Scientists believe they may have discovered the cause of a form of heart disease that is passed on from generation to generation.
DCM affects 35 in every 100,000 people
Researchers in the United States have suggested a gene defect may trigger dilated cardiomyopathy (DCM).
This condition occurs when the heart becomes so enlarged that it is no longer able to pump blood efficiently.
It affects about 18,000 people in Britain and about twice as many men as women.
Scientists at the Howard Hughes Medical Institute in Maryland discovered that some people with inherited DCM show a subtle mutation in their phospholamban gene.
This gene plays a key role in regulating the flow of calcium through the heart, enabling it to beat effectively.
The heart muscle contracts and relaxes when calcium is released from a reservoir inside into the muscle cell and then pumped back quickly.
The scientists used tests on mice to determine whether a defect in this gene is enough to trigger DCM.
They found that a mouse with a defect on the phospholamban gene also suffered severe damage to its heart.
Further laboratory tests showed that this defect disrupts the calcium pump in heart muscle cells.
The scientists found that people with this defect would suffer a chronic malfunction of calcium regulation in their heart muscle. Over time this would lead to heart failure.
They believe that the discovery could help in the development of new drugs to treat the condition.
But they also believe it could help scientists to understand more about heart failure.
"Our treatment of heart failure is, in this day and age, relatively non-specific," said Christine Seidman who led the study.
"The kind of molecular dissection of the cause of heart failure that we have done leads us to ask whether if we can restore calcium cycling in this type of defect, can we prevent heart failure. The hope is that the answer will be yes."
But she added: "There are pieces of this puzzle that are starting to come together to fit a profile of a group of patients who we think would very much benefit from modulating calcium homeostasis in heart cells."
Patients with DCM may suffer with tiredness, and shortness of breath whilst exercising or even whilst resting. They may have heart palpitations and notice their ankles becoming swollen.
DCM is not a common condition. For every 100,000 people around 35 people will have it.
The study is published in the journal Science.