A grandmother said she feels like a "new woman" after she was fitted with a wireless pacemaker smaller than a grain of rice.
Joan Smith, 71, from Marton, Middlesbrough, is the first woman in the world outside a clinical trial to be fitted with the revolutionary device.
The former lab worker and council receptionist was diagnosed with cardiomyopathy 21 years ago and underwent the operation in February at the James Cook University Hospital, Middlesbrough.
The grandmother-of-five, who had gone through two unsuccessful attempts with a conventional pacemaker, said: "I didn't feel any fatigue at all and it had been fatigue that I had been feeling previously - not breathlessness like some people experience.
"I feel as if I'm a new woman."
Doctors stabilised her with medication for 20 years but last year she was told she needed a pacemaker.
She was fitted with a new type called a WiSE pacemaker, made by EBR Systems.
It is thought that, like Mrs Smith, around 30% of patients fail to benefit from a conventional pacemaker, with wire failure the main problem.
The new wireless type is implanted directly into the innermost layer of tissue that lines the left chamber of the heart, where it is most beneficial.
Like a conventional unit, it controls abnormal heart rhythms using low-energy electrical pulses to prompt the heart to beat at a normal rate - but without the need for wires and the risk of complications that come with them.
Simon James, consultant cardiologist, said: "For Joan, as soon as the device was switched on there was a huge change in the pumping of the heart. Her blood pressure went up from the moment it was switched on so we felt confident she would begin to feel better quickly.
"The technology enables us to fit the device exactly where an individual patient needs it, which could increase the number of patients who respond to this therapy, helping them to live a longer, more active life."
During recent clinical trials of the device, patients whose conventional CRT pacemaker treatment had failed benefited from an 81% improvement in their condition.
This led to the device being approved for use in hospitals - with the James Cook University Hospital being the first to take advantage of the new type of treatment on behalf of three patients, including Joan, outside of a research study.