Sports-related sudden cardiac deaths in the young population of Switzerland
Sports-related sudden cardiac deaths in the young population of Switzerland
Babken Asatryan 1 2
Cristina Vital 1 2
Christoph Kellerhals 1 2
Argelia Medeiros-Domingo 1 2
Christoph GraÈ ni 0 1
Lukas D. Trachsel 1 2
Christian M. Schmied 0 1
Ardan M. Saguner 0 1
Prisca Eser 1 2
David Herzig 1 2
Stephan Bolliger 1
Katarzyna Michaud 1
Matthias Wilhelm 1 2
0 University Heart Center , Zurich , Switzerland , 3 Institute of Forensic Medicine, University of Zurich , Zurich , Switzerland , 4 Unit of Forensic Medicine, University Center for Legal Medicine , Lausanne , Switzerland
1 Editor: Nanette H Bishopric, University of Miami School of Medicine , UNITED STATES
2 University Clinic for Cardiology, Inselspital, Bern University Hospital, University of Bern , Bern , Switzerland
³ These authors are shared second co-authors on this work
Over the 12-year study period, 349 SCD cases were recorded (mean age 30±7 years,
76.5% male); 297 cases were categorized as NONE, 31 as REC, and 21 as COMP.
Incidences of SCD per 100,000 person-years [mean (95% CI)] were the lowest in REC [0.43
(0.35±0.56)], followed by COMP [1.19 (0.89±1.60)] and NONE [2.46 (2.27±2.66)]. In all
three categories, coronary artery disease (CAD) with or without acute myocardial infarction
(MI) was the most common cause of SCD. Three professional athletes were identified in
COMP category which all had SCD due to acute MI. There were no time trends, neither in
overall, nor in cause-specific incidences of SCD.
Funding: The work was supported by an
unrestricted grant from the Swiss Heart
Foundation. The funders had no role in study
design, data collection and analysis, decision to
publish, or preparation of the manuscript.
In Switzerland, ECG screening was first recommended for national squad athletes in 1998.
Since 2001 it has become mandatory in selected high-risk professional sports. Its impact on the rates of sports-related sudden cardiac death (SCD) is unknown.
We aimed to study the incidence, causes and time trends of sports-related SCD in comparison to SCD unrelated to exercise in Switzerland.
The incidence of SCD in young individuals in Switzerland is low, both related and unrelated
to sports. In regions, like Switzerland, where CAD is the leading cause of SCD associated
with competitions, screening for cardiovascular risk factors in addition to the current PPS
recommendations might be indicated to improve detection of silent CAD and further
decrease the incidence of SCD.
Sudden cardiac death (SCD) in the young and apparently healthy individuals is a devastating
event with enormous impact on community health [
]. Reduction of cardiovascular mortality
is expected due to growing increase in awareness of risk factors over the past few decades, but
the SCD burden worldwide is still huge [
]. Despite numerous reports on the topic, our
knowledge about the precise incidence, demographics, causes and circumstances surrounding the
issue remain limited, as do regional differences [
SCD is a leading cause of death in competitive athletes [
]. The crucial role of regular
physical activities in reduction of mortality from cardiovascular disease is widely known and is
documented by several studies [
]. However, strenuous physical activities may provoke
lifethreatening arrhythmias in certain individuals at-risk [
]. Therefore, preventive measures are
required to protect susceptible individuals from exercise-related fatalities.
Aiming to reduce the rates of sports-related SCD, considerable importance has been given
to pre-participation screening (PPS) for early detection of silent cardiovascular pathologies
that predispose athletes to effort-induced life-threatening conditions. However, investigators
are still in search for more advanced screening methods that would detect the majority, if not
all individuals with silent, potentially fatal heart disease [
In Switzerland, PPS including an ECG has become mandatory for athletes in certain high
risk sports (e.g. ice hockey, soccer) since the end of 2001. The remaining athletic population is
screened on a voluntary basis and only 9% of non-elite athletes are screened [
]. The impact
of ECG-based PPS on rates of SCD related to exercise is unknown.
