Q: What is the difference between Orthotopic and the Heterotopic heart transplant?

Answer:

In Orthotopic heart transplant, the failing heart is removed (The pulmonary veins are not transected; rather a circular portion of the left atrium containing the pulmonary veins is left in place). The donor heart is trimmed to fit onto the patient's remaining left atrium and the great vessels are sutured in place.

In Heterotopic heart transplant, the patient's own heart is not removed before implanting the donor heart. The new heart is positioned so that the chambers and blood vessels of both hearts can be connected to form what is effectively a 'double heart'. The procedure can give the patients original heart a chance to recover, and if the donor's heart happens to fail (e.g. through rejection), it may be removed, allowing the patient's original heart to start working again.