Life-Threatening Events During Endurance Sports - Core

JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY

VOL. 64, NO. 5, 2014

ª 2014 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION

ISSN 0735-1097/$36.00

PUBLISHED BY ELSEVIER INC.

http://dx.doi.org/10.1016/j.jacc.2014.05.025

Life-Threatening Events During Endurance Sports Is Heat Stroke More Prevalent Than Arrhythmic Death? Lior Yankelson, MD, PHD,* Ben Sadeh, MD,* Liron Gershovitz, MD,* Julieta Werthein, MD,y Karin Heller, MD,y Pinchas Halpern, MD,y Amir Halkin, MD,* Arnon Adler, MD,* Arie Steinvil, MD,* Sami Viskin, MD*

ABSTRACT BACKGROUND Two important causes of sudden death during endurance races are arrhythmic death and heat stroke. However, “arrhythmic death” has caught practically all the attention of the medical community whereas the importance of heat stroke is less appreciated. OBJECTIVES The study sought to determine what percentage of life-threatening events during endurance races are due to heat stroke or cardiac causes. METHODS This retrospective study examined all the long distance popular races that took place in Tel Aviv from March 2007 to November 2013. The number of athletes at risk was known. The number of athletes developing serious sport-related events and requiring hospitalization was known. Life-threatening events were those requiring mechanical ventilation and hospitalization in intensive care units. RESULTS Overall, 137,580 runners participated in long distance races during the study period. There were only 2 serious cardiac events (1 myocardial infarction and 1 hypotensive supraventricular tachyarrhythmia), neither of which were fatal or life threatening. In contrast, there were 21 serious cases of heat stroke, including 2 that were fatal and 12 that were life threatening. One of the heat stroke fatalities presented with cardiac arrest without previous warning. CONCLUSIONS In our cohort of athletes participating in endurance sports, for every serious cardiac adverse event, there were 10 serious events related to heat stroke. One of the heat stroke–related fatalities presented with unheralded cardiac arrest. Our results put in a different perspective the ongoing debate about the role of pre-participation electrocardiographic screening for the prevention of sudden death in athletes. (J Am Coll Cardiol 2014;64:463–9) © 2014 by the American College of Cardiology Foundation.

T

here is an increasing rise in the number of

races, involve an increased risk of sudden death (3).

recreational runners participating in long

Although the absolute risk for the participants is

distance races of 10 km or more, generally

low, ranging from 0.5 to 1.5 cases per 100,000

referred to as endurance races. For instance, approx-

athletes (3–7), such tragedies are particularly mean-

imately 500,000 runners crossed the finish line of a

ingful,

marathon race in the United States in 2011 alone, rep-

perceived to be healthy, dying as a result of partici-

resenting a 20-fold increase from the 25,000 finishers

pating in a recreational event.

because

in 1976 (1). Although regular physical activity is

they

involve

young

subjects,

SEE PAGE 470

generally considered healthy and is recommended by all major cardiovascular societies (2), long dis-

Two important causes of sudden death during

tance running, especially full and half marathon

endurance races are arrhythmic death and heat

From the *Department of Cardiology, Tel Aviv Sourasky Medical Center and Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel; and the yDepartment of Emergency Medicine, Tel Aviv Sourasky Medical Center and Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel. All authors have reported that they have no relationships relevant to the contents of this paper to disclose. Listen to this manuscript’s audio summary by JACC Editor-in-Chief Dr. Valentin Fuster. You can also listen to this issue’s audio summary by JACC Editor-in-Chief Dr. Valentin Fuster. Manuscript received January 11, 2014; revised manuscript received April 13, 2014, accepted May 12, 2014.

