The investigators will include a total of 500 children aged 4 weeks to 10 years who is consecutively referred to the Dept. of Paediatrics, Akershus University Hospital, for assessment of heart murmurs. All participants will be subjected to clinical examination, symptom assessment, pulse oximetry, blood sampling (for troponin T, proBNP and other biomarkers), ECG recording, and echocardiography. A randomized subgroup of children will also undergo echocardiography performed by a general practitioner who has not received formal training in pediatric cardiology. The value of possible predictors will be assessed through the construction of Receiver Operating Characteristics (ROC) curves, and calculation of negative predictive value.