LONDON (Reuters) - A 37-year-old British man who needs a mechanical pump to keep his heart working has kicked off tests to see if gene therapy could help him recover and potentially avoid the need for a heart transplant.

U.S. biotech firm Celladon hopes that its Mydicar treatment can help patients like Lee Adams who have advanced heart failure and rely on so called Left Ventricular Assist Devices (LVAD) to keep them alive until a donor heart becomes available.

Celladon's treatment works by inserting a gene called SERCA2a - the lack of which makes hearts pump weakly - directly into heart cells via a catheter to repair them. The trial will evaluate how much of the gene is getting to the heart muscle and how well it is working.

Adams, from Hertfordshire, north of London, is the first of 24 patients with heart pumps who will be given either the gene therapy or a placebo as part of a clinical study partially funded by the British Heart Foundation and sponsored by Imperial College London.

"Advanced heart failure is a progressive condition that results in a poor quality of life and shortened life expectancy," said Dr Nick Banner, the consultant cardiologist at Harefield Hospital who carried out the first infusion.

"The best treatment currently available is a heart transplant but the shortage of donor organs in the UK means that many patients will die on the transplant waiting list."

Adams is on the waiting list and has been living for more than two and a half years with an LVAD, which must always be connected to an external power supply via a lead through his abdomen.

"You can't just jump in the shower...and it's difficult sleeping whilst being attached to it. Everywhere I go I have to carry the power supply and spare batteries in a backpack," he said.

"Of course the best thing that could happen would be...for the gene therapy to prove to be a 'miracle cure' for myself and other patients."

Plans for the study were first announced last year and complement an ongoing 250-patient trial, also funded by Celladon, which is investigating the benefits of gene therapy in 250 people with less advanced heart failure from Europe and the United States.

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That trial is expected to report results next year.

The success of the experimental Mydicar gene therapy program is critical to Celladon, which listed on the United States' Nasdaq stock market in January. Mydicar is the company's most advanced product.

(Reporting by Ben Hirschler; Editing by Sophie Walker)