In Switzerland, unexpected deaths are reported to the district attorney, who then initiates
an inquiry to determine the manner of death (natural, accidental, homicidal or suicidal). The
preliminary forensic examination is an investigation of the scene, evaluation of the medical
history and thorough external examination of the corpse, mostly performed by a forensic
pathologist. The district attorney decides if further examination, such as an autopsy, is
necessary in a case-based approach . Based on a recent study in the Swiss canton of Vaud, the
autopsy rate in young SCD victims is 47.5% [
]. This autopsy rate seems valid for both
sports-related SCDs and SCDs unrelated to exercise, and applicable to all cantons .
We aimed to analyse the total, as well as sex-, and cause-specific incidences and time trends
of sports-related SCD in comparison to SCD unrelated to exercise in Switzerland.
We retrospectively reviewed all forensic autopsy reports of the German-speaking part of
Switzerland (population in the examined region is 5,617,963, which comprises nearly 70% of the
Swiss population) for sudden unexpected deaths in individuals aged 10±39 years, occurring
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between 1999 and 2010. Deaths were classified as SCD when they occurred within 24-hours of
symptom onset or beginning of physical activity, and either autopsy had identified a cardiac
pathology as the probable cause of death; or no obvious causes had been identified by the
postmortem examination and therefore a fatal arrhythmia was the likely cause of the event.
In Switzerland, forensic autopsy reports contain extensive information on autopsy results
and circumstances of death, which are stored in case-record databases of the Forensic Medical
Institutes. For efficient determination of manner and etiology of SCD, information on timing
of symptoms and activity preceding the event are obtained from bystanders, family members
and/or other witnesses, and are recorded in the forensic autopsy report.
Cases of SCD were classified into three categories based on whether or not sports were
performed within the 24-hours preceding the SCD: no sports (NONE), recreational sports (REC),
or competitive sports (COMP). Sports-related SCDs were included in COMP if they were
related to official athletic competitions, intended as an organized team or individual sport
event, placing high premium on athletic excellence and achievement [
]. All other
exerciserelated SCDs were categorized as REC. The timing of SCD was related to the onset of
symptoms (NONE) or the physical activity (REC, COM), classified into three groups: instantaneous,
within one hour, and within 24-hours [
Examination of the heart was performed by local forensic pathologists, and the
post-mortem diagnosis was based on macroscopic findings. When needed, microscopic and
toxicological examinations were performed to clarify the underlying pathology. The criterion for
hemodynamically relevant CAD was a lumen narrowing of 50% [
]. Data were recorded in
anonymized and standardized fashion in the electronic SWISS REGistry of Athletic Related
Death (www.swissregard.ch) .
The population data were derived from the Swiss Federal Statistical Office and a survey on
sports-participation in Switzerland from the Swiss Federal Office of Sports. The Swiss Federal
office of Statistics provided yearly population data of residents aged 10±39 years from the
German speaking cantons [
]. The survey on sports participation provided extensive data on
sporting activities, as well as volume and intensity of training . A core representative
sample of more than 10,000 15- to 75-year-old residents was first questioned by telephone,
followed by an online questionnaire on their sports participation. Children aged 10 to 14 years
were assessed with specially adapted questionnaires. The survey provided the ratios of people
engaged in recreational or competitive sports of the concerned age group. Based on this,
denominators for our three categories were formed as follows: all residents aged 10±39 years
(denominator for NONE category); subjects engaged in sports (denominator for REC); and
participants of competitions (denominator for COMP). Average yearly incidences were
calculated for the pre-screening (1999±2001), early screening (2002±2004), mid-screening (2005±
2007) and late screening (2008±2010) periods.
Data distribution was assessed by Shapiro-Wilk test. Continuous variables were compared
with the Student's t-test or Mann-Whitney U test, as appropriate. Categorical data were
analysed with Chi-squared test or FisherÂs exact test in case of low field numbers. P-values of all
outcomes were two-sided and a value less than 0.05 was considered significant.
