Former Vice President Cheney is “doing great” on Friday and personally returning calls from strangers who wished him well following his heart transplant, according to an aide.

Cheney has been calling “perfect strangers” to thank them for sending him get-well cards, Cheney spokesperson Kara Ahern told Fox News. “Most of them are shocked when he tells them who is calling.”

Cheney, who has a history of heart trouble, had a heart transplant last Saturday. He had been on the donor wait list since June 2010 and waited longer than average for the organ, according to ABC News.