Footnotes

• Contributors PML: conceptualised and designed the study, performed echocardiography studies, analysed data, wrote the manuscript. AS: designed the study, performed echocardiographic studies, reviewed the manuscript. JT: performed echocardiographic studies, reviewed the manuscript. MJ: performed echocardiographic studies, reviewed the manuscript. AJ: helped design the echocardiography rating scale, including conducting pilot testing of the scale, scored all echocardiographic studies, reviewed the manuscript. EK: conducted the randomisation, prepared oral study solutions for the infants, reviewed the manuscript. EC: performed echocardiographic studies, reviewed the manuscript. PB: helped design the echocardiography rating scale, reviewed the manuscript. PJM: helped design the echocardiography rating scale, including conducting pilot testing of the scale, scored all echocardiographic studies, wrote the manuscript. RB: conducted the statistical analyses, contributed to the initial draft of the manuscript. LH: conceptualised and designed the study, obtained external funding, performed some of the data analysis (reliability), wrote manuscript. All authors reviewed and approved the final manuscript as submitted

• Funding This study was funded by the Alva Foundation (to LH). PML is supported by Clinician-Scientist Awards from the CFRI and the Michael Smith Foundation for Health Research (MSFHR). LH is supported by a Canadian Institutes of Health Research Canada Research Chair.

• Competing interests None declared.

• Patient consent Obtained.

• Ethics approval Children's & Women's Health Centre of British Columbia (C&W) Research Ethics Board (#H10-02069).

• Provenance and peer review Not commissioned; externally peer reviewed.