Evaulation of atrial conduction abnormalities and left atrial mechanical functions in patients with subclinical thyroid disorders

Abstract

INTRODUCTION: Changes of thyroid hormones levels may lead to effects, not only in ventricular function, but also atrial function. The aim
of this study was to investigate left atrial (LA) mechanical functions, atrial electromechanical coupling and P wave dispersion in patients
with subclinical thyroid disorders.

MATERIAL AND METHODS: Eighty patients with subclinical thyroid disorders and forty controls were included. A diagnosis of subclinical
thyroid disorders were reached with increased or decreased serum TSH and normal free T4 (fT4) levels. LA volumes were measured
using the biplane area length method and LA active and passive emptying volumes and fraction were calculated. Intra- and interatrial
electromechanical delay were measured by tissue Doppler imaging (TDI).

RESULTS: All groups had similar demographic findings. LA mechanical functions significantly impaired in subclinical thyroid disorders than control
group. Intra- and Interatrial delay, were measured significantly higher in patients with subclinical thyroid disorders than control group. PA lateral
and interatrial delay were positively correlated with TSH (r = 0.507, p = 0.006 and r = 0.455, p = 0.015, respectively) in subclinical hypothyroid patients.
There was negative correlation between TSH and interatrial delay (r = –0.492, p = 0.006) in subclinical hyperthyroid patients. Linear multivariate
regression analysis demonstrated that, TSH was the only an independent factor of interatrial delay in patients with subclinica tlhyroid disorders.

CONCLUSIONS: This study showed that impaired LA mechanical and electromechanical function in subclinical thyroid disorders. TSH was
an independent determinant of interatrial delay. Prolonged atrial electromechanical coupling time and impaired mechanical atrial functions
may be related to the increased incidence of arrhythmias.