Since our cohort included only autopsied SCD cases, we multiplied the recorded numbers
by a factor of 2.1 to adjust the numbers of SCDs for the average autopsy rate of 47.5% in
Switzerland in order to estimate real incidences [
The data was analysed with SPSS statistical package (SPSS Software for Windows, v. 17.0)
for descriptive statistics. Time trends were calculated by Poisson log-linear regression analysis,
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and average yearly incidences for pre-, early-, mid-, and late screening periods were calculated
per 100,000 person-years (statistical software R, R Core Team, 2015). For SCD rates, 95%
confidence intervals were calculated based on Poisson distribution with exact methods using the
software package epiR.
This study was evaluated by the Ethics Committee of the canton of Bern, Switzerland; for
analysis of health-related personal data no ethical approval was required. According to the Swiss
Law on Human Research, informed consent from next-of-kin for the retrospective analysis of
anonymised data was not necessary.
Characteristics of victims and the events
Over the observed period, the average annual population aged 10±39 years in the studied
region was 2,112,038 persons, with similar number of male (50.8%) and female inhabitants
]. Around 73% of men and women were engaged in sports, of whom 20% were involved in
competitions . The number of residents, their sports participation rate, age and sex
distribution remained stable over the observed period [
Overall, 82 women (23.5%) and 267 men (76.5%) aged 10±39 years suffered SCD in the
German-speaking part of Switzerland, accounting for an overall incidence of 2.89/100,000
person-years (mean age ± SD, 30±7 years; 76.5% male). Among all 349 individuals, 297 (85.1%)
deceased without an obvious connection to physical exercise (NONE), 31 cases (8.9%) were
related to recreational sports (REC) and 21 (6%) to competitive sports (COMP). Incidences of
SCD [mean (95% CI)] were the lowest in REC [0.43 (0.35±0.56)], followed by COMP [1.19
(0.89±1.60)] and the highest in NONE [2.46 (2.27±2.66)]. The incidence of SCD unrelated to
sports (NONE) was nearly 4 times higher compared to sports-related SCD (2.46 vs. 0.59).
We noted predominance of male victims in all three categories, and no significant
difference in mean age of subjects between groups (p = 0.732). The proportions of males in REC
(96.8%) and in COMP (85.7%) were greater than in NONE (73.7%) (p = 0.009). Out of 52
sports-related deaths, 48 occurred in men (92.3%). Three professional male athletes were
included in COMP, aged 26, 28 and 30 years.
The majority of SCDs occurred instantaneously or within 1 hour after the onset of initial
symptoms or sports. This tendency was the highest in REC (87.1%), and higher in COMP
(85.7%) than in NONE (53.9%). We observed the highest rate of witnessed cases in COMP
(85.7%), followed by REC (64.5%) and NONE (42.7%) (Table 1).
Distribution of underlying causes
CAD with or without acute myocardial infarction (MI) was the most common causative
pathology in all three groups; cause-specific incidences were 0.91 (0.80±1.03), 0.11 (0.07±0.18),
and 0.45 (0.28±0.73) for NONE, REC and COMP, respectively (Fig 1). Overall, premature
CAD accounted for death of 126 young individuals (89% male; 52% 35 years), comprising
36% of all SCDs.
Amongst all sports-related SCDs, 13.4% were due to acute MI, all cases being observed
below 35 years of age. In young male competitive athletes (age 35 years) acute MI was the
most common cause of SCD. Premature CAD with or without MI was responsible for 8 deaths
in COMP, which all occurred instantaneously or within 1-hour of exertion. All females who
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COMP, SCD related to competitions; NONE, SCD not related to physical activities; REC, SCD associated with physical activities other than competitions;
SCD, sudden cardiac death
died from acute MI (7 cases) were aged >25 years, and none of these deaths were related to
sports, while four young men aged 25 years died from acute MI.
In young women, aged 35years, cardiomyopathies were the leading pathological substrate
for SCD (40.7% of cases). In older females, CAD was more commonly observed (42%). Death
of three women was related to participation in competitive sports (COMP); they succumbed to
death due to WPW syndrome, myocarditis and valvular heart disease. The only female victim
in REC category had a morphologically normal heart on autopsy.