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JACC VOL. 64, NO. 5, 2014 AUGUST 5, 2014:463–9

Arrhythmias, Heat Stroke, and Endurance Sports

ABBREVIATIONS

stroke. Yet, arrhythmic death has caught the

but at night. The races offer several options for pro-

AND ACRONYMS

majority of attention from the medical com-

fessional and amateur participants, including 10 km,

munity. For example, a PubMed search (per-

half marathon (21.1 km), and full marathon (42.2 km)

formed

words

tracks. The 2 races are held within the perimeter of

[“arrhythmias”] AND [“athletes” OR “sports”] yields

downtown Tel Aviv, and the entire path of the races

>1,500 medical studies; in contrast, there are 104 F to 105 F (40.0 C to 40.5 C)

to our hospital. PARTICIPANTS. In these popular races, participants

associated with multiorgan dysfunction (8). Cerebral

range from highly trained athletes, mainly racing the

dysfunction, a sine qua non of this entity, ranges

marathon, to self-trained amateur athletes, mainly

from disorientation, confusion, loss of balance, irra-

participating in the popular 10 km and 21.1 km races.

tional behavior, apathy, aggressiveness, and delirium

Participants have to register in advance. The number

to sudden collapse with loss of consciousness.

of runners in each race was obtained from official

Importantly, the initial symptoms of heat stroke

online records, which track the athletes that cross the

often go unrecognized, so rapid deterioration culmi-

finish line (12).

nating in cardiac arrest (9) and ventricular fibrillation

The Israeli sports law states that pre-participation

(10) may occur. Moreover, in an athlete admitted af-

medical approval, including mandatory electrocar-

ter sudden collapse, the diagnosis of heat stroke will

diographic (ECG) screening, is required for partici-

be missed if—as often happens—the core body tem-

pants who are organized in teams or associations,

perature is not immediately measured (11). In such

but not for subjects attending public sporting events,

cases, a primary cardiac disorder may be suspected

such as these studied races. To participate in these

when arrhythmias predominate the clinical presen-

races, the runners only were required to submit

tation at the time of collapse.

a personal statement confirming a state of “good

During a 2011 Tel Aviv endurance race, heat stroke

health.” Nevertheless, to determine the percent of

by far outweighed cardiac conditions as the reason for

participants undergoing medical and/or ECG screen-

admission of participant athletes to our hospital

ing prior to the races, we performed a prospective

(a tertiary medical center, serving as the city hos-

evaluation using a questioner that was distributed

pital of Tel Aviv). In light of this, we conducted the

among participants of the 2013 race (see subsequent

present study to define the role of heat stroke and

sections).

cardiac arrhythmias as the cause of serious sudden adverse event among athletes participating in endurance races.

METHODS

MEDICAL EVENTS. Medical attention at all these

races included several levels: 1) the first level involves the national medical emergency service “Magen David Adom” (Israeli equivalent of the Red Cross) with ambulances, mobile intensive care units, and paramedics on motorcycles spread along the course of the

We performed a retrospective study of all the long

race; and 2) a first-line emergency station deployed by

distance races that took place in Tel Aviv between

the director of our Department of Emergency Medi-

March 2007 and November 2012 and prospectively

cine (P.H.) and fully trained emergency medicine

collected data for the 2013 races. The number of athletes participating in each 1 of the races was ob-

physicians from our hospital. This first line station is located nearby the finish line that is common to all the

tained from the official database of the race organi-

races. This station is fully equipped with means of

zations. The number of athletes experiencing serious

resuscitation,

sudden adverse events was determined from the

Initial medical attention is provided on the track by

number of race participants requiring emergency

either ambulance teams or scooters equipped with

medical care and hospitalization as a consequence of

basic and advanced life support capability. Following

medical event occurring during the race.

initial contact with an emergency service team,

RACES. Since 1997, public races have been conducted

patients are either discharged or transported for

in Tel Aviv twice a year. To avoid extreme weather

further evaluation and treatment. Patients in unstable

conditions, 1 daytime race (the Tel Aviv Race) is

condition, particularly those requiring resuscitation

conducted during early spring, whereas the other (the

maneuvers in the last part of the race, nearby the

Tel Aviv Night Run) is conducted during the summer

finish line, are transported to the first-line emergency

including

mechanical

respirators.

