[Verse 1]
When hearts are born with tangled pipes
One vessel where there should be two
The pulmonary branches must decide
Which pathway they will tunnel through
Collett saw the patterns first
In forty-nine he mapped the ways
Four types of arterial dispersal
Each with its anatomic phrase
[Chorus]
Type One's got a trunk that splits in two
Sixty percent take this route
Type Two springs from separate holes
Twenty to thirty, that's the scoop
Type Three spreads wide across the walls
Ten percent choose the distant climb
Type Four's got no arteries at all
Just collaterals feeding time
[Verse 2]
Van Praagh came sixteen years later
With letters marking different scenes
A-one through A-four classifications
Refining what the structure means
A-two matches our Type Two patient
No main segment to be found
Left and right from separate doorways
Spiral dancing, tightly wound
[Chorus]
Type One's got a trunk that splits in two
Sixty percent take this route
Type Two springs from separate holes
Twenty to thirty, that's the scoop
Type Three spreads wide across the walls
Ten percent choose the distant climb
Type Four's got no arteries at all
Just collaterals feeding time
[Bridge]
Left PA climbs anterior and high
Right PA drops posterior and low
Separate ostia on the posterior face
Where truncal blood decides to flow
No main segment here to guide the way
Just twin portals in the wall
Each branch carving its own journey
From the common truncal hall
[Verse 3]
Type Four became its own disease
Pulmonary atresia with VSD
When arteries refuse to form at all
And collaterals must guarantee
The blood supply to hungry lungs
Through tortuous pathways they create
A different beast entirely
Not truncus, but a separate fate
[Outro]
Remember when you see truncus
Check where those vessels arise
Separate holes or single trunk
The pattern never lies