Application of Signal-Averaged Electrocardiogram to Myocardial Damage in the Late Stage of Kawasaki Disease

Background Myocardial damage occurs in the late stage of Kawasaki disease (KD) regardless of whether coronary artery lesions (CALs) are present. Methods and Results A signal-averaged electrocardiogram (ECG) was performed in 23 patients who were in the late stage of KD (CAL was found in 12 and no CAL (non-CAL) was found in 11) and 10 healthy controls. Filtered QRS duration and the root-mean-square voltage in the last 40ms of the QRS complex were measured using time-domain analysis. Additionally, the area ratio (AR), (area of 20-50Hz)/(area of 0-20Hz)×100, was calculated by frequency domain analysis. These findings were compared with the clinical data and histopathological findings. In time-domain analysis, there were no significant differences among the 3 groups. In frequency domain analysis, the AR in CAL was significantly higher than that in the other 2 groups. Furthermore, all 4 patients who underwent an endomyocardial biopsy showed a high AR and abnormal histopathological features. Conclusions The findings of the present study suggest that patients in the late stage of KD have abnormal findings on signal-averaged ECG even without stenotic lesions, arrhythmia or ischemia, a condition that might reflect histopathological changes in the myocardium in the late stage of KD.