The royal palace said the surgery was successful and his condition was described as good.
Following the op at Rikshospitalet’s Cardiovascular and Lung Clinic, King Harald V was transferred to an intensive care unit for further observation, his doctor, Bjoern Bendz, said in a palace statement.
Dr Bendz said the intervention was necessary to improve the king’s breathing, and added that this kind of operation is regularly performed.
Last month, the king was admitted to hospital with breathing difficulties, but doctors ruled out Covid-19.
After Friday’s surgery, the palace said he will be on sick leave through October.
His son and heir to the throne, Crown Prince Haakon, has stepped in and taken over his father’s duties.
The palace said the operation was not open heart surgery and that the king was awake during the the procedure, which was performed via the groin with local anaesthesia.
In 2005, the king’s aortic valve was replaced with an artificial valve. Such valves have a lifespan of 10 to 15 years, the royal household had said.
