To assess myocardial electric potentials late after Kawasaki disease (KD) we measured signal-averaged electrocardiography (SAECG) and QT dispersion parameters. Thirteen patients with persistent coronary aneurysm (group I), 12 with late resolution of the aneurysm (>3 months) (group II), and 13 with early resolution (group III) were studied 7.9 +/- 3.9, 6.7 +/- 3.9, and 7.2 +/- 3.6 years after the initial diagnosis (p = NS). In group I, myocardial infarction occurred in one patient during the acute illness, and coronary thrombosis in another; all except two patients had giant aneurysm (n = 8) and/or stenosis (n = 7). At 40-Hz high-pass filter SAECG, terminal 40-msec root mean square amplitude (RMS40) was significantly lower in group I versus II and III (64.1 +/- 40.8 microV, 79.9 +/- 47.2 microV, and 115 +/- 65.4 microV, respectively; p <0.05). Global QT dispersion was significantly greater in group I versus III (52 +/- 11 msec and 37 +/- 11 msec, respectively; p <0.05), but not in comparison to group II (45 +/- 13 msec). The same trend was present for rate-corrected QT dispersion, without reaching statistical significance (84.0 +/- 34, 71.5 +/- 31, and 61.8 +/- 21 respectively). Both depolarization and repolarization parameters are altered in patients with persistent coronary artery aneurysms long-term after KD. This may represent risk factors for developing ventricular arrhythmia in a growing population.