Echocardiographic Z-score models play a crucial role in defining cardiac pathology in paediatric patients. There are multiple models that practitioners utilize in the United States without guiding principles to standardize their use. Discrepant interpretations can occur depending on the model chosen, even if standardized Z-score cutoffs are applied. In this study, a survey was developed to assess pediatric cardiologists’ use of Z-score systems when evaluating and treating patients with isolated bicuspid aortic valve. The majority of respondents reported using Z-score cutoffs to evaluate the degree of aortic root and ascending aorta dilation. For the aortic root, mild, moderate, and severe dilation averaged at 2.13 (SD = 0.32), 3.59 (SD = 0.49), and 5.11 (SD = 0.84), respectively. Similar cutoffs were reported for determining ascending aorta dilation. A large proportion of respondents primarily used the Boston system (36%, 18/50) or Boston and Pediatric Heart Network systems together (36%, 18/50). There were also differences in management decisions, such as implementing competitive sports restrictions, based on Z-scores and the 2015 Task Force 7 Bethesda exercise guidelines. These survey results demonstrate variability that exists among paediatric cardiologists in their use of Z-scores for describing aortic root and ascending aorta dilation in patients with isolated bicuspid aortic valve and suggests the need for implementation of national guidelines for Z-score usage.