Objectives Information about sudden cardiac arrest (SCA) in sports arises from registries, insurance claims and various reports. Analysing video footage of SCA during sports for scientific purposes has scarcely been done. The objective of this study was to examine videotaped SCA in athletes to better understand the mechanisms of SCA.
Methods Publicly available online video databases were searched for videos displaying SCA in athletes.
Results Thirty-five online videos (26 from professional and 9 from amateur sport; 34 male victims) were obtained. Twenty-one events resulted in survival and 14 in sudden cardiac death. Level of physical activity prior to SCA was assessable in 28 videos; 19 events occurred during low-intensity, 6 during moderate-intensity and 3 during high-intensity activity. SCA predominately occurred during low-intensity compared with both moderate-intensity and high-intensity activities (p<0.01). In 26/35 videos, it was possible to observe if resuscitation was provided. Resuscitation was carried out in 20 cases; cardiopulmonary resuscitation (CPR) alone (8 cases), CPR+defibrillation (10), cardiac thump (1) or shock from an implantable cardioverter defibrillator (1). Thirteen of the 20 cases with resuscitation received an intervention within 1 min after collapse. Survival was high when intervention occurred within 1 min (12/13) compared with those who received delayed (3/5) or no intervention (1/6). Associated signs of SCA such as agonal respirations and seizure-like movements were observed in 66% of the cases.
Conclusions SCA during sport most often occurred during low-intensity activity. Prompt intervention within 1 min demonstrated a high survival rate and should be the standard expectation for witnessed SCA in athletes.
- sudden cardiac death
- sudden cardiac arrest
- vagus nerve
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- sudden cardiac death
- sudden cardiac arrest
- vagus nerve
Sudden cardiac arrest (SCA) in sports is a tragic event and the leading cause of sudden death in competitive athletes.1 The available information about SCA in sports arises from prospective2–4 and retrospective1 5–7 registries, insurance claim,8 and media,7 9 voluntary7 and autopsy6 10–14 reports. Thus, estimates regarding risk, causes and timing of SCA during sports participation are available.
The actual mechanism that leads to SCA, though, is largely unknown. In athletes below 35 years, SCA is thought to be mostly arrhythmogenic and often on the background of an underlying structural or electrical pathological heart condition.11 15 Among athletes above 35 years, coronary atherosclerosis is the most common aetiology of SCA.6 11 15 16
Prompt management of SCA in athletes is critical to avert sudden death. While outcomes from SCA in athletes have been reported through registry data or case reports,3 17 events of SCA have not been visually analysed in a comprehensive study.
In our digital era, many events of SCA in sports have been videotaped which permits visual access to actual cases. Thus, the purpose of this study was to investigate the mechanisms and characteristics of SCA in athletes through a detailed video analysis. Specific questions examined were: timing of SCA related to the intensity of physical activity; the position, facial features, presence of seizure-like activity and agonal respirations of the victim; and the timing and specifics of the emergency intervention and how this influenced the outcome from SCA.
To obtain the videos, publicly available online databases including ‘Youtube.com’, ‘Google.com’, ‘Liveleak.com’, ‘ParentHeartWatch.com’ and ‘C-R-Y.org.uk’ were repeatedly searched from January through October 2017. Different search phrases related to cardiac arrest in sports such as ‘cardiac arrest sports’, ‘sudden cardiac arrest’, ‘cardiac arrest live footage’ and ‘collapse sports’ were used. Some videos were also found through news articles or were known to the authors. Some events were tracked in more than one database. Thirty-five online videos demonstrating SCA during organised sports or exercise were finally included from ‘Youtube.com’ (33 videos), ‘Google.com’ (1) and ‘Liveleak.com’ (1) (online supplementary table: links to online SCA videos). One video was removed from the internet during the project. Some other events were also censored.
