Barcelona, Spain, 31 August: A new definition of syncope – most commonly perceived as an episode of fainting – makes its diagnosis more precise and now dependent on a specific cause. New 2009 ESC Guidelines for the Diagnosis and Management of Syncope define syncope as "a transient loss of consciousness due to transient global cerebral hypoperfusion characterized by rapid onset, short duration and spontaneous complete recovery".(1)
The definition, says Professor Angel Moya from the University Hospital Vall d'Hebrón in Barcelona and Chair of the Guideline Task Force, now includes an aetiological requirement of reduced cerebral blood flow, which is new to the 2009 Guidelines. Indeed, he explains, a sudden cessation of cerebral blood flow for as short as six to eight seconds is sufficient to cause complete loss of consciousness. "Without this diagnostic addition," he says, "the definition of syncope becomes wide enough to include other disorders such as epileptic seizures and concussion - in fact, would be nothing more than 'loss of consciousness', irrespective of mechanism and duration."
The Guidelines note that syncope is also associated with a decrease in systolic blood pressure to 60 mmHg or lower, which in turn is determined by cardiac output and total vascular resistance; a fall in either can cause syncope, but a combination of both mechanisms is often present.
The new definition helps provide – for the first time – a clearer picture of who and how many are affected by this common condition, and what its longer-term health implications are. The Guidelines identify three common types of syncope, all with the same presentation (sudden loss of consciousness) but with different causes and different risk profiles.
Applying these definitions to everyday prevalence, Professor Richard Sutton of St Mary's Hospital, Imperial College, London, and Co-chair of the Guidelines Task Force, describes reflex syncope as "common" in the general population, with around 50% of us experiencing a VVS over a lifetime.(2) Prognosis is nearly always good.
Despite this broad prevalence, he says, many subjects with loss of consciousness are wrongly diagnosed and wrongly treated, with the potential for missing more serious conditions. However, with the right diagnosis, he adds, treatments for reflex syncope have improved in recent years: "We can provide the means to combat the symptoms of syncope. There is now evidence that physical treatments as well as 'tilt training' [extended periods of upright posture] are emerging as the new front-line treatment of reflex syncope. Two recent clinical trials have shown that isometric leg-crossing, hand grip and arm tensing exercises can induce a significant increase in blood pressure during the phase of impending syncope, which avoids or delays the loss of consciousness in most cases."
The Guidelines also put new emphasis on the increasing role of a diagnostic strategy based on prolonged monitoring, and not just on conventional laboratory testing. Implantable loop recorders, for example, which have a battery life of up to 36 months and a memory which stores ECG recordings, have already been shown to be cost-effective in the diagnosis of unexplained syncope, with a high correlation between symptoms and stored ECG data.
Both Professors Moya and Sutton thus believe there are three strong reasons for the new Guidelines: to prevent misdiagnosis (and inappropriate treatment, which is often expensive); to improve quality of life; and to recognise and reduce longer-term risk (especially in cardiac syncope). Because of the multifactorial nature of syncope as identified in the new diagnostic definitions, the Guidelines underline the important role of a dedicated multi-skilled "syncope unit", which would provide guideline-based assessment, risk stratification and treatment.
Driving
Among the quality of life questions addressed specifically by the Guidelines is whether those with syncope should drive. The new data "suggest that the risk of vehicle accident in patients with a history of syncope is not different from the general population of drivers without syncope". The Guidelines recommend for non-professional drivers:
For public safety, say the Guidelines, "the risk of syncope-mediated driving accidents (0.8% per year) appeared to be substantially less than in young (16 years) and in elderly drivers (high risk accident groups)".
Notes for editors
1. The Task Force for the Diagnosis and Management of Syncope of the European Society of Cardiology. Guidelines for the Diagnosis and Management of Syncope. Eur Heart J 2009; doi 10.1093/eurheartj/ehp298. The Guidelines will be presented simultaneously at the ESC Congress 2009 in Barcelona, 29 August – 2 September.
2. Most first faints occur between the ages of 10 and 30 years (around the age of 15 in 47% of females and 31% males), though 1% of toddlers in one study had VVS.