Yankelson et al.


station, where advanced medical care is available.


5.3 per 100,000). Both fatalities were due to heat

From there, patients are either discharged or further

stroke.

transported to our hospital. Importantly, participating

INCIDENCE OF SERIOUS EVENTS OF CARDIAC ORIGIN.

medical professionals are fully aware of the risks of

There were no fatalities caused by a primary

heat stroke and are instructed to actively search for

arrhythmia or by cardiac disease. Thus, the 95%

this diagnosis by checking rectal temperature imme-

confidence interval for the risk of cardiac death in

diately on arrival.

the Tel Aviv races was 0 to 2.2 per 100,000 partici-

We defined serious sports-related adverse events

pants. There were 2 hospitalizations for cardiac

as any medical problem occurring to an athlete

events, including a single case of non-fatal myocar-

participating in the race that resulted in either death

dial infarction and a single case of supraventricular

or hospitalization. One assigned investigator evalu-

tachyarrhythmia.

ated all these cases. A serious adverse event was

The myocardial infarction occurred in a 38-

further defined as life threatening (if cardiopulmo-

year-old man participating in the full marathon of

nary resuscitation or mechanical ventilation were

2011. He collapsed on the 20th km mark with chest

required and were followed by hospitalization in an

pain and dyspnea. Myocardial infarction was diag-

intensive care unit) or a fatal event (if it resulted

nosed and urgent cardiac catheterization revealed

in death). Confidence intervals of the mortality rate

single-vessel coronary disease with a complete oc-

were calculated with the Wilson score for binomial

clusion of the right coronary artery. Interestingly,

parameters (13).

this previously asymptomatic athlete had no known

PRE-PARTICIPATION SCREENING SURVEY. To assess

cardiovascular risk factors and had undergone pre-

the public compliance with Israeli Sports Law, which

participation screening that included resting ECG

mandates medical and ECG screening for those

and exercise stress tests repeatedly. One such exer-

participating in organized sports, we prospectively

cise test was performed only 3 weeks prior to the

conducted a questioner-based survey on the day of

race. The test was available for review: it was a

the 2013 Tel Aviv marathon race. Athletes partici-

maximal, symptom-limited exercise test and was

pating in the race were invited to take the survey

strictly normal.

sometime before crossing the starting line or after

The case with supraventricular arrhythmia was a

crossing the finish line. To encourage honest and

38-year-old man who nearly fainted while running

full disclosure, we conducted the survey in an

the 2012 Night Run. Hypotensive atrioventricular

anonymous fashion. The questions in the survey

nodal reentry tachycardia was documented at the

were based on the assessment recommended by the

time of symptoms and terminated onsite with aden-

American Heart Association (14). In addition, the

osine. The patient was hospitalized and eventually

survey collected information about the percent

underwent radiofrequency ablation therapy.

of race participants who had undergone screening

INCIDENCE OF SERIOUS EVENTS OF NONCARDIAC

with resting ECG and exercise stress testing. Of

ORIGIN. During the same time period, 21 cases of

note, the exact number and demographic features of

serious

the athletes who declined the survey were not

including 12 that were life threatening and 2 that were

recorded, so their comparison to survey participants

fatal.

exertional

heat

stroke

were

identified,

was not feasible. The Tel Aviv Sourasky Medical

The first fatality occurred during the 2011 Tel Aviv

Center ethics committee approved this study and

race. A 42-year-old man finished the 21.1-km-long

voided the need to obtain informed consent from

half marathon race and collapsed near the finish line.

the reported patients.

He immediately received basic and advanced life

RESULTS

temperature was documented in the first-line emer-

support at the first-line emergency station. His body gency-station as 41 C (105.8 F). Emergency therapy RACE-RELATED MORBIDITY AND MORTALITY. Overall,

included immediate and thorough cooling and me-

137,580 runners participated in all Tel Aviv races

chanical ventilation. He was hospitalized alive but

taking place from March 2007 to November 2013.

died of multiorgan failure 48 h later.