Supplementary file 1
The included videos had to display the victim during one or more of these instances: preactivity leading up to the cardiac arrest, visualisation of the victim during the presumed cardiac arrest, or characteristics of the medical intervention. In all included events, further online research was conducted to confirm the findings and outcome of the SCA based on reports from medical personnel, coaches, players, family or the surviving victim. These reports were found as additional video interviews or text information added to the videotaped events, in news articles or Wikipedia.org (since most of the victims were professional athletes with personal Wikipedia articles).
Two videos of SCA were excluded because they did not display the victims during preactivity leading to SCA, throughout loss of consciousness or during the resuscitation.
In this observational study, no patients were involved at any point to obtain the study material.
The videos were analysed and categorised according to the following parameters: gender, race, age group, type of sport, professional or amateur sport, timing of collapse relative to competition, level of intensity just prior to collapse, position and facial features after collapse, presence of brief seizure-like activity or agonal respiration after collapse, type of intervention, timing for intervention (≤1 min=quick, >1 min=delayed, or no intervention) and survival as final outcome.
Physical intensity evaluation
The intensity of activity just prior to the SCA was divided into three different groups. Low intensity was defined as standing, walking or slow jogging. Moderate intensity was defined as faster jogging to running, however, not sprinting. High intensity was defined as sprinting, running, followed by jumping, doing rapid start and stop movements within the run of play or wrestling.
When the sportsman rapidly changed from one intensity phase to another, and then subsequently had an SCA, a cut-off time had to be set to define which intensity phase to categorise the SCA. After careful considerations of the videos, a 5 s cut-off time was chosen as this was the most feasible and demarcated best a distinct change in physical workload. For instance, if an athlete sprinted down the field, turned and starting walking and suffered SCA within less than 5 s of sprinting, this was still categorised as high intensity. If the athlete was standing, walking or slow jogging for more than 5 s after high-intensity activity, the SCA event was categorised as low intensity. In a particular group of events, a recurring observation was that SCA occurred during low-intensity activity following high-intensity activity. This subgroup of the low-intensity group was further defined to be in an ‘early recovery phase’ after high-intensity activity.
Associated signs of SCA
The victim’s body position, facial expressions, breathing patterns and movements were evaluated during the SCA. Known associated signs of SCA are seizures-like movements, agonal respiration (periodic abdominal or chest movements, abnormally deep breathing, and gasping and grunting), prone landing and eyes wide open/rolled backwards after assumed loss of consciousness.18–20 In three events, information about these associated signs was collected through statements from video interviews of two medical doctors and one school teacher actively involved in the resuscitation.
Fisher’s exact test was used to assess the effect of treatment on survival, while Χ2 test was used to assess event rates across pre-event activity levels.
The 35 videos depicted professional (n=26) and amateur (n=9) sports. The various sports involved are displayed in figure 1. Thirty-four of the victims were male. Twenty-nine of the collected events were of young athletes <35 years of age. In all videos (35/35) it was possible to obtain information regarding survival: 21/35 (60%) SCA events resulted in survival and 14/35 (40%) in sudden cardiac death (SCD). Characteristics of the SCA are summarised in figure 2.
Level of physical activity prior to SCA was possible to assess in 28 videos: 19 cases occurred during low-intensity, 6 during moderate-intensity and 3 during high-intensity activity. Thus, SCA predominantly occurred in low-intensity activity compared with both moderate-intensity and high-intensity activities (p<0.01). In 9/19 cases in which SCA occurred in a low-intensity phase, the SCA was preceded by a high-intensity phase more than 5 s before collapse (ie, early recovery phase).
