QT interval prolongation in asymptomatic anti-SSA/Ro-positive infants without congenital heart block

Objective. To analyze the electrocardiograms (EKGs) of infants born to mothers with anti-SSA/Ro antibodies in order to evaluate the QT interval (the time from the beginning of the QRS complex to the end of the T wave). Methods. Sera from mothers and children were analyzed for anti-Ro and anti- SSB/La antibodies by enzyme-linked immunosorbent assay (ELISA) and by Western blot analysis. Fine specificity of anti-Ro antibodies was evaluated by solid- phase ELISA against recombinant 52- and 60-kd proteins and by Western blot. A retrospective chart review was conducted for EKG analysis. Twenty-eight EKG tracings (21 from anti-Ro-positive and 7 from anti-Ro-negative infants born to mothers with autoimmune diseases) were analyzed by a single investigator who was blinded to the infant's antibody status. The QT interval was measured and corrected for heart rate according to Bazett's formula. Results. The mean QT interval was significantly longer in anti-Ro-positive than in anti-Ro- negative infants, also after correction for heart rate (QTc) (P = 0.001). Nine of 21 anti-Ro-positive infants and 0 of 7 anti-Ro-negative infants had QTc values above the upper normal limit (440 msec). A 24-hour EKG recording was performed on 5 patients and confirmed the QT prolongation. These infants were subsequently treated with a beta-blocker in order to prevent arrhythmias. Conclusion. Infants born to mothers who carry anti-Ro autoantibodies may show QT interval prolongation and should be monitored with EKG during the first months of life.