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

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 subclinical thyroid 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.