In 26/35 videos, it was possible to observe if resuscitation was provided. Resuscitation was carried out in 20 cases: cardiopulmonary resuscitation (CPR) alone (8 cases), CPR+defibrillation (10), cardiac thump (1) or shock from an implantable cardioverter defibrillator (1). In the 20 resuscitated cases, 13 received the intervention within 1 min, 5 cases received the intervention after 1 min and 2 cases received intervention in which the timing could not be precisely determined. Six cases received no observable intervention at the site of the arrest. Among those who were quickly resuscitated within 1 min, 12/13 (92%) survived. This was significantly higher compared with the group with no observed resuscitation in which 1/6 (17%) survived (p<0.01). In the delayed resuscitation group 3/5 (60%) survived (p=0.35). Four victims recovered spontaneously after collapse initially attributed to SCA (figure 3). There were three incidences of presumed commotio cordis (victim struck in the chest leading to SCA) occurring in ice hockey, karate and soccer.
Signs associated with SCA were observed in 23 events (66%). In 10 events, more than one sign was observed. Collapsing forward into prone position without using arms for support was seen in 10 cases, eyes wide open or rolled backwards in 8 cases, seizure-like movements after collapse in 7 cases and agonal respirations present in 12 cases. When these associated signs of SCA were observed, the mortality rate was 9/23 (39%), similar to the mortality rate of 5/12 (42%) in the group without associated signs of SCA.
The associated signs of SCA were present in cases that did not receive resuscitation: 5/23 (22%) did not receive resuscitation and showed seizure-like movements (n=3), agonal respiration (3) or prone landing (1). Seizures and agonal respiration were each observed separately in two cases. In the group without associated signs of SCA, only 1/12 (8%) was not resuscitated. In the group with associated signs of SCA, 8/23 (35%) were quickly treated within 1 min vs 5/12 (42%) in the group with no associated signs of SCA.
This is the largest study to comprehensively review available videos of SCA in competitive athletes and among the first studies to analyse video-based material for sports-related SCA.21 Several findings should inform the mechanisms and management of SCA during sport. Sport-related SCA most often occurred in low-intensity activity. Victims resuscitated quickly (≤1 min) had the highest survival rate. A larger group of victims displayed signs associated with SCA that often went unrecognised and without early intervention for SCA.
Intensity level prior to SCA
A novel finding of this study was that SCA predominantly occurred during low-intensity activity, and not high-intensity activity as might be expected. It is not clear which arrhythmic mechanisms are causing SCA during these periods. However, there are theoretically several options related to the interplay of the sympathetic and parasympathetic nervous system. Exercise also affects release and regulation of intracellular and extracellular electrolytes in muscle cells, most importantly potassium, which could be influential in the mechanism of exercise-induced cardiac arrest.22
A common understanding is that SCA has a higher chance to occur during exercise compared with rest,23 as high adrenergic cardiac stimuli have the propensity to induce cardiac arrhythmias if a pathologic substrate is present. Increased sympathetic activation, elevated blood pressure and heart rate, and an altered metabolic state expected during prolonged high-intensity training may lower the arrhythmic threshold and may lead to SCA. Indeed, adrenergic cardiac stimuli have been proven to lower the threshold for cardiac tachyarrhythmias, while vagal stimuli are believed to be cardioprotective.24–26 In the current study, most cases of exercise-related SCA occurred during low-intensity activity. Additionally, nine cases of SCA occurred in a low-intensity phase preceded by a high-intensity phase. This might indicate that an athlete in such an early recovery phase after vigorous activity is at increased risk of SCA. Furthermore, it may be a partial explanation for the frequent SCA in a start/stop sport like soccer.14 The present data support this theory as eight of these nine cases occurred in swift ball games, soccer being predominant.
