The third transcatheter aortic valve operation was due to start at Waikato Hospital this morning following two successful procedures yesterday.
The operations were the first of their kind in a New Zealand public hospital and involve replacement of the heart's main outflow valve with another one via the leg.
The procedure only requires a local anaesthetic and has a short recovery time.
Conventional aortic valve replacement by open-heart surgery is the procedure of choice, but requires general anaesthetic, has a long recovery time and can often be ruled out by pre-existing medical conditions.
Yesterday's operations were carried out on 79-year-old Tauranga woman Ramona Johnson and a second, 91-year-old woman.
Waikato District Health Board spokeswoman Mary Anne Gill said two more operations would take place today and there was a chance a third could also take place.
The recipients were all from the Waikato, Bay of Plenty and Gisborne areas.
Ms Gill said surgeons took their time with the historic first operation yesterday and it had gone well.
Only about 2000 transcatheter aortic valve implementations have occurred worldwide - all in the northern hemisphere.