"Gao Gao has a heart disease that will continue to progress,'' Sadler said. "Unfortunately, we can't cure this disease, but we definitely can provide him with excellent medical care and make his quality of life good.
"He is responding very well to his treatment, and we will continue to monitor the progression of his disease, so we can keep him as healthy and content as possible,'' the vet said.
Sadler and UC Davis veterinary cardiologist Joao Orvalho performed an ultrasound examination on Gao Gao on Tuesday.
Pulmonary stenosis is most commonly the result of a birth defect, according to the zoo. Symptoms can include a heart murmur, a low tolerance for exercise and fatigue.
Veterinarians think Gao Gao also has high blood pressure.
Giant pandas are on loan from China for research purposes. Gao Gao lives with the female panda Bai Yun and their 3-year-old son Xiao Liwu.
Around 1,600 giant pandas are believed to exist in the wild, but those numbers may be growing due to dedicated conservation efforts.