Mother hears her dead son's heart beating inside a four-year-old child

This video shows the emotional moment the mother of a baby who died at seven months old has heard her son's heartbeat inside a four-year-old girl.

Heather Clark listened to the rhythm of her son Lukas's heart at Phoenix Children's Hospital, in the USA after four-year-old Jordan Drake received the heart after a transplant.

Jordan was suffering from a congenital defect.

When Lukas died in 2013, allegedly from injuries he sustained at the hands of his babysitter's boyfriend, Clark wanted her son's organs donated.