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

Departments of Cardiology (S.T., C.T., M.K., I.D., B.C., C.E.) and Endocrinology and Metabolic Diseases (M.O.C., A.G., S.G.), Ankara University School of Medicine, 06100 Ankara, Turkey

Address all correspondence and requests for reprints to: Dr. Sibel Turhan, Department of Cardiology, Ibn-i Sina Hospital, 06100 Samanpazari, Ankara, Turkey. E-mail: sblturhan{at}yahoo.com.

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 (S_m) velocity, isovolumic acceleration (IVA), myocardial precontraction time (PCT_m), and PCT_m to contraction time (CT_m) ratio were calculated as systolic indices. Early (E_m) velocity, late (A_m) velocity, E_m to A_m ratio, and myocardial relaxation time (RT_m) were determined as diastolic measurements.

Results: S_m was similar in patients and controls, whereas IVA was significantly lower in patients with SH (P < 0.001). SH patients had significantly decreased E_m velocity, whereas A_m velocity and E_m to A_m ratio did not differ. PCT_m and RT_m were significantly longer, and PCT_m to CT_m ratio was significantly higher in patients (P = 0.002, P = 0.002, P < 0.001, respectively). S_m velocities were similar before and after L-T₄ replacement, whereas IVA significantly increased after therapy (P < 0.001). E_m tended to increase (P = 0.05), whereas A_m and E_m to A_m ratio were not changed. PCT_m, PCT_m to CT_m ratio, and RT_m 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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