The first paediatric heart transplant was performed by Adrian Kantrowitz and his team on 6th December 1967 at the Maimonides Medical Center in Brooklyn. It was three days after the world’s very first heart transplant by Dr. Christiaan Barnard in South Africa.
FYI, the world’s first successful heart surgery was on Wilhelm Justus by German surgeon Ludwig Rehn on 7th September 1896.
