Heart disease is the leading cause of death for both men and women in the United States. The relationship between stress, heart disease and sudden death has been recognized since antiquity. More research is needed to determine exactly how stress contributes to heart disease.

But what about the stress of a "broken heart"? Broken heart syndrome is a temporary heart condition that may be brought on by stressful situations, such as the death of a loved one or the end of a romantic relationship.

People with broken heart syndrome may have sudden chest pain or think they are having a heart attack. In broken heart syndrome, there's a temporary disruption of the heart's normal pumping function, while the remainder of the heart functions normally or with even more forceful contractions.

Now, new research suggests happy events can trigger a heart condition known as takotsubo syndrome, (TTS), also known as "broken heart syndrome." TTS is characterized by a sudden temporary weakening of the heart muscles that causes the left ventricle of the heart to balloon out at the bottom while the neck remains narrow, creating a shape resembling a Japanese octopus trap, from which it gets its name.

Since this relatively rare condition was first described in 1990, evidence has suggested it is typically triggered by episodes of severe emotional distress, such as grief, anger or fear, with patients developing chest pains and breathlessness, which can lead to heart attacks and death.

In this study, researchers systematically analyzed data from the largest group of patients diagnosed with TTS worldwide and found that some patients had developed the condition after a happy or joyful event; they named this condition "happy heart syndrome."

In 2011, Dr. Christian Templin, principle investigator and consultant cardiologist, together with Dr. Jelena Ghadri, resident cardiologist, established the first International Takotsubo Registry at the University Hospital Zurich in Switzerland. For this study, they analyzed data from the first 1,750 patients registered from the 25 collaborating centers in nine different countries.

The researchers found 485 patients who had a definite emotional trigger. Of these, 20 (4 percent) had TTS that had been precipitated by happy and joyful events, such as a birthday party, wedding, surprise farewell celebration, a favorite rugby team winning a game or the birth of a grandchild. The remaining 465 (96 percent) had occurred after sad and stressful events, such as death of a spouse, child or parent, attending a funeral, an accident, worry about illness or relationship problems.

Ninety-five percent of the patients were women in both the "broken hearts" and "happy hearts" groups, and the average age of patients was 65 among the "broken hearts" and 71 among the "happy hearts," confirming that the majority of TTS cases occur in post-menopausal women.

The study illustrates that TTS can be triggered by not only negative but also positive life events. While patient characteristics were similar between groups, the midventricular TTS type was more prevalent among the "happy hearts" than among the "broken hearts."

According to Ghadri, the new findings should lead to a paradigm shift in clinical practice because the study suggests triggers for TTS can be more varied than previously thought. A TTS patient is no longer just the classic broken-hearted patient, and the disease can be preceded by positive emotions, too.

Clinicians should be aware of this and also consider that patients who arrive in the emergency department with signs of a heart attack after a happy event or emotion could be suffering from TTS just as much as a similar patient presenting after a negative emotional event. Despite their distinct nature, happy and sad life events may share similar emotional pathways.