London, Aug 2 (IANS): Researchers have found that patients with congenital heart defects often inherit the disease from their healthy parents.

Congenital heart is one of the most common developmental defects, occurring in 1 per cent of the population world-wide and affecting 1.35 million new-borns every year with problems like holes in the heart as well as causing life-long disability to many.

Previous studies have found that the rare heart disease might be caused by spontaneous new mutations which are present in the child and absent in the parents.

The findings confirmed that patients with the rarer syndromic congenital heart disease -- with additional developmental problems like abnormalities in other organs or an intellectual disability -- often had spontaneous new mutations likely to interfere with normal heart development that were not seen in the parents.

However, it also showed that non-syndromic congenital heart disease patients -- around 90 per cent with only isolated defects in heart -- did not have such spontaneous mutations.

The study for the first time conclusively showed that they often inherited damaging gene variants from their seemingly healthy parents, the researchers said.

"This is the first study to quantify the role that rare inherited variants play in non-syndromic congenital heart disease, and is extremely valuable as these patients make up 90 per cent of congenital heart disease patients worldwide," said lead author Mathew Hurles, Wellcome Trust Sanger Institute - a non-profit research institute in Cambridge, Britain.

"We now know that some of the causative factors of the disease are inherited from healthy parents. This will be extremely helpful for designing future studies of non-syndromic congenital heart disease, helping to understand what causes the disease," said Marc-Phillip Hitz, Wellcome Trust Sanger Institute.

For the study, published in the journal Nature Genetics, the team sequenced and analysed the protein-coding segments of the genome - known as the exome - of 1,900 congenital heart disease patients and their parents.

They found three new genes in which mutations can cause rare syndromic congenital heart disorder.

"As a direct result of this research, doctors may be able to offer much clearer advice to families where one member has congenital heart disease," noted Jeremy Pearson, Professor and Associate Medical Director at the British Heart Foundation.