Katie Nicholas, of Stourton Avenue, will attempt to set a new Guinness World Record for the fastest marathon dressed as a love heart (female).
She needs to complete the 26.2-mile course in under four-and-a-half hours to set the record but is aiming for a four-hour finish.
So far she has raised more than £2,000 for Cardiomyopathy UK thanks to family, friends, fellow members of Twickenham Rowing Club and colleagues at BP, which has promised match funding up to £5,000.
The 29-year-old, who will run the marathon for the third time, said: “The charity is really important to me. As with many other sufferers, the disease went undiagnosed until it made a sudden and distressing appearance in my friend’s mother who had previously appeared extremely fit and healthy. Then it was diagnosed in my friend.
“As I’ve competed in the London Marathon twice before I thought I should make it harder on myself to really earn my sponsorship.
"So given my chosen charity, I thought running it in a heart costume I have made myself would be fitting.
“I’ve been out training in it and while it’s not too restrictive, I know on the day I’m going to be super-hot.”
Cardiomyopathy is a heart muscle disease which affects people of all ages, is usually inherited and is one of the main reasons for young people dying suddenly.
The charity formerly known as Cardiomyopathy Association provides information and support to affected families affected by the heart disease as well as educating medical professionals about the disease and best treatments.
Katie's record attempt has been registered with the official Guinness World Records and her costume approved.
The organisation will be officially adjudicating her attempt on the day.
Sponsor Katie at www.justgiving.com/RunningHeart.