Dying of a broken heart sounds like the ending of a romantic story.

But it actually happens.

The "broken heart syndrome," usually affects people who have received very bad news.

Recently however, researchers discovered that even joyful events can kill you.

"Broken heart syndrome" is officially called Takotsubo syndrome, or TTS. It involves the sudden weakening of heart muscles. This weakening causes the left ventricle to expand abnormally at the bottom. If you remember from health class, the left ventricle is the chamber of the heart that pushes oxygen-rich blood through the body.

The symptoms of Takotsubo syndrome are acute chest pain and shortness of breath. The syndrome can lead to heart attacks and death.

Even though Takotsubo syndrome is fairly rare, the scientific community has studied how unexpected emotional shocks can cause a heart attack. These shocks are usually unpleasant, such as the death of a spouse or a violent argument.

However, no one had ever investigated whether an extremely happy event could give the same result.

Until now.

In 2011, a pair of researchers in Switzerland set up a global registry to track cases of the syndrome. Christian Templin and Jelena Ghadri are both with University Hospital Zurich.

Five years later, their registry involves a network of 25 hospitals spread across nine countries. They had collected data on 1,750 cases of the Takotsubo syndrome. This number of cases -- 1,750 -- is said to be "statistically significant" by scientific communities.

For the study, Templin and Ghadri led a team of 16 researchers. The team found that emotional shocks caused 485 of those 1,750 cases. And within that group of 485, a total of 20 people could be said to have suffered from "happy heart syndrome."

In an interview, Ghardi said that the researchers have shown that the causes for TTS are more varied than previously thought. The disease can be caused by positive emotions, too.

The events that caused the 20 cases of "happy heart syndrome" include a birthday party, a wedding, a surprise farewell celebration, a favorite team winning a game, and the birth of a grandchild. However, none of these cases of "happy heart syndrome" caused death.

Ghadri and her team published their findings in the European Heart Journal.

So what is the important take-away from this study?

Emergency room doctors should be aware of the fact that patients with signs of heart attack could be suffering from TTS. And these TTS cases could be caused by either positive or negative experiences.

Another interesting take-away is that TTS affects mostly women.

For reasons the researchers do not yet understand, 95 percent of the patients in both the "broken heart" and "happy heart" groups are women. These women are mostly in their mid- to late-60s.

Ghadri said she and her team still do not know why women are mostly affected by the Takotsubo syndrome.

The fact that more women than men are affected by Takotsubo syndrome is even stranger when you consider that heart attacks are more common among men.

The researchers suspect that the hormone estrogen may play a part in how the disease operates. Women have much higher levels of estrogen than men. In men, testosterone is the dominant hormone.

Happy and sad life events are, of course, very different. Further studies are also needed to figure out if both events share the same pathway in the central nervous system for causing Takotsubo syndrome.

Japanese researchers discovered the condition. They named it after a traditional Japanese octopus trap. An enlarged heart suffering from Takotsubo syndrome looks like an octopus trap.

I'm Anna Matteo.

Anna Matteo wrote this story for Learning English based on a report in the Japan Times as well as OxfordJournal.com where the study was published. Kathleen Struck was the editor.