Among cardiomyopathies, hypertrophic cardiomyopathy (HCM) was the most frequent;
incidences in NONE, REC and COMP were 0.24 (0.19±0.31), 0.09 (0.05±0.15) and 0.11 (0.05±
0.29), respectively. In around half of SCD victims with underlying HCM, death was related to
recreational sports. There were 13 additional cases (12 in NONE and 1 in REC) where autopsy
revealed myocardial fibrosis and (borderline) left-ventricular hypertrophy, which could
possibly have been HCM; these were classified in a separate group (possible HCM/fibrosis) due to
unfulfilled histologic criteria (myocardial disarray) for post-mortem definite diagnosis of
Sports-related SCDs from other underlying cardiomyopathies were rare, only 13% of
sports-related deaths were due to dilated cardiomyopathy (DCM), arrhythmogenic right
ventricular cardiomyopathy (ARVC) or any other cardiomyopathy (Fig 2). ARVC was considered
the causative pathology in 2 cases, one in REC and one in COMP. All victims of ARVC and
coronary artery anomalies were aged 35 years or younger. Two of the three professional
athletes died during wrestling and one during ice hockey. No time trend for total or cause-specific
incidences of SCD was found in any of the groups (Fig 3 and Table 2).
Incidences and causes of death
Our study revealed an overall low incidence of SCD associated with competitive sports in the
young population of Switzerland. The identified incidence rates are comparable to the Italian
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Fig 1. Distribution of underlying causes of sudden cardiac death and their relation to exercise. ARVC,
arrhythmogenic right ventricular cardiomyopathy; CAD, coronary artery disease; CMP, cardiomyopathy; COMP, SCD
related to competitions; DCM, dilated cardiomyopathy; FMD, fibrous muscular dysplasia of coronary artery; HCM,
hypertrophic cardiomyopathy; MI, myocardial infarction; MVP, mitral valve prolapse; NONE, SCD not related to physical
activities; REC, SCD associated with physical activities other than competitions.
data in late screening period, and to a study conducted in the US [
]. We observed
predominance of male victims in all groups, consistent with other reports [16, 18±21].
Although mortality from cardiovascular disease, and particularly, CAD is very low in
], premature CAD was the most common cause of SCD in all categories. Similar
results were observed in the French speaking region of Switzerland [
]. All three professional
athletes identified amongst the victims in COMP included in the study succumbed to death
due to acute MI. It is worth mentioning that more than 50% of SCDs attributed to CAD in all
three categories occurred in the absence of acute MI. It is known that during intensive exercise
CAD can cause demand ischemia and cardiac arrest in the absence of acute MI [
this effect is not expected in non-athletic settings (NONE). It is possible that some of the SCDs
attributed to CAD in our NONE category were misclassified and these individuals had genetic
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Fig 2. Distribution of underlying causes of sports-related sudden cardiac death. Distribution of
underlying causes of sudden cardiac death (SCD) and their relation to recreational (REC) and competitive
sports (COMP) in age groups of 10±35 and 36±39 years. AMI, acute myocardial infarction; ARVC,
arrhythmogenic right ventricular cardiomyopathy; CAD, coronary artery disease; CMP, cardiomyopathies;
COMP, SCD related to competitions; DCM, dilated cardiomyopathy; HCM, hypertrophic cardiomyopathy;
REC, SCD associated with physical activities other than competitions; SCD, sudden cardiac death.
predisposition to life-threatening arrhythmias, however, these victims had an average age of 35
±3.2 years (37±2 years in REC (n = 4); and 35±3.5 years in COMP (n = 5)), therefore
channelopathies were less likely responsible for these deaths. It is also known that an unstable plaque
that is occluding only 30% to 50% is susceptible to transient coronary artery spasm as an
arrhythmia trigger [
Fig 3. Annual incidence rates of sudden cardiac death in the young population of the
Germanspeaking region of Switzerland. Young population included individuals aged 10 to 39 years. Sudden
cardiac deaths (SCDs) occurring between 1999 and 2010 were evaluated. Incidence rates are presented for
NONE, REC and COMP categories classified based on relation of the SCD to sports. COMP, SCD related to
competitions; NONE, SCD not related to physical activities; REC, SCD associated with physical activities
other than competitions.
