Prevalence of family history in vasovagal syncope and haemodynamic response to head up tilt in first degree relatives: preliminary data for the Newcastle cohort.

UNLABELLED: Vasovagal syncope is an exaggerated form of the common faint affecting all age groups. Aetiology is unknown but the tendency for the disease to run in families has previously been noted. AIM: To determine the true prevalence of family history in subjects with a definitive diagnosis of vasovagal syncope made by positive head up tilt with symptom reproduction. To determine the strength of the genetic effect in vasovagal syncope by calculation of sibling (lambdas) and offspring (lambdao) relative risk. Haemodynamic responses to head up tilt were also examined in a sample of first-degree relatives of those with vasovagal syncope.
RESULTS: All subjects identified from the Cardiovascular Investigation Unit database with a definitive diagnosis of vasovagal syncope (n = 603) between 1993-2001 were asked to complete a questionnaire. 19% had positive family history for blackouts or faints. From these pedigrees and using a crude estimate of population prevalence, sibling and offspring relative risk was calculated: lambdas = 1080, lambdao = 1356. Eleven first-degree relatives from 6 families attended for head up tilt testing with glyceryl trinitrate (GTN) provocation (4 unaffected, 7 affected). All subjects had symptoms in response to tilt in association with a range of haemodynamic responses.
CONCLUSIONS: Vasovagal syncope has a strong genetic component. Elucidating underlying genetic mechanisms may lead to more effective, specific treatments.