A team from Queen Mary University of London checked 10,000 one-year-olds for familial hypercholesterolaemia (FH).
Suzanne Sheppard, who has FH - and whose nine-year-old son also has it - said she would have "jumped at the chance" of testing him earlier.
But experts said more work was needed before such a programme was introduced.
FH is the main cause of early heart disease. If people with it do not take statins to lower their cholesterol, they have a 10-fold increased risk of a heart attack before the age of 40.
Suzanne, from Cardiff, found out her family was affected by FH after her father died of a heart attack at the age of 41 - when she was 15.
"They thought there may be something behind him having a heart attack at such a young age. So a few years on I was tested and found to have FH."
At the moment, testing works as it did for Suzanne. If an adult has heart problems and is found to have FH, others in the family are tested.
The study, published in the New England Journal of Medicine (NEJM) reversed the approach, and carried out heel-prick blood tests on children, with an average age of 13 months, to check cholesterol. and known genetic mutations linked to FH.
Forty children were found to be FH positive - and because one of their parents must also be affected by the genetic condition, it meant two people were diagnosed for each positive test.
The researchers say routine testing could prevent around 600 heart attacks a year among people under 40 in England and Wales.
Prof David Wald, who led the research, said: "It's the only screening method that stands a reasonable chance of covering the whole population and identifying those at highest risk of an early heart attack."
Suzanne's son Cameron was tested last year - aged eight.
But she said: "As soon as I had my test done and was identified, we always knew there was a 50% chance he would have it.
"He was 18 months old when I found out, and waiting all those years. I would have jumped at the chance of finding out. Not knowing is worse."
Cameron is now on a low dose of statins.
Suzanne said:"My thinking is, if you do it now when you have a relative amount of control, it's not going to be a consideration when he's a teen when that may be a bit more of a problem."
But the UK National Screening Committee, which looked at this issue in March this year, said questions remained about how a screening programme would work in practice, whether universal screening of one-year-olds would be effective, or if it would actually reduce illness and deaths associated with FH.
And Prof Sir Nilesh Samani, medical director at the British Heart Foundation (BHF), said: "Early diagnosis in children is likely to substantially improve treatment of their condition and will help find other family members with FH.
"But before nationwide screening is adopted by the NHS, more work needs to be done to show it's a cost-effective way for picking up individuals with FH which will be acceptable to families.
"Before any future change in practice based on this new research, the widespread rollout of the current cascade testing programme is vital if we're to prevent people unnecessarily dying from FH".