We present a 3.5-year-old patient with tetralogy of Fallot, pulmonary atresia, and major aortopulmonary collaterals, after repeat implantation of a central shunt, in whom we successfully re-purposed previous imaging scans with a novel image fusion software to guide diagnostic heart catheterisation. The pre-registered CT scan was segmented before the procedure and subsequently manually fused with two-dimensional fluoroscopy images. The overlaid roadmap enhanced selective cannulation of all major vessels originating from the aorta, making aortography unnecessary.