Within the first minute of recovery, especially after higher heart rates, vagal cardiac stimuli are increased to reduce the heart rate.27–29 Autonomic imbalance may occur which may prolong cardiac repolarisation and the refractory period, increasing the chance of a malignant arrhythmia.30
Presumably, parasympathetic stimuli to the heart may play a more significant role in the pathophysiological mechanism of SCA in athletes than previously believed. In a study of 357 athlete SCDs, 39% died during rest.31 These athletes were more likely to have normal hearts at postmortem examination compared with SCDs during exertion (54% vs 34%).31 The importance of vagal stimuli to SCA has also been raised in three large population-based studies of SCD in which a high proportion (13%–38%) of SCD occurred during sleep.13 32 33 By autopsy, SCD at night was also more often associated with structurally normal hearts.13 32 33
Furthermore, the present cases of SCD may occur in hearts with underlying ion channel abnormalities known sometimes to be triggered by increased vagal stimuli during exercise.28 33 34 Makimoto et al demonstrated that in 34/91 patients with Brugada syndrome, early recovery phase after treadmill exercise induced ST-segment augmentation in V1–V3, characteristic for Brugada syndrome.28 The typical ECG findings of Brugada syndrome were exacerbated, most likely, by increased vagal heart stimulus to slow down the heart rate. The same 34 patients showed a significantly higher risk of ventricular arrhythmias in the follow-up period of 75 months.28 Accordingly, undiagnosed ion channel abnormalities may be one explanation why SCA in athletes occurs in the early recovery phase. The frequent but varying degree of sudden unexplained death at autopsies (median 27%, range 6%–40%) in sports-related and general population studies on SCD1 6 10 13 32 33 may support this hypothesis.
At minimum, findings from the current study do not support the traditional premise that adrenergic stimuli are the direct and singular mechanism of SCA.
As expected, athletes who received quick resuscitation after SCA had a higher survival rate. The survival rate in the quick resuscitation group is comparable to other studies in which prompt resuscitation and early defibrillation were achieved in exercising athletes with SCA.3 Drezner et al reported 89% survival in high school student-athletes with a witnessed SCA during physical activity.3 Marijon et al 35 also demonstrated a nearly threefold higher survival rate in athletes compared with non-athletes. This was attributed to victims of sports-induced SCA being younger, with less underlying cardiovascular disease. The events were more often witnessed, allowing for CPR to be initiated faster. The rhythm was more often shockable.
Signs associated with SCA
The frequent observation of associated signs of SCA (seizure-like movements, agonal respiration, prone landing, eyes wide open/rolled backwards after assumed loss of consciousness) provides critical information to improve recognition of SCA in athletes. Drezner et al observed seizure-like movements in 50% of the student athletes with SCA.3 Panhuyzen-Goedkoop et al reported on six professional soccer players with SCA, and all six presented with eyes wide open and a fixed gaze.21 A Japanese study of mobile emergency response teams at marathons reported that 89% of runners with SCA demonstrated agonal respirations.36 The current study found agonal respirations in 34% of the cases, while seizure-like activity and abnormal gaze were seen in 20% and 23% of the cases, respectively.
Victims presenting with these signs of SCA may lead to delayed recognition of SCA and hence postpone resuscitation.37–39 In the current study, the group with associated signs of SCA was less likely to receive resuscitation and more often delayed, compared with the group without associated signs. This highlights that these associated signs can distract a responder and the collapse be misinterpreted for something other than SCA. More education to recognise SCA in an athlete, including the associated signs, is needed and may improve survival.
Evaluating the videos for the associated signs was challenging, however, as it required good quality imaging and direct view of the victims. In the 14 videos where the typical signs of SCA were not observed, it was often due to inadequate visualisation of the event, not necessarily lack of associated signs. The presented estimates, thus, should be taken as a lower estimate. Superior image quality, longer recording time and additional recording angles would allow enhanced characterisation of the associated signs of SCA in athletes.
Medical intervention at professional sports events
Most of the videos were taken at professional sports events. Based on visual observation of the medical intervention, in some events the medical personnel were not properly prepared for the SCA. Collapsed and unresponsive victims, in whom SCA was later confirmed, were sometimes placed in the lateral decubitus position, CPR was delayed several minutes and in some cases a defibrillator was not present at the stadium. It is feasible to improve survival rates with proper and quick initiation of CPR and use of an automated external defibrillator. With more education and practical training, the number of quickly resuscitated athletes can improve, reducing mortality and morbidity from SCA in sports.