Serious adverse events (resulting in hospitaliza-

The second fatal event occurred during the Tel

tion or death) occurred in 23 athletes (Central

Aviv marathon of 2013. This race was scheduled for

Illustration). Two athletes died as a result of partic-

March 15, with races of 10 km, half marathon, and

ipation in a race, for a sport-related mortality rate of

full marathon planned. However, in view of an

nearly 1 per 69,000 (95% confidence interval: 0.4 to

official weather forecast predicting extremely high

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466

Yankelson et al.



N0. OF EVENTS

1

2

3

4

5

2007 Night Run 2007 Marathon 2008 Night Run 2008 Marathon 2009 Night Run 2009 Marathon 2010 Night Run 2010 Marathon 2011 Night Run 2011 Marathon 2012 Night Run 2012 Marathon 2013 Night Run 2013 Marathon

Serious cardiac event

Serious heat stroke

Life threatening

Fatal

C E N T R A L I L L U S T R A T I O N Serious, Life-Threatening and Fatal Events Due to Heat Stroke or Cardiac Disease in the Long Races Taking

Place in Tel Aviv (2007 to 2013)

Bars represent the number of serious adverse events (cardiac events in blue and heat–stroke–related events in salmon). None of the cardiac events were fatal or life threatening.

temperatures for the day of the race, the following

emergency station continued advance life support.

changes were made: 1) the marathon race was

The first documented arrhythmia was asystole. All

cancelled; and 2) the start time for the 10 km and 21.1

resuscitation maneuvers failed. The patient’s docu-

km races was advanced to early morning (scheduled

mented body temperature was >41 C (>105.8 F).

to start at 5:45 AM instead of 6:30 AM). Importantly, the

Twelve

additional

cases

of

near-fatal

heat

mean daily temperature on the week preceding the

stroke requiring mechanical ventilation followed by

race was 17.5 C (63.5 F) and the day before the race,

hospitalization in intensive care units were docu-

recorded temperatures were 16 C at 5:00

and 19 C

mented over the years (Central Illustration). In the

(66.2 F) at 11:00 AM. However, on the actual day of

most recent race, the 2013 10 km Tel Aviv Night Run,

the race, recorded temperatures were significantly

we identified 1 case of heat stroke presenting with

higher than during the previous week, with 24 C

syncope and tonic seizures. This was a 27-year-old

(75.2 F) recorded at 5:00

27 C (80.6 F) at 08:00

male, noncompetitive athlete who runs 10 km 3 times

and 35 C (95 F) around the time when the last

per week. Notably, he had mild diarrhea with low-

AM ,

AM ,

participant finished the race (11:00

AM ).

AM

On the 18 km

grade fever on the day before the race. He ran the

mark of the half marathon, a 29-year-old highly

race faster than usual and did not feel anything

trained male athlete had an unheralded cardiac ar-

wrong until he collapsed abruptly, shortly before the

rest. Basic cardiopulmonary resuscitation was star-

finish line. The rectal temperature recorded imme-

ted, and paramedics and a doctor from the first-line

diately in the ambulance was 40 C (104 F). He

Yankelson et al.



recuperated quickly in the emergency room and was

DISCUSSION

hospitalized for 2 days. exhaustion

Sudden death of athletes is an important topic that

requiring hospitalization but not in intensive care

We

identified

42

cases

of

heat

has drawn the attention not only of clinicians and

units. Of all cases with heat stroke or heat exhaus-

epidemiologists, but of the lay press as well. Some-

tion, 15 patients had abnormal ECG findings at the

what surprisingly however, professional and lay

time of hospitalization, including early repolarization

publications on sudden athlete deaths occurring

in 10 patients, ST-segment elevation depression in

during sporting activity have focused primarily on

3 patients, and T-wave inversion in 2 patients. The

arrhythmic events, whereas the mortality caused by

overall occurrence of serious sports-related adverse

heat stroke has received far less attention. This is

events is presented in the Central Illustration. On

evident not only from the number of medical publi-

average, for every serious cardiac event, there were

cations on sports-related mortality, with papers

10 serious and more than 5 life-threatening/fatal

related to arrhythmic death outnumbering those on

events due to heat stroke.

heat stroke by a factor of 5 (see previous text), but

COMPLIANCE WITH PRE-PARTICIPATION GUIDELINES.

also by the emphasis on pre-participation screening

A total of 513 runners participating in the 2013 race

of athletes for the prevention of arrhythmic death

agreed to participate in our survey (Table 1). Their

(15–17). It is within this context that our study is

mean age was 35 12 years and 74% of them were

important, showing that life-threatening events dur-

men. Of these athletes, 56% ran the 10 km race, and

ing endurance races taking place in warm climates

37% ran the 21.1 km race, (the 42.2 km marathon had

are more likely to be caused by heat stroke than by

been cancelled due to weather conditions). Only 35%

cardiac arrhythmias.

and 46% of athletes reported having undergone ECG

INTERPRETATION

screening during the previous 1 and 5 years previ-

collected data for 14 endurance races that took place

ously, respectively.

in Tel Aviv during the last 7 years, compiling data on

OF

OUR

MAIN

FINDINGS. We

almost 140,000 runners. Our mortality risk estimates are accurate, because the number of athletes experiT A B L E 1 Survey of Screening Guidelines: Results of Survey

Assessing Compliance With Pre-Participation Screening Guidelines Among Participants in the 2013 Tel Aviv Marathon

Mean age, yrs Male

ber of athletes participating in the races were known with fair accuracy, rather than estimated. The mor-

General Number of participants surveyed

encing fatal or life-threatening events and the num-

513 35.8 12 73.7

tality rate related to endurance race participation observed in the present was 1:69,000, which is within the range reported in others (3,4,18). However, all fatal and life-threatening events in our study were

Screening performed during the preceding 1 yr Physical examination

37.6

caused by heat stroke rather than by cardiac

Electrocardiogram

35.5

arrhythmias. Importantly, 1 fatality in a male athlete

Exercise stress test

34.5

resulting from cardiac arrest might have been

Echocardiography

20.1

Screening performed during the preceding 5 yrs

misclassified

as

a

primary

rhythm

disturbance

Physical examination

48.0

had the first responders not actively measured his

Electrocardiogram

46.4

rectal temperature as part of their emergency

Stress test

45.0

assessment.

Echocardiography

32.4

Symptoms reported Exertional chest pain

3.7

Syncope/pre-syncope

6.0

Exertional dyspnea

4.7

IMPORTANCE OF HEAT STROKE. Several lines of

evidence indicate that the hazards of heat stroke during sports are under-appreciated. First, the incidence of exertional heat stroke is as high as 1 to 2 cases per 1,000 participants in races held in hot and

Signs 10.5

humid environments (19,20). Heat stroke also strikes

2.9

in areas generally considered of mild climate. An

Sudden death before 50 yrs of age

4.1

half marathon race, held annually in Newcastle, Great

Heart disease before 50 yrs of age

10.1

Known murmur Known hypertension Family history

Cardiomyopathy/long QT/arrhythmia Values are mean SD or % unless otherwise indicated.

example is the Great North Run, the world’s largest

8.2

Britain. In 2009, 55 of 54,000 participants were diagnosed with exertional heat stroke (21) and in 2005, 4 athletes died with suspected heat stroke as the cause of death (22). Furthermore, in the 2007

467

468

Yankelson et al.



Chicago marathon, there were 300 reported cases

important implications. First, there are no clinical

of heat-related injuries among 35,000 runners,

studies of potential strategies to prevent heat stroke

including 1 fatality