Children who see flashing lights during a migraine have twice the normal likelihood of having a hole-in-the-heart, a study suggests.
US doctors examined 109 children over six who were migraine sufferers.
About half of those with a type of migraine accompanied by a visual disturbance called an aura had the heart defect, the Journal of Pediatrics reports.
The British Heart Foundation called for further research into the link.
Amy Thompson, senior cardiac nurse at the British Heart Foundation, said: "There could be a number of explanations for this link so further research needs to be carried out before we draw any firm conclusions.
"Once we understand the relationship in more detail it could signal an improvement in patient care."
A number of medical studies have found a link in adults between a type of hole-in-the-heart - known technically as a patent foramen ovale (PFO) - and migraine with aura.
This has lead to attempts to treat migraine by surgery to close the hole, when other migraine therapies have failed.
Dr Rachel McCandless and colleagues of the University of Utah used a scanning technique known as an echocardiogram to look for the heart defect.
Of the children who had migraines with aura, 50% also had the defect. This is nearly double the rate seen in the general population.
She said she hoped "our study will help guide future research about this difficult problem".
Around one in 10 people have aura with their migraines.
Common aura symptoms include visual disturbances such as seeing flashing or flickering lights, numbness, tingling sensations and slurred speech.