Boston - People of African descent can have a gene that makes them prone to potentially lethal irregular heart rhythms, say researchers.
Europeans and Asians do not appear to have the gene. It is also occurs rarely among people of Hispanic origin.
A team of United States and British scientists worked out that people with the "Y1102" variation of a certain heart gene were eight times more likely than normal to have irregular heartbeats, or arrhythmia.
Usually arrhythmia is the result of a heart attack or other heart condition, but sometimes it can happen spontaneously.
The gene variant was identified by comparing DNA samples between individuals, the researchers reported in the journal Science.
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Many with irregular heart rhythms had the Y1102 variation in a gene that encodes part of the channel regulating the flow of sodium in and out of heart muscle cells.
Among a control group of people without arrhythmia, the gene variant was seen in 19,2 percent of people from West Africa and the Caribbean, in 13,2 percent of African Americans, in no Caucasians or Asians at all, and in just one of 123 Hispanics.
A study of 23 African-Americans with arrhythmia and 100 healthy African-Americans showed that the gene variant was disproportionately common among those with irregular heart beats.
The researchers also studied the extended family of one African-American with arrhythmia. Out of 23 family members, 11 had related heart irregularities, all of whom had the gene variant.
Dr Mark Keating of Harvard Medical School in Boston, who was involved in the study, said: "We've identified one variant, which is one piece in a huge puzzle. But every time we can identify a piece, we can use that information to reduce risk, which is already quite low for an individual at any given moment."
The gene variation does not cause an irregular heart beat on its own, the researchers reported in the journal Science. It was thought to affect people lacking enough electrolytes - potassium, calcium, sodium and magnesium - in their blood.
Certain drugs reduce electrolyte levels, as does physical exercise. "It's important to make sure that serum electrolytes stay normal," said Dr Keating. "We do things all the time that make them abnormal, such as taking diuretics, or running marathons." - Sapa-DPA
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