The aim of the study was to noninvasively assess endothelial cell (EC) function in the microcirculation using laser Doppler fluximetry (LDF) in acute and convalescent Kawasaki syndrome (KS) patients and healthy controls. KS is an acute, self-limited vasculitis of childhood that affects the EC of medium-sized arteries. No studies have addressed EC function in the peripheral microcirculation. LDF preacetylcholine and postacetylcholine (ACh) iontophoresis estimates microcirculation EC nitric oxide production leading to smooth muscle relaxation and vasodilatation, which are blunted in EC dysfunction. We studied a total of 97 subjects: 36 acute and 27 convalescent KS patients and 34 normal children. Change in blood flow was measured by LDF for 10 min postACh iontophoresis. Acute KS patients had significantly lower average flux when compared to convalescent KS patients and controls in the first 5 min postiontophoresis. However, there was no difference in flux or area under the curve (AUC) between convalescent KS patients and healthy controls. Despite a reduced response of the microvascular EC to ACh in acute KS patients, convalescent patients with and without coronary aneurysms had microvascular EC function similar to normal controls. This suggests that the EC injury in KS is confined to the endothelium of mediumsized arteries and that microvascular EC function is normal after acute KS. KeywordsCoronary artery aneurysm; Vasculitis; Pediatric heart disease Correspondence to: Jane C. Burns, jcburns@ucsd.edu. [12]. The result of these assumptions is an average flux in the area of interest that can be measured before and after iontophoresis of ACh. This technique has been used in the past to study adults with conditions known to affect the microcirculation such as diabetes. To study the ability of the endothelium to release nitric oxide, LDF is coupled with ACh iontophoresis to produce vascular smooth muscle relaxation in response to nitric oxide. The resultant vasodilation can be measured as a change in flux. Limited experience in older pediatric patients suggested that the technique might be adaptable for the study of infants and young children. We used LDF before and after ACh iontophoresis to study EC function in the microvasculature of healthy children and in children during the acute and convalescent stages of KS. Materials and Methods PatientsThree populations of subjects were studied: acute and convalescent KS patients and healthy pediatric controls. Acute KS patients were studied during their admission to the hospital for treatment with IVIG and high-dose ASA. Acute patients were studied when their rectal or oral temperature was less than 100.4°F so that elevated body temperature would not complicate the interpretation of the study. Patients older than 3 years of age who were able to cooperate with the study were evaluated without sedation. The remaining acute KS patients were studied by LDF after receiving chloral hydrate sedation for echocardiograms that were performed either during or shortly after IV...

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