Yan Hui, head of the China-Tajikistan Medical Diagnosis and Treatment Center in Dushanbe, said that many Tajik children with congenital heart defects remain on waiting lists due to limited medical resources in Tajikistan and financial constraints.

After a similar program in Northwest China's Xinjiang Uygur autonomous region last year, inquiries from Tajik families seeking treatment in China have increased.

"The parents and children don't speak Mandarin, but they kept asking me to teach them simple phrases like 'thank you, Chinese doctor'," Yan said. "Over time, the phrase became a catchphrase during their stay here."