Impaired cardiac adrenergic innervation assessed by MIBG imaging as a predictor of treatment response in childhood dilated cardiomyopathy

Objective - To evaluate the prognostic value of metaiodobenzylguanidine (MI BG) imaging in childhood cardiomyopathy. Design - Prospective cohort study. Setting - Tertiary referral centre. Patients - 40 children (21 boys, 19 girls; mean (SD) age, 7.0 (5.6) years) with heart failure resulting from idiopathic dilated cardiomyopathy (n 23) or various other disorders (n = 17). Methods - At the initial examination, cardiac I-123-MIBG uptake and release , circulating noradrenaline (norepinephrine) concentration, x ray cardiotho racic ratio, and echocardiographic variables were recorded. Cardiac MIBG up take was obtained by measuring the heart to mediastinum activity ratio on t he planar image obtained four hours after MIBG injection. MIBG washout rate was evaluated using relative decrease in cardiac activity measured at 20 m inutes and four hours. Patients were treated with angiotensin converting en zyme inhibitors, diuretics, and digitalis, and were followed up for 12 (10) months. Fifteen patients did not respond to medical treatment (12 heart tr ansplants; three deaths), and 25 did respond (improved or stable). Results - Cardiac MIBG uptake was positively correlated with x ray cardioth oracic index (r 0.55, p = 0.0008) and echocardiographic left ventricular fr actional shortening (r = 0.68, p < 0.0001). Among all the clinical and labo ratory variables tested, multivariate discriminant analysis showed that the only independent predictor of an unfavourable outcome was a low MIBG uptak e (p < 0.001). Survival curves had a mean threshold value of 1.54 for MIBG uptake. Conclusions-impaired cardiac adrenergic innervation is strongly related to adverse outcome in children with dilated cardiomyopathy, independently of t he aetiology. MIBG imaging may help to stratify risk in such patients.