Being jilted really can break your heart, researchers in the United States revealed today.

They have discovered that sudden emotional stress can lead to severe but reversible heart muscle weakness which mimics the symptoms of a heart attack.

Patients with this condition, called stress cardiomyopathy or "broken heart syndrome", were often misdiagnosed with a massive heart attack, said the US researchers.

But instead these patients had actually suffered from a surge in adrenaline and other stress hormones that temporarily "stun" the heart.

Researchers from Johns Hopkins University in Baltimore, said that while "broken heart syndrome" was not as common as heart attack, it probably occurred more often than doctors realised.

Dr Ilan Wittstein said: "Our study should help physicians distinguish between stress cardiomyopathy and heart attacks. It should also reassure patients that they have not had permanent heart damage."

The researchers found that some people responded to sudden and overwhelming emotional stress by releasing large amount of stress chemicals like adrenaline into the bloodstream, as well as breakdown products and small proteins produced by an excited nervous system.

These chemicals could be temporarily toxic to the heart, effectively stunning the muscle and producing symptoms similar to a typical heart attack - chest pain, shortness of breath and heart failure.

By examining a group of 19 patients with symptoms of "broken heart syndrome" they discovered that, the researchers found that it was clinically very different to the typical heart attack.

The patients, 18 of whom were women, had signs of an apparent heart attack after emotional stress, including a death, shock from a surprise party and an armed robbery.

They were compared to seven other patients who had suffered a severe heart attack.

The researchers now expect the number of patients diagnosed with "broken heart syndrome" to increase as more doctors learn to recognise its unique clinical features.

Details of the study appeared in the latest edition of the New England Journal of Medicine.