Effects of Thyroxine Therapy on Right Ventricular Systolic and Diastolic Function in Patients with Subclinical Hypothyroidism: A Study by Pulsed Wave Tissue Doppler Imaging

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Abstract
Introduction: The effects of l-thyroxine (l-T4) replacement for subclinical hypothyroidism (SH) on right ventricle (RV) functions has not been previously studied by means of pulsed wave tissue Doppler imaging (PWTDI). We investigated the effects of l-T4 therapy on RV function in patients with SH using PWTDI. Patients and Methods: Fifty-three patients with newly diagnosed SH and 25 controls were evaluated by standard echocardiography and PWTDI. After euthyroidism was restored by l-T4, measurements were repeated. Myocardial systolic wave (Sm) velocity, isovolumic acceleration (IVA), myocardial precontraction time (PCTm), and PCTm to contraction time (CTm) ratio were calculated as systolic indices. Early (Em) velocity, late (Am) velocity, Em to Am ratio, and myocardial relaxation time (RTm) were determined as diastolic measurements. Results: Sm was similar in patients and controls, whereas IVA was significantly lower in patients with SH (P < 0.001). SH patients had significantly decreased Em velocity, whereas Am velocity and Em to Am ratio did not differ. PCTm and RTm were significantly longer, and PCTm to CTm ratio was significantly higher in patients (P = 0.002, P = 0.002, P < 0.001, respectively). Sm velocities were similar before and after l-T4 replacement, whereas IVA significantly increased after therapy (P < 0.001). Em tended to increase (P = 0.05), whereas Am and Em to Am ratio were not changed. PCTm, PCTm to CTm ratio, and RTm decreased significantly (P < 0.001 for all). Conclusions: SH is associated with RV systolic and diastolic dysfunction, and l-T4 treatment improves these abnormalities. PWTDI, especially IVA, may be a suitable tool for the early detection of RV systolic dysfunction.

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