THEY were walking time bombs. Members of a family with an inherited heart condition who knew at any time their hearts could stop pumping enough blood through their bodies, causing stroke, heart failure or death.
The condition, called dilated cardiomyopathy and usually incurable, affects about one in 2000 Australians and leaves the heart weak and enlarged.
But in a world first, Sydney researchers cracked the genetic code for one family suffering from the disorder, identifying a gene mutation that would have eventually left some in need of a heart transplant, or dead.
The Victor Chang Cardiac Research Institute led the project and collaborated with St Vincent's Hospital to screen 42 members of the family. Researchers found a rare mutation in the cardiac sodium channel among almost half of them.
Those affected were treated with a sodium channel blocker, a drug that already existed. The drugs are not usually recommended for patients with heart failure because of the potential side effects.
The institute's deputy director, Jamie Vandenberg, said it emphasised the importance of personalised medicine, since the gene mutation that caused the condition would not be the same in every family.
''The therapy we've devised is only appropriate for those with a defect in this particular gene, which would be in the very small percentages,'' he said.
''But about 40 per cent of people with dilated cardiomyopathy have a genetic cause for the condition and new technology is making it easier to identify those specific genetic causes. Depending on what particular gene defect is identified, if we're lucky there will already be a drug already available for it, as there was in this case, and if not we will at least know which genes we need to target.''
Targeting genes would not be an effective treatment in those patients for whom the cause was not genetic, he said. Infections, alcohol abuse and exposure to toxins were also thought to be responsible.
The study was published in the Journal of the American College of Cardiology and its lead author, Diane Fatkin, said even those patients with severe disease had returned to full health within six months.
''This is game-changing research,'' she said. ''Whilst we can only claim to have treated one particular mutation that causes cardiac dysfunction, and there is still much more to do to find the genetic causes of heart disease in every family, this is a huge step in the right direction.''
Dilated cardiomyopathy can affect people of all ages, from newborns to the elderly.