Survey participation/response rate by country and region. Survey participation/response rate by country and region. Hospitals were eligible if contact data of one clinician dedicated to the field of paediatric cardiology were available. We were able to find contact data of physicians from 204 different hospitals in 39 European countries. Four were excluded from analysis: one physician contacted expressed his wish not to participate, one did not feel able to participate because of limited experience, one was retired and one returned the completed questionnaire after the pre-established deadline. If more than one physician in a hospital answered, only the first questionnaire received was taken into consideration for analysis. Response rate was calculated as the number of different hospitals from which at least one physician submitted a completed or partially completed questionnaire divided by the number of different hospitals from which a physician was sent the invitation with questionnaire link. Criteria of the United Nations statistical division for Europe41 were followed for the classification of countries by European region. Four of the countries referred to are not considered as being European in this classification. Armenia and Azerbaijan were assigned here to Eastern Europe, Cyprus and Turkey to Southern Europe.  Cristina Castro Díez et al. bmjpo 2019;3:e000365 © Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.