OBJECTIVE: To investigate the long-term outcome of initially dilated/aneurysmatic coronary arteries in Kawasaki disease (KD) and to define risk factors for significant myocardial ischemia during follow-up, we retrospectively followed all pediatric patients with proven acute coronary changes due to KD in our institution. METHODS AND RESULTS: Since 1981, 38 children have been identified with coronary changes due to KD. The median age was 1.2 years (0.1-12.8). In 37 patients therapy with intravenous immunoglobulin was initiated within 9 days (1-30) after the beginning of KD. All received aspirin and three additionally received steroids. Median follow-up was 8.5 years (0.5-24.8). We defined two groups: A aneurysm/ectasia of the coronary artery < or =5.0 mm (n = 23) and B aneurysm size >5.0 mm (n = 15). During follow-up, all coronary aneurysms of group A regressed to normal size, whereas in 14 patients of group B (93%) the aneurysms persisted or even increased in size. Four patients of group B developed severe coronary stenosis at the proximal and/or distal end of the aneurysm and needed an intervention (endovascular balloon dilation and stent implantation (n = 2) or bypass surgery (n = 2)) after a median time interval of 9.8 years (1.0-15.6) after KD. They all had ECG changes preceding the intervention about 1 year in advance. Maximum aneurysm size >5 mm was a statistical significant predictive risk factor for myocardial ischemia. CONCLUSIONS: After KD, patients with a coronary aneurysm size >5.0 mm need close follow-up assessments because of an elevated risk for the development of coronary stenotic lesions. In case of new and even unspecific ECG changes, coronary imaging modalities (angiography, MRI) have to be considered. Therapy options vary from percutaneous catheter interventions to bypass surgery and have to be selected individually for each patient.