Doctors are trying to find out why Cameroon international footballer Marc Vivien-Foe died from a heart attack at the age of 28.
Marc Vivien-Foe died while playing for his country
However, an underlying heart defect such as "long QT syndrome" will be high on their list of suspects.
Sudden Adult Death Syndrome (SADS), has been described by some experts as the adult version of cot death in infants.
They believe that many cases may be caused by heart arrhythmias - when the heartbeat races without warning.
This can cause fainting - or in very rare cases - collapse and death even in very young adults.
Long QT syndrome
Many of these arrhythmias are also described as Long QT Syndrome, a particular disorder of the electrical system of the heart.
The problem centres on the length of time it takes the electrical system to recharge following a heatbeat. This is known as the QT interval.
People who have a long QT interval are more vulnerable to a very fast, abnormal heart rhythm.
When this rhythm occurs, no blood is pumped out from the heart, and the brain quickly becomes deprived of blood causing sudden loss of consciousness and sudden death.
Long QT syndrome is inherited in some cases, and many experts say that the high risk of a fatal arrhythmia brought on by exercise means that all young athletes should be screened for it.
Heart tests can detect the condition
Those who are diagnosed as having it should not take part in competitive sport, it has been suggested.
However, it is not just during strenuous exercise that a fatal arrhythmia can strike.
Sudden death can often occur when the victim is asleep, or when they are waking up.
Not all patients who have this condition have any symptoms - about one-third never develop any.
In the other two-thirds, some have just one or two fainting spells as children.
Hard to find
It is not an easy condition to spot, especially on a routine heart health check of the type normally given during a footballer's medical.
The subtle clues to Long QT syndrome may be absent entirely during a single scan.
However, when a doctor is looking specifically for Long QT, monitoring the heart rhythm over a longer period, the telltale signs can be picked up.
Scientists do not know exactly how common Long QT is - there are a lot of undiagnosed cases out there.
Patients identified as being at risk can be given drugs known as beta-blockers to slow heart beat.
Other drugs can be used for patients who have a specific form of the disorder.
Once treated, it is very important that the medication be taken every day and not missed or omitted.
The medications are not curative - they only provide protection while being taken and the protecting effect is gone within a day or two of stopping the medication.
There are other heart conditions, which, if left untreated, can precipitate a fatal attack even at a young age in an apparently healthy adult.
Another footballer, Kanu, who now plays for Arsenal, had a heart valve problem which, doctors said, could have caused a heart attack on the field of play.
He received surgery to fix the problem at the age of 20, and has had no problems continuing his career at the highest level.