Thalassaemia is a disorder of the haemoglobin protein which gives red blood cells their colour
UK experts say they have found a way of predicting which thalassaemia patients are going to develop heart failure.
The technique uses a magnetic resonance scanner to measure the level of iron in the heart, which builds to life-threatening levels in some patients.
The study, published in the journal Circulation, suggests the technique leads to a 71% reduction in deaths.
Thalassaemia is an inherited disorder of the blood system which causes a lack of haemoglobin.
A government spokesman said it could significantly help in the management of people with thalassaemia.
The teams at the Royal Brompton Hospital and Imperial College tried the technique on 652 patients over seven years.
Haemoglobin is a protein contained in red blood cells which takes oxygen from the lungs to the rest of the body.
A lack of oxygen can cause breathlessness, lethargy and fainting - a condition known as anaemia.
People with thalassaemia may have to have two or three blood transfusions a month.
Each time they receive about 250 milligrammes of iron in the blood and daily drug treatments to try to remove the iron from their body - a normal daily intake of iron from the diet is 30 milligrammes.
Despite this, in 50-60% of patients there is a potentially life-threatening build up of iron levels.
The iron is deposited as tiny specks of rust (ferrihydrite) in the cells of the heart.
When a scan is taken the rust causes the signal to wobble and break up.
The more rust there is, the darker the scanned picture and the scientists have created a scale (cardiac T2*) which shows them which patients have so much iron they are going to have heart failure.
They can also use the scan to show them which drugs are best at removing rust from the body.
Professor Dudley Pennell, director of heart assessment at the Royal Brompton Hospital, said: "The data unequivocally demonstrates that cardiac T2* is a powerful predictor of the subsequent development of heart failure.
"T2* is really the penicillin of the thallassaemia world - penicillin saved so many lives and T2* is going to do the same."
The cardiac T2* technique has already been implemented in at least 50 centres around the world.
Roger Boyle, the National Clinical Director for Heart Disease and Stroke in England, said: "I am delighted to welcome this important piece of research which will significantly help us to manage the care of the people who live with thalassaemia."