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Total No. of
events in NONE
Total No. of
events in REC
Total No. of
events in COMP
0.60 (0.43±0.82) 0.814
0.33 (0.22±0.51) 0.949
0.43 (0.30±0.63) 0.762
0.20 (0.12±0.34) 0.792
0.10 (0.05±0.21) 0.916
0.13 (0.07±0.26) 0.976
0.17 (0.09±0.30) 0.693
0.20 (0.12±0.34) 0.908
a Includes cases of SCD with left ventricular hypertrophy and ®brosis but no myocardial disarray on histologic examination.
b Includes commotio cordis; congenital heart disease; coronary artery anomalies; ®brous dysplasia of the coronary arteries; other forms of
cardiomyopathies, systematic diseases; WPW syndrome and uncertain cases (4 cases).
c Time trends were calculated by Poisson log-linear regression analysis.
No case of myocarditis was recorded in REC. There were no deaths with pulmonary embolism, aortic dissection or morphological normal heart on autopsy
ARVC, arrhythmogenic right ventricular cardiomyopathy; CAD, coronary artery disease; CI, con®dence interval; CMP, cardiomyopathies; COMP, SCD
related to competitions; DCM, dilated cardiomyopathy; HCM, hypertrophic cardiomyopathy; MI, myocardial infarction; NONE, SCD not related to physical
activities; SCD associated with physical activities other than competitions; SCD, sudden cardiac death
The two previously mentioned seminal studies from Italy and the USA reported different
distributions of underlying causes of SCD in young athletes. Corrado and colleagues have
reported a predominant causative role of ARVC in SCD in athletes (25.4%) and a marked
decline in cause-specific incidence after implementation of nationwide mandatory ECG-based
]. In contrast, Maron et al. have found SCD in college athletes to be mainly due to
HCM (36%), followed by coronary artery anomalies (17%) [
]. Interestingly, in the same
study, HCM was observed 8 times more frequently than ARVC (251 vs. 30 cases). We observed
a high number of deaths caused by premature CAD and a low number of cases with ARVC
and HCM in our cohort, which is in line with reports from Denmark, Germany, Norway and
19, 20, 25, 26
]. The differences between the aforementioned studies support the theory
that regional differences in population characteristics play a central role in the epidemiology of
SCD, particularly in athletes . Our study further strengthens the evidence of regional
differences in underlying causes of SCD.
Trends of cardiovascular mortality and pre-participation screening
There is ample evidence of the effectiveness of ECG-based PPS in detecting certain inheritable
cardiac conditions. In the Veneto region of Italy, mandatory PPS including history, clinical
examination and resting 12-lead ECG substantially decreased the incidence of SCD in young
athletes from 4.19 to 0.87 cases per 100,000 person-years. The greatest decline was observed in
incidence rates of SCD due to ARVC±the most common cause of SCD in athletes in Veneto,
while the decline of SCD related to CAD or other conditions was not significant [
In our cohort, the average yearly incidence of COMP due to cardiomyopathies is similar to
the rates observed in Veneto over the late screening period (0.28 vs 0.15/100,000 athlete
]. We did not find a time trend in yearly incidence of SCD related to
cardiomyopathies in COMP after initiation of screening in athletes engaged in high-risk sports, as one
might expect. Annual absolute numbers of these cases were very low, which makes the
detection of a time trend more difficult.
