Surgeons in Swansea have taken delivery of an ultrasound probe that produces three-dimensional images of the heart.
The ultrasound probe can be placed on a patient's beating heart
The probe, one of few of its kind in the UK, was bought by Morriston Hospital using donated money.
It can be used in open-heart surgery to enable surgeons to see real-time 3D images of a patient's beating heart on a computer screen.
They describe the 3D images from the £60,000 machine as "like being able to take a walk inside a patient's heart".
Consultant cardiologist Adrian Ionescu said: "The quality of the pictures is unparalleled, as there is no intervening structure between the probe and the heart.
"This is not experimental, but it's certainly very, very new and hardly done in the UK."
He said the probe would make a "significant difference" for some patients with complex heart problems.
He said: "Say you have a patient with a complex problem such as a rupture of the heart wall following an extensive heart attack. When this complication isn't fatal it requires immediate surgery.
"The surgery is very difficult because often these ruptures occur in an area of the heart which the surgeon has great difficulty to see, even on a non-beating open heart.
"Being able to look at the heart while it's still beating, with 3D, can allow a significant advantage in planning the operation and making it a success.
"Basically, in this type of situation, you have one go and if you don't get it right, the likelihood of having a live patient at the end is very low.
"This is one of the rare but nevertheless very significant situations where this technology is likely to make a major impact."
The hospital's cardiac unit has so far used the probe with around 15 patients, and is currently assessing early data with a view to publishing their findings later this year.
The probe and equipment were bought with money donated to Swansea NHS Trust by the late Reverend David Albert Williams, of Llanwrda.