figure 3

Scatter figure showed a linear correlation between fT3 concentrations and time of survival (days, logarithmic scale) in all patients who had MACE (n = 20). MACE, major adverse cardiac events; fT3, free triiodothyronine.

Figure 4

The MACE-free survival probability curve of patients with acute myocarditis and combination of low fT3 status and LVEF are displayed. Patients with LVEF ≥50% and fT3 ≥3.54pmol/liter have a significantly better prognosis compared to those with LVEF ≥50% and fT3 <3.54pmol/liter. Patients with LVEF <50% have worse outcome compared to those with LVEF ≥50%. Patients with LVEF <50% and fT3<3.54pmol/liter have the worst outcome than those with normal fT3 status. MACE, major adverse cardiac events; fT3, free triiodothyronine; LVEF, left ventricular ventricle ejection fraction.

Figure 5

Receiver operating characteristic (ROC) curve of the ability of LVEF and fT3 to predict MACE in patients with acute myocarditis. The area under curve (AUC) for LVEF was 0.840. The sensitivity and specificity were 75.00% and 87.07%, respectively. The AUC for fT3 was 0.779, with 80.00% sensitivity and 74.15% specificity. MACE, major adverse cardiac events; fT3, free triiodothyronine; LVEF, left ventricular ventricle ejection fraction.