Is a right-handed person who was born with a heart condition called Dextrocardia to wear the Tefillin on his left arm?[1]

Yes. The condition of dextrocardia, in which the heart is found by the right side of the chest, does not change the law regarding onto which hand the Tefillin is to be worn, and hence a righty is to wear it on his left arm despite having such a condition.

[1] Eretz Tzevi 1:115; Piskeiy Teshuvos 27:1