A pioneering trial has started to look at whether gene therapy can help the recovery of patients who are waiting for heart transplants.
Lee Adams, 37, a carpenter from Rickmansworth, Hertfordshire, is the first of 24 patients with advanced heart failure to be recruited.
Sixteen randomly chosen patients will be treated with a corrective gene to help their hearts beat more strongly.
Eight others are to receive a "dummy" placebo therapy.
Mr Adams does not know which group he is in because the trial is "blinded".
The trial, led by Imperial College London, has been funded by the British Heart Foundation (BHF) and Celladon Corporation.
Patients are being recruited from Harefield Hospital, London and Papworth Hospital in Cambridgeshire.
Like all the other participants, Mr Adams has been fitted with a mechanical pump to keep his blood flowing while waiting for a suitable donor heart.
The study claims to be the first in the world to investigate the use of gene therapy in heart failure patients kept alive by a left ventricular assist device (LVAD).
Mr Adams said: "Of course the best thing that could happen would be for my heart function to show signs of improvement and for the gene therapy to prove to be a 'miracle cure' for myself and other patients.
"But I'm not building up my hopes too much because, for all I know, I might have had the placebo."
The therapy involves injecting a harmless altered virus into the bloodstream to carry the corrective gene into heart muscle cells.
Six months after the treatment, biopsies of heart muscle will be taken to see if the gene is present and functioning.
The hearts of patients who subsequently have transplants will also be examined.