Effect of Short-Term L-Thyroxine Therapy on Left Ventricular Mechanics in Idiopathic Dilated Cardiomyopathy

Abstract

Previous experimental studies have provided evidence of notable changes in thyroid hormone signaling that corresponds to alterations in myocardial function in animal models of heart failure (HF). The present study further explores whether oral thyroid hormone treatment can change left ventricular (LV) mechanics and functional status in patients with idiopathic dilated cardiomyopathy (IDCM) or not. Sixty IDCM patients who were receiving conventional HF treatment were randomized to oral L-thyroxine (n=40) or placebo (n=20) for 3months. Fifty-two (86.7%) of all IDCM patients were symptomatic, their mean age was 41±12years, and their ejection fraction was 32%±7%. At baseline, the two groups were comparable in clinical and echocardiographic variables. Vector velocity imaging was utilized to assess LV mechanics. Myocardial longitudinal peak systolic strain, systolic strain rate, early and late diastolic strain rate, circumferential strain, LV dyssynchrony, plasma tri-iodothyronine, thyroxine, and thyroid stimulating hormonelevels were measured at baseline and 3months after treatment. All patients receiving L-thyroxine significantly improved in functional status (New York Heart Association class; P<.001) and echocardiographic parameters including end-diastolic diameter (P<.001), end-systolic diameter (P<.001), mitral regurgitation severity reduction (P<.001), and increased ejection fraction (P<.001). Left ventricular mechanics showed marked improvement at segmental and global levels of both longitudinal and circumferential myocardial strain (P<.005) when compared with placebo group. Short-term L-thyroxine therapy is well tolerated in IDCM patients. It improves cardiac mechanics and functional status, which might support the potential role of synthetic thyroid hormones in HF treatment.