Jemma Benjamin, 18, of Cardiff, Wales, shared a first kiss with her new boyfriend before entering his apartment.
Then, minutes later, Benjamin collapsed on a sofa and died.
Her sudden death shocked her boyfriend and her family, who said that Benjamin, a University of Wales Institute student, was a star swimmer and hockey player who never showed any signs of health problems.
Even an autopsy could not point to a cause of death, according to Britain's Daily Mail. The Daily Mail said medical examiners ruled the likely cause of death may have been a hidden heart rhythm disease that brought on Sudden Arrhythmic Death Syndrome, or SADS.
"This kiss might have been an adrenaline generating experience," said Dr. Michael Ackerman, director of the long QT syndrome clinic at the Mayo Clinic in Rochester, Minn. "High excitement, deep sadness, extreme emotions or strenuous physical activity can be a trigger that can unmask these conditions."
In fact, many people may unknowingly have SADS, an umbrella term for a group of genetic conditions that abnormally affect a heart's rhythm.
"When there's a sudden unexplained death, albeit with a very bizarre trigger, it all hinges on the autopsy," said Ackerman. "The best way to find out is to do a postmortem genetic testing to search for a genetic flaw."
Many people may live their whole lives without triggering an abnormal episode, while others may experience fainting spells or seizures beginning at a young age, said Ackerman.
According to the Sudden Arrhythmia Death Syndromes Foundation, nearly 1 in 2,000 people in the U.S. suffer from any one of a range of genetic heart rhythm conditions. The most common form of SADS is long QT syndrome, a condition in which there are longer intervals between heart beats. Many younger children never have electrocardiograms, or ECG screening, which is designed to detect abnormal heart rhythms. And for those who have more subtle cases, an ECG may not be accurate enough to detect an abnormality, said Ackerman.
"The conundrum that we have is that about half of the patients who have this potentially lethal but highly treatable syndrome will never show it," said Ackerman.
While it may seem as if SADS can only be detected after death, Ackerman said, many may experience early warning signs that can help identify an abnormality.
One of the most common, he said, is sudden fainting not brought on by any trigger.
"That kind of faint has to be viewed as a warning faint, and that's a very important warning sign," said Ackerman. "It's unlike getting up too quickly, or getting queasy after you've had a blood drawn. It's really emphasizing an out-of-the-blue faint."
Four years ago, Annie Lucatuorto, 14, of Long Island, N.Y., was at a swimming lesson when she fainted in the pool.
"I was doing a few strokes and when I got to the edge I fainted. But I felt perfectly normal, I barely even knew what happened," said Annie.
Doctors at the hospital diagnosed Annie with long QT syndrome and placed her on daily medication to regulate her heart rhythm. They also told her that she could no longer participate in strenuous sports like soccer, which she had played since she was four years old.