A 44-year-old teacher is in urgent need of a heart transplant due to severe cardiac failure, with his spouse calling the procedure "the only hope of survival".

The Hospital Authority (HA) on Thursday said the male patient is in critical condition at the intensive care unit of Queen Elizabeth Hospital.

In a voice recording released to the media, the patient's wife said a heart transplant is the only hope for his survival.

"Our two children are still young and they need their father's company as they grow up," she said. "I hope there is a kind person who will help our family and give my husband a chance to live."

The patient, a teacher at a Tung Chung school, experienced chest pain after exercising on October 20 and sought help at Tseung Kwan O Hospital.

A scan a day later showed the patient suffered from acute aortic dissection – where a tear occurs in the inner layer of the body's main artery – and he was transferred to Queen Elizabeth Hospital for further treatment.

He underwent surgery, but suffered severe heart failure afterwards. At one point, he also experienced respiratory failure and required an artificial lung to help with breathing.

"The HA appeals to members of the public to proactively support organ donations and consider donating the heart of a deceased relative to rekindle the lives of others," an authority spokesperson said.

"In view of the critical condition of the patient, in addition to proactively searching for a suitable heart locally, the HA will also initiate procedures to seek assistance from the mainland as soon as possible."