Male athletes over-represented
In accordance with a body of literature on SCA in sports,1 6 7 23 40 41 there was a large over-representation of male victims. There are several reasons why male athletes are over-represented in video-recorded cases of SCA. Male sports often have a larger television audience, hence are more often recorded. Furthermore, male sex alone could be an independent risk factor for exercise-induced SCA.23 40 41
Spontaneous recovery after presumed SCA
Four videos showed spontaneous recovery after collapse from presumed SCA. Spontaneous recovery after cardiac arrest is considered rare. In these victims, the cause of collapse and brief loss of consciousness may have been from self-terminating ventricular tachycardia. Two of these victims died of SCD within a short time after the initial SCA; one victim the same day, the other victim 3 months after the initial event. These two examples illustrate the importance of extreme caution and a comprehensive cardiac evaluation in athletes with a non-traumatic collapse during exercise as an elevated risk of cardiac arrhythmia may still be present.
The identified cases are limited to video-filmed sports, creating an inherent bias towards events from the most popular and professional sports. Surely, many cases of SCA in athletes were missed. While the investigators used all available online resources to confirm the cases included were from SCA, an absolute guarantee that all victims entered SCA immediately after their collapse cannot be given. Other reports and interview statements from people involved with the resuscitation were used to confirm outcome of the events, and to acquire information regarding some parameters if the video recordings did not display sufficient information. Furthermore, the evaluation of physical intensity level and the possibility of vagal stimuli is hypothesised, but not confirmed, by physiologic measures. As the athletes were altering between different intensity levels, a cut-off period was necessary to define the intensity level that predominated just prior to SCA. Based on a thorough observation of all the videos and taken into account that a majority of the videos were short, a 5 s period was set as the cut-off to demarcate a change from one level of intensity to another. However, the level of autonomic nervous stimulation will certainly overlap between the intensity levels. Lastly, the degree of psychological stress the athletes were under, which also influences the autonomic balance, could not be assessed.
Video analysis was useful to evaluate exercise-induced SCA in sports. SCA occurred most often during low-intensity, not high-intensity activity, which may have implications on the autonomic mechanisms that lead to SCA in athletes. Prompt intervention had a positive effect on survival. Analysing the associated signs of SCA in collapsed athletes should inform training and management preparations to effectively respond to SCA during sports.
What are the findings?
Exercise-induced sudden cardiac arrest (SCA) most often occurred during low intensity, not high intensity of physical activity.
Agonal respiration, prone landing, seizure-like activity and abnormal eye gaze were observed in 66% of the events.
Associated signs of SCA were not associated with a faster response after SCA.
How might it impact on clinical practice in the future?
Further research is warranted to elucidate why SCA occurs more often during—or in the transition to low-intensity activity during sports.
Medical personnel and professional teams require additional training and preparations to adequately respond to SCA.
Better understanding of associated signs of SCA can be used to improve prompt recognition of SCA in athletes.
We thank statistician Joe Sexton, Diakonhjemmet Hospital, Department of Rheumatology, for valuable statistical help.
Contributors EES was responsible for the idea and concept of the research. DMS and EES was responsible for data collection and data analysis. Both authors were actively involved in the interpretation of the findings. DMS drafted the article, however both authors were actively involved with layout and writing. EES was mostly involved in critical review of the article, however both sides took part. Both DMS and EES approved the final version for publishing. The framework of the study was originated by EES. DMS and EES have worked together with inclusion of material, analysis and writing the paper.
Funding The authors have received a minor fund from Raagholtstiftelsen to finance this work.
Competing interests EES has previously received lecturer fees from Bayer, Sanofi and MSD.
Patient consent Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement This article is based on online videos of cardiac arrest in sports that are open to everyone. Information from analysing the videos is further backed up by online articles and video interviews of victims or bystanders which are also available online.