Abstract
Introduction: TheSudden Cardiac Death-Screening of Risk FactOrS survey included a
12-lead ECG plus a digital-based questionnaire and aimed to screen for
warning signs of diseases that may course with sudden cardiac death in
children and young-adults. We aimed to estimate the prevalence of
unexplained syncope (US) and characterize its high-risk features and
predictors in this cohort.
Methods and results: We determined the most probable etiology of
the transient loss of consciousness (TLOC) episodes based on clinical
criteria. US was an exclusion diagnosis and we analyzed its potential
clinical and ECG predictors. Among
11,878 individuals, with a mean age of 21±6 (range 6-40) years-old, the
cumulative incidence of TLOC was 26.5%, 76.2% corresponding to
females. Reflex syncope was present in 61.0%, orthostatic hypotension
in 7.9% and 12.6% of the
individuals had US. Unexplained syncope was independently associated
with age < 18 years-old (OR1.72; 95%CI
1.27-2.32,p<0.001), male gender (OR1.650; 95%CI
1.22-2.23,p=0.001), participation in competitive sports (OR1.64;95%CI
1.01-2.66,p=0.044), major syncope high-risk features (OR 2.61;95%CI
1.96-3.47,p<0.001), syncope after exertion (OR2.77;95%CI
1.80-4.27,p<0.001), fever context (OR9.58;95%CI
4.12-22.30,p<0.001), lower number of previous syncopal
episodes (OR0.36;95%CI 0.37-0.48,p<0.001) and history of
palpitations requiring medical care (OR1.98;95%CI 1.16-3.38,p=0.012).
We found no ECG predictors of US in this population.
Conclusions: The cumulative
incidence of TLOC in children and young-adults is high and remains
unexplained in an important proportion of individuals. We identified
eight clinical characteristics that may be useful for the risk
stratification of individuals evaluated in a non-acute setting.
Keywords: transient loss of
consciousness, unexplained syncope, predictors, children and
young-adults, athletes
Sudden cardiac death (SCD) in the
young population is relatively rare, with an estimated incidence of
0.46–3.7 events per 100 000 person-years among young-adults (1)(2) and
of approximately 7.8 per 100 000 persons during a 7-year period among
children.(3) Yet, it remains an important health problem that frequently
attracts media attention, as it frequently affects previously
healthy individuals and carries significant social and psychological
consequences to the relatives of the victims. The viability,
practicality and efficacy of screening programs is being put in question
by some, as nearly two-thirds of the events occur as the first clinical
manifestation of cardiac disease. (4)
The SCD – Screening of Risk FactOrS (SCD-SOS) survey aimed to
screen for clinical and electrocardiographic warning signs of potential
channelopathies and cardiomyopathies that may course with SCD in
children and young-adults. (5) A previous history of syncope is relevant
in this setting, although routine assessment of this symptom through
questionnaires has only been performed during pre-participation
screening of young athletes. (6)
The differential diagnosis of cardiac syncope with other causes of
transient loss of consciousness (TLOC) may be challenging, because TLOC
is prevalent among young-adults and it frequently has a benign
prognosis. While several individuals present with a typical history of
syncope with low-risk features that make the diagnosis of a reflex
mechanism or orthostatic hypotension (OH) more likely, some syncopal
events remain unexplained after initial evaluation. (7) On the other
side, the identification of high-risk features in individuals with
unexplained syncope (US) may suggest the presence of a serious
underlying cause and help to distinguish which patients warrant further
investigation and monitoring. Studies assessing high-risk features and
clinical predictors of US in the general children and young-adult
population are lacking. We aimed to estimate the prevalence of US and
characterize its high-risk features and predictors in the SCD-SOS
cohort.