There has been a dramatic rise in the number of people waiting for a heart transplant in the past twelve months, according to the NHS.
The waiting list has gone up by a quarter since last Christmas, with the current list including 33 children.
The situation has led to NHS Blood and Transplant to call out to the public to join the organ donor register.
Most patients on the heart transplant waiting list have already exhausted all other medical options; 31 people have died while on the waiting list for a heart transplant in the past year.
Those who do receive a heart transplant can expect to live on average for a further 14 years on average.
There are some 298 people currently on the list compared to 240 people at the same time last year - a rise of 24%.
"Hundreds of people are spending Christmas waiting for a call that might never come. Their families will be spending the festive period living with fear and uncertainty,” said Sally Johnson, NHS Blood and Transplant director of organ donation and transplantation.
"We desperately need more people to agree to donation to help with the number of people waiting for hearts and organs of every kind. Whatever the outcome of the Opt Out consultation, if you support organ donation, please act today.
"Tell your family you want to donate and join the NHS Organ Donor Register."
Steven Tsui, consultant cardiothoracic surgeon at Papworth Hospital NHS Foundation Trust and chairman of the NHS Blood and Transplant Cardiothoracic Advisory Group, said: "The UK heart transplant waiting list has been growing year on year.
"A lot of people who could donate do not discuss their wish to be an organ donor with families and friends. When they die, their organs simply go to waste.
"Heart transplant is the most amazing treatment for patients with advanced heart failure. The transformation is quite miraculous.
"On average, a heart transplant recipient can expect to live for another 14 years; the lucky ones could even get 25 or 30 extra years."