Currently, hearts from donors over 65 years old are not used for donation due to the expected negative outcome.

But experts have suggested that age alone does not necessarily determine heart health as hearts age differently.

Newcastle University researchers are currently developing a test that could assist doctors in assessing the viability of a donor heart for transplantation quickly.

There are roughly 320 individuals in the UK awaiting a crucial heart transplant as of today.

Fortunately, a newly developed test could potentially raise the number of available organs and offer hope to more patients in need of transplants.

The research, which received partial funding from the British Heart Foundation, was presented to attendees at the British Cardiovascular Society conference in Manchester.

The study reveals that individuals with heart disease exhibit a higher quantity of senescent cells, also known as "zombie" cells, than those without the condition. This was confirmed by elevated levels of "zombie" cell markers found in their blood samples.

While these "zombie" cells are not dead, they do not operate as they should.

They generate molecules that can influence and transform the cells around them into "zombie" cells too. This condition can potentially promote inflammation and lead to the accumulation of scar tissue in the heart, which heightens the likelihood of contracting cardiovascular diseases.

In order to explore the physiological instead of chronological age of the heart, the researchers aim to delve further into the blood signature left by these "zombie" cells.

According to Dr Gavin Richardson, the senior lecturer and head of the vascular medicine and biology theme at Newcastle University, researchers are exploring the possibility of using a blood test to identify older potential donors with biologically young, healthy hearts that could be appropriate for transplantation.

He said: "Our work is revealing more about the clues that 'zombie' cells leave to suggest their presence in the body.

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"We are confident that we will be able to use these clues to better understand which hearts from non-eligible donors might be able to be used after all.

"This could be a game changer as currently most hearts from older donors are not used for transplant, but the hope is we will be able to show that a number of these organs are suitable for transplant for people desperately waiting for a new heart."

Researchers discovered that "zombie" heart cells secrete higher levels of a protein called GDF15 compared with healthy cells.

Using blood samples from over 774 people aged over 85, the study found higher levels of this protein in the blood of people with heart disease compared with those without, suggesting their hearts contain more "zombie" cells.

Professor James Leiper, associate medical director at the British Heart Foundation, said: "We are facing a heart failure epidemic with nearly one million people in the UK living with this condition and for a small but significant number of these people the only cure we can offer is a heart transplant.

"We urgently need more hearts available for transplant, so it is very encouraging to hear about the work Dr Richardson and his colleagues are doing to help meet this demand."