Low-T3 syndrome and signal-averaged ECG in hemodialyzed patients

Abstract

The study was designed to evaluate the potential link between low-T 3 syndrome and signal-averaged ECG parameters (SAECG) in a group of hemodialyzed patients (HD-pts). 52 selected HD-pts (without relevant thyroid and cardiac diseases) were included. SAECGs were performed postdialysis together with evaluating free triiodothyronine (fT3), free thyroxine (fT 4), reverse triiodothyronine (rT3), thyroid stimulating hormone levels and echocardiography. For each SAECG, QRS duration (QRSd), root-mean-square voltage of the terminal 40 ms of the QRS (RMS40), and low-amplitude signal duration (LAS40) were measured. Abnormal SAECGs were found in 30.8% of HD-pt. HD-pts with decreased TT3 and increased rT 3 values (low-T3 positive) revealed higher QRSd and LAS40 values in comparison with low-T3 negative HD-pts (p=0.019, p<0.001 respectively). LoW-T3 positive HD-pts had lower RMS40 values than low-T3 negative patients (p<0.001). The Pearson test showed significant correlations between QRSd and fT3 (r=-0.592, p<0.001); QRSd and rT3 (r=0.562, p<0.001); RMS40 and fT3 (r=0.432, p=0.009); RMS40 and rT3 (r=-0.325, p=0.025). On multivariate analysis, both fT3and rT3 levels were found to be independent predictors of QRSd and RMS40 values. Our study showed that decreased fT3 and increased rT3 concentrations due to low-T3 syndrome influence SAECG parameters in HD-pt. © 2005 Institute of Physiology, Academy of Sciences of the Czech Republic.