A medical scan can spot which young people risk sudden death because of a weak heart.
Professor Pennell believes the scan could save lives
The scan shows up heart scar tissue, giving doctors an important warning sign of dilated cardiomyopathy or DCM, which can otherwise go undetected.
In DCM the heart becomes weakened and enlarged, and cannot pump blood efficiently.
It is the most common form of heart muscle disease at any age and many of those who die are children.
The new technique, developed by cardiologists at Royal Brompton Hospital, involves injecting a dye called gadolinium into the patient's vein and then scanning them using MRI (Magnetic Resonance Imaging).
The gadolinium stays around in the scar tissue more than in the surrounding tissue because scar tissue has a lower blood supply than normal tissue.
And gadolinium's special magnetic properties makes the scar tissue appear brightly on the scan and very easy to detect.
The Royal Brompton team tested the technique on 101 patients with and without scar tissue and followed them for two years to determine the effect of scar tissue on the patients' health outcomes.
By detecting the scar tissue, the researchers found they were better able to determine the risk of hospitalisation or death.
In turn, this enabled them to ensure patients received timely and appropriate care.
Some could be treated with drugs alone, while others required a £12,000 heart implant.
In the study, the scar tissue occurred in about a third of patients with DCM.
These patients were three times more likely to be hospitalised or die suddenly.
Lead researcher Professor Dudley Pennell said the scans should help guide important treatment choices.
He explained: "Prior to this technique it was difficult to decide which patients could be treated effectively using drugs alone, and which patients needed life-saving devices implanted.
"It is a costly and wasteful exercise to implant all patients with DCM when only 20 or 30% may truly require it."
Professor Peter Weissberg, medical director of the British Heart Foundation, which gave funding to the research, said: "This is an important advance that will help doctors prevent lives being lost to the condition."