Correlation of QT interval with disease activity in newly detected SLE patients at baseline and during flare

To study correlation between QT interval parameters (QTc interval & QT dispersion) and disease activity (SLEDAI) in patients with systemic lupus erythematosus (SLE). The study was done on 100 newly diagnosed patients with SLE and 100 age matched controls from January 2012 to December 2013. A standard 12 lead Electrocardiogram was obtained. QT interval was calculated from beginning of ‘q’ wave to end of T wave in lead II or lateral leads (V5, V6). QT dispersion was measured as the difference between maximum and minimum QT intervals. SLE disease activity was measured SLEDAI. Eighty four patients had high disease activity. QTc was >440 msec in 51 patients and 6 controls. QTd was prolonged in 6 patients and 6 controls. The mean QTc interval among patients (463.30 ± 27.43 msec) was higher than in controls (397.24 ± 31.85 msec; p < 0.001). However the mean QTd among patients (44.40 + 20.61 msec) was similar to that in controls (39.2 + 17.7 msec). Difference of QTc values during severe flare from baseline QTc values was statistically significant (r = 0.863; Pearson's correlation coefficient). Patients with high disease activity have higher prevalence of QTc prolongation, QTc interval may be used as a surrogate marker for assessing disease activity in SLE.