Longitudinal estimation of signal-averaged electrocardiograms in patients with Kawasaki disease.

Background: Myocarditis associated with Kawasaki (KD) disease is prominent, but rarely detected by conventional methods. The hypothesis of this study is to see if signal-averaged electrocardiogram can detect myocarditis with KD.

Methods: We obtained signal-averaged electrocardiograms from 71 patients with KD (mean age 2.8 +/- 2.9 years) in the acute (1st-4th week), subacute (5-7th week), and chronic (8th week or later) phases (mean study period 3.5 +/- 1.7 years). Sixteen patients who had pericardial effusion, bundle branch block or myocardial ischemia were excluded from this study. The results were compared with those of Holter and 12-lead electrocardiograms, echocardiography and serum myocardial enzymes. They were also contrasted with the course of each patient.

Results: The incidence of abnormal findings on signal-averaged electrocardiogram was 18.2% in the acute phase versus 10.9% in the subacute and chronic phases. It differed significantly higher than the other conventional tests (P < 0.05). Four patients had abnormalities of signal-averaged electrocardiograms through all three phases. Among these four, two had reduced left ventricular contractility. However, these changes were transient and resolved in the subacute phase. All patients had good courses and no residue.

Conclusion: This study shows the possibility that signal-averaged electrocardiogram is more useful to detect myocarditis associated with KD than the other conventional tests. However, we could not define the prognostic value of abnormal signal-averaged electrocardiograms during this study period.