A broken heart is most often associated with unrequited love or a painful bereavement, but according to new research, happiness can have the same effect. Scientists have found that happy events in our lives can trigger a rare heart condition known as takotsubo syndrome (TTS), characterised by a temporary weakening of the heart's muscles.

Takotsubo syndrome is more informally known as 'broken heart syndrome', and it causes the left ventricle of the heart to balloon out at the bottom while the neck remains narrow. Since its discovery in 1990, research has typically linked it to episodes of severe emotional distress, such as grief, anger, and fear. Sufferers develop chest pains and breathlessness, and the condition can eventually lead to a heart attack or death. 

A team from the University Hospital Zurich in Switzerland looked at 1,750 registered TTS patients - the largest pool of data available on the condition - and found that some people developed broken heart syndrome after a happy or joyful event. Of the 485 cases where TTS could be linked to an emotional trigger, there were 465 instances (96 percent) where the trigger was sad and stressful, and 20 instances (4 percent) where it was more positive.

These happy event triggers included birthday parties, weddings, celebrations, victories in sport, and new births; the sad events included the deaths of a loved one, attending funerals, accidents, worries over illness, and relationship problems. One incident occurred after an obese patient got stuck in the bath.

"We have shown that the triggers for TTS can be more varied than previously thought," said one of the researchers, Jelena Ghadri. "A TTS patient is no longer the classic 'broken hearted' patient, and the disease can be preceded by positive emotions too. Our findings broaden the clinical spectrum of TTS. They also suggest that happy and sad life events may share similar emotional pathways that can ultimately cause TTS."

Ghadri suggests that doctors should take the new findings into consideration when dealing with patients reporting chest pains and breathlessness, because even if there are no sad or stressful events involved, TTS could still be the cause. In both the sad and happy groups, TTS was found to be more common in women and older people, confirming that the majority of TTS cases occur in postmenopausal women.

Now the team wants to see further studies looking at the underlying mechanisms that trigger takotsubo syndrome. Christian Templin, one of the scientists working on the study, said he believes TTS is "a classic example of an intertwined feedback mechanism" involving psychological and physical stimuli together. It's possible that both happy and sad events trigger a similar response in the central nervous system, he said.

The study has been published in the European Heart Journal.