(HealthDay News) – Complex inheritance is usual in vasovagal syncope, with major autosomal dominance less common.

To examine the role of genetic factors in vasovagal syncope, Karl Martin Klein, MD, PhD, of the Epilepsy Research Centre at the University of Melbourne in Australia, and colleagues conducted a study involving 51 sets of same-sex twin pairs, between the ages of 9–69 years, where at least one twin had a history of syncope.

The researchers found that, for any syncope, there was a trend toward higher case-wise concordance in monozygous (MZ) than dizygous (DZ) twins (P=0.06). The effect on concordance was significantly different for MZ and DZ twins for fainting at least twice unrelated to external factors (P=0.018) and for syncope associated with typical vasovagal triggers (P<0.001). There were sparse or no family members affected in 12 of 19 concordant MZ pairs, while multiple close relatives were affected in the other seven pairs.

“The twin analysis provides strong evidence for the relevance of genetic factors in vasovagal syncope,” the authors write. “Analysis of the families suggests that complex inheritance (multiple genes ± environmental factors) is usual, with rarer families possibly segregating a major autosomal dominant gene.”

One author disclosed financial ties to the pharmaceutical industry and may accrue revenue from a pending patent.

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