Subclinical Hypothyroidism is a Useful Predictor of Adverse Events in Heart Failure Patients with Reduced Left Ventricular Ejection Fraction

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Thyroid dysfunction has an adverse effect on cardiac function and relates to poor prognosis of patients with heart failure (HF), but data of hypothyroidism as a predictor of adverse events are scarce. In this study, we evaluated the predictive value of subclinical hypothyroidism for poor outcome in HF. Continuous 71 ambulatory patients with HF with reduced LVEF who had never received thyroid hormone replacement therapy were enrolled. We assessed their baseline thyroid-stimulating hormone (TSH) and classified them into euthyroid (TSH: 0.35 to 5.50 uU/ml), hypothyroid (>5.50 uU/ml), or hyperthyroid (<0.35 uU/ml). We defined cardiovascular death or hospitalization for HF as study endpoints and compared outcomes among 3 thyroid states. Furthermore, we evaluated the prognostic value of TSH for poor outcome, using multivariate Cox proportional-hazards model. Sixty-one patients (85.9%) had euthyroidism, 8 patients (11.3%) hypothyroidism, and 2 patients (2.8%) hyperthyroidism. Kaplan-Meier event-free survival analysis revealed that the patients with hypothyroidism showed worse event-free survival compared to those with euthyroidism (p=0.013). Multivariate analysis demonstrated that TSH was a significantly independent predictor of adverse events after adjustments for age, gender, LVEF, and BNP. (HR: 1.216; 95% CI: 1.029 to 1.438; p=0.022). More than 10% of HF patients with reduced LVEF had subclinical hypothyroidism which demonstrated poor prognosis. High TSH level was a useful predictor of adverse events.