Almost 300,000 people in Britain could have a potentially deadly heart valve disease, a new study suggests.
This includes almost 100,000 who have the condition but do not know it.
Researchers said the NHS is currently not equipped to deal with the scale of the problem, which could get worse with a growing number of elderly people in society.
Aortic stenosis is a heart valve disease which carries a high death rate if left untreated.
It occurs when the main valve which takes blood from the heart stiffens and narrows.
Many people do not know they have the disease and only discover they are afflicted when it is too late for treatment.
An international team of researchers, including experts from the Universities of Glasgow and Southampton, set out to research the extent of the disease in the UK.
Their study, published in the journal Open Heart, estimated that in the UK in 2019 there were 291,448 men and women aged 55 and over with severe aortic stenosis.
Of these, an estimated 68% would have symptoms.
This means an estimated 92,389 people have the disease and do not know it.
The authors went on to estimate that more than 172,000 (59%) who have the disease will â€˜die within five years without proactive managementâ€™.
They concluded that aortic stenosis is a â€˜common conditionâ€™ in the UK but warned that â€˜without appropriate detection and intervention, survival prospects are likely to be poorâ€™.
An estimated 20,000 new patients could benefit from treatment each year, but the researchers said this figure is â€˜discordant with current capacity within the NHSâ€™.
â€˜These data suggest a high burden of severe aortic stenosis in the UK requiring surgical or transcatheter intervention that challenges the ongoing capacity of the National Health Service to meet the needs of those affected,â€™ they wrote.