Hong Kong health authorities have opened an investigation into an alleged medical blunder involving an improperly sealed catheter that led to the death of a 75-year-old man following a heart procedure at Tuen Mun Hospital.

The Hospital Authority said on Thursday that the patient, who had a history of chronic obstructive pulmonary disease and high cholesterol, was admitted on Wednesday last week after his respiratory condition worsened.

His health deteriorated further following an acute heart attack, prompting doctors to schedule a percutaneous coronary intervention, a “balloon angioplasty” procedure used to widen obstructed arteries on Monday.

An authority spokesman said medical staff first noticed air bubbles via an imaging test during the surgery.

“They immediately checked the blood pressure monitoring device and other connection equipment, but found no abnormalities. The patient was stable at the time,” he said.

Staff proceeded with the surgery after a clinical assessment, but 30 minutes later, air bubbles were again detected in the patient’s coronary artery.