The centres of the brain responsible for learning, memory and emotion may play a key role in putting the heart under strain in times of stress.
The brain may increase stress on the heart
UK scientists have shown that signals from these areas can destabilise the cardiac muscle of someone who already has heart disease.
This, the research suggests, can trigger potentially fatal abnormalities in the heart's rhythms.
The study is published in Proceedings of the National Academy of Sciences.
It has long been known that stress triggers increased activity in the heart.
This is designed to maximise blood flow, so that the body is primed to take quick action.
However, it had been thought that this change was due to signals from more primitive areas of the brain.
In the latest study researchers at University College London and the Brighton and Sussex Medical School studied 10 patients with specific heart conditions.
Electrical changes at the surface of the skull were measured while the patients performed a mildly stressful task - counting backwards in sevens.
The results showed that activity in the 'higher level' regions of the brain, such as the cortex closely reflected the response measured in the heart.
The measurements also suggested that a "feedback loop" was established, with these centres reacting to information being fed back from the heart by pumping out more signals to increase activity.
Ultimately, this destabilised the heart muscle, raising the possibility of abnormal and potentially dangerous rhythms, which can cause sudden death in vulnerable patients.
Researcher Dr Marcus Gray said: "We found a close association between the actual performance of the heart and activity in the cortex, which suggests that these brain regions listen closely to the beat-to-beat activity.
"We know that stress can increase the risk of sudden death through cardiac arrest and that the brain areas responsible for regulating heart function can be unbalanced by stress.
"Our research suggests that the cerebral cortex may play a significant role in these events by becoming involved in a vicious circle."
Jeremy Pearson, of the the British Heart Foundation, said: "In future it may be possible to use the techniques in this study to identify in advance those patients whose hearts are more likely to have an adverse response to stress."