There are at least three explanations to the overall low incidence of cardiomyopathies and
high incidence of CAD in our sample, that are particularly applicable to COMP. Firstly, since
the beginning of our data collection nearly coincides with the implementation of ECG-based
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PPS, the screening may have resulted in the exclusion of individuals with ECG-detectable
cardiomyopathies from competitions. Further, all military recruits in Switzerland undergo
ECGbased screening, and individuals with disorders detectable on routine ECG may have been
informed about potential risks related to the engagement in competitive sports. Alternatively,
it might be that the population examined in the present study has lower prevalence of
cardiomyopathies and higher rate of CAD.
It appears that PPS including ECG may prevent certain fatal cardiovascular events by
detecting underlying inherited/genetic conditions (as ARVC in Veneto), but additional
methods are needed to effectively identify candidates for SCD due to silent CAD. In these terms,
screening for cardiovascular risk factors such as hypertension, dyslipidemia, and family history
of premature CAD may be indicated to decrease mortality from CAD. The importance of
detection of CAD as a potential cause of SCD in athletes should be more emphasized in
regions where it is the leading cause of fatal cardiovascular events in athletes (e.g., Switzerland,
Norway, Germany, Denmark, Ireland) [
19, 20, 25, 26
Limitations of the study
This paper should be viewed in light of several limitations. The autopsy rate was low (47.5%)
due to autopsy being optional, which prevented us from generalizing our findings to all SCD
victims. In Switzerland, postmortem diagnosis is made by experienced forensic pathologists,
who are not necessarily specialized in cardiovascular pathology. Nevertheless, applying the
high diagnostic yield of histological examination and toxicological screening assures high
diagnostic accuracy. A study in college athletes in the US suggested that a multidisciplinary
expertpanel for comprehensive evaluation of pathological findings may improve the classification of
underlying causes, particularly of cardiomyopathies [
]. However, post-mortem diagnosis of
CAD±the most frequent underlying pathology in all categories in our study, is simple, unlike
the detection of non-obvious ARVC, HCM or myocarditis, which may require detailed
microscopic examination. Moreover, acute coronary occlusion due to thrombosis as the cause of
acute MI is a diagnosis not-to-miss and a certain cause of SCD [
It is possible that the NONE category included athletes who died in circumstances
unassociated with exercise [
], during routine daily activities or while asleep, when increased vagal
tone favors slower heart rate, such as in Brugada syndrome or Long QT syndrome type 3 [
]. However, this does not affect the results of this study, as we examined SCDs related to
competitions, rather than investigating SCDs in competitive athletes, therefore, the rates and
incidences observed should not be mistakenly assigned to athletes or non-athletes.
We have no explanation for the SCDs with morphological normal heart on autopsy. These
deaths could be related to inherited cardiac channelopathies but postmortem genetic testing is
not routinely perform in forensic pathology. The denominators for sports-participation were
based on survey results. However, our incidences are comparable to those of other studies
]. Given the higher proportion of witnessed cases in COMP and REC, compared to NONE,
the rates of sports-related SCD more reliably reflect the real incidences, while the rate in
NONE may be slightly underestimated due to lower witness (and autopsy) rate. Considering
also the adjustment for autopsy rate, the reported incidences for REC and COMP are at the
upper margin of the expected rates and are certainly not underestimated.
The incidence of SCD in the German-speaking part of Switzerland was low. CAD was the
predominant cause of SCD in sports-related and unrelated categories. Screening for
cardiovascular risk factors such as tobacco smoking, hypertension, dyslipidaemia, and family history of
10 / 13
premature CAD in addition to the current PPS recommendations might be indicated to
improve detection of silent CAD and further decrease the incidence of SCD.
S1 Dataset. Characteristics of sudden cardiac death victims.
S1 Appendix. Supporting information to the dataset.
Data curation: BA CV CK.
Formal analysis: MW BA CV CK CG PE DH.
Funding acquisition: MW.
Investigation: BA CV CK CG MW.
Methodology: MW CV CK BA.
Project administration: MW.
Resources: CV CK.
Software: CV CK.
Validation: CV CK BA MW.
Visualization: BA CV CK CG.
Writing ± original draft: BA.
Writing ± review & editing: BA CV CK AM-D LDT CG CMS AMS PE DH SB KM MW.
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