A file photo shows Chen Yandong (left) talking with a patient. [Photo/Provided to chinadaily.com.cn]

Chen Yandong was a cardiologist with the First Affiliated Hospital of Harbin Medical University. His wife found something wrong with him half an hour after he went to bed.

"I found his skin had taken on cyanoderma, indicating a lack of oxygen," she told local media. "Although I gave him cardiopulmonary resuscitation immediately, I failed to save his life."

Zhao Jiyi, one of Chen's colleagues, said that based on his symptoms, he probably died of sudden cardiac death with overwork and heavy mental stress being major contributors.

According to Zhao, since he began to work in the hospital in 2005, Chen had spent more than 14 hours on the job every day.

"He arrived at the hospital at 7 in the morning because he had to finish doing the rounds in about 30 wards before 8," Zhao said. "Then he would do a dozen heart stent surgeries, each of which took about one hour."