I understand the concept of Great vessel transposition. My question is since both the fingers and toes are located in the systemic circulation, what is the reasoning behind the fact that the fingers become cyanotic faster than the toes?
cyanosis of the fingers > toes
means the lower extremities are getting oxygenated blood, while the upper extremities are getting blood w/lower oxygen.
This can happen if you have complete transposition of the great vessels with coarctation before the patent ductus arteriosis ("preductus") or complete interruption of the aortic arch, with pulmonary hypertension and a reverse shunt through the patent ductus. delivering oxygenated blood to the lower extremities.
Agreed, good question. Sorry, in hindsight my response probably seemed a little glib. When I was first asked something like this question, having a picture in my mind helped (I'm sort of a split auditory/visual learner) to figure it out. But the way the question was worded to me was "what could cause reverse differential cyanosis" (and as D99 correctly intimated, D-TGA in and of itself does not always present with such)
And by the way: if the original question had been presented (incorrectly) as why do all D transposition present with cyanosis of the fingers first, it could be that the questioner was referring to when D-TGA presents at an earlier closure of the ductus (i.e. early neonatal period) at a time when there is still a high PVR (essentially acting as if there was pulmonary hypertension)