This used to be a favourite lecture of mine, to describe cases where heart failure or cyanosis was present but with a morphologically normal heart. The usual culprits were hyperdynamic heart failure in systemic (usually cerebral) arteriovenous malformations, and cyanosis from pulmonary AVMs. With only the angio as an imaging tool, we would have a regular stream of infants in unexplained heart failure for us to sort out in the cardiac unit. Today of course other imaging is available to the neonatologist.
There was one which was quite an event, a neonate who was in deep trouble from birth, in severe cardiorespiratory distress. Intubated to little effect, this chest film was taken just before a rapid transfer to our cardiac unit.
On arrival, the child was moribund, and was taken to theatre for urgent institution of cardiac bypass to keep it alive. As the surgeon said, what after that? So we all gathered around the viewer and looked at this chest film for a while. Then one bright spark noticed the anterior spinal defect partly obscured by the endotracheal tube, and diagnosed a neural cyst of some sort. Which it was, filling nearly all the chest. We pulled in a neurosurgeon and opened the chest and the cyst came out remarkably well.