A new national fast-track laboratory is aiming to offer definitive explanations of sudden cardiac deaths in people under the age of 35 within a few weeks.
The heart is taken for tests
In the past some families have had to wait up to 18 months to find out why a young family member has died.
Coroners have been informed about the expert cardiac pathology laboratory at Royal Brompton Hospital, in London.
They are urged to refer complicated cases to the service, which is funded by charity Cardiac Risk in the Young.
Experts say the service could also save lives by identifying other family members with the same heart conditions.
The cash donated by the charity will enable consultant histopathologist Dr Mary Sheppard and her team to focus specifically on complex cases.
In the past, difficult cases have sometimes taken months to resolve because they have been processed by coroners already swamped with work and by non-dedicated specialists.
In some cases, deaths have been recorded as unascertained or incorrectly put down to something else.
Dr Sheppard hopes the service will provide some sort of closure for grieving families.
She said: "This is horribly traumatic for the families and a delay with diagnosis means more trauma for them.
"My staff can look at the heart very quickly and give a result in two weeks and a pathological report on the cause of death.
"They need to be aware of what the cause is and whether there is a family link, because some of these diseases can be genetic.
"The importance is getting a right diagnosis for family screening."
Alison Cox, chief executive and founder of Cardiac Risk in the Young, said the fast-track service was "long overdue".
"For years we have been frustrated by the time it takes for families to get answers about their tragedy, which happens without warning or explanation," she said.
"Coroners sometimes do not have the funds or know how to access a service where they can refer complex cases to an expert pathologist, meaning that many deaths are simply recorded as unascertained or, incorrectly, as an accident such as epilepsy, asthma or drowning.
"This is unacceptable for grieving families and leaves surviving relatives at risk of further tragedies as these are genetic conditions and other family members need to be screened.