Describing it as "one of the new frontiers in heart science", experts behind the ground-breaking treatment said that the gene could restore proper pumping function to failing hearts, halving the risk of mortality or need for heart transplants.
If proven to work, the researchers hope that it will be available for widespread use within eight years.
British Heart Foundation (BHF) medical director Professor Peter Weissberg said that while drugs can offer some relief, there is no way of restoring function to the heart, the Daily Express reported.
However, the early clinical study is the culmination of years of BHF-funded laboratory research and offers real promise, he said.
He asserted that gene therapy is one of the new frontiers in heart science and is a great example of the cutting-edge technologies that the BHF is using to fight heart failure.
The gene has the potential to reverse some of the molecular damage brought on by a cardiac arrest, alcohol, disease or infection.
Once the damage is done, heart failure soon occurs - heart becomes too weak to pump blood efficiently around the body, leading to breathlessness and exhaustion.
It is believed that the treatment will be priced just a few hundred to a few thousands pounds per person, a fraction of the 200,000 pounds cost of each heart transplant.
The Cupid 2 trial - following an earlier Cupid 1 trial in America - is taking place in conjunction with US biotech company Celladon that has patented the treatment.
A second trial is to start recruiting this summer will look at the gene's effect on patients form UK, who are fitted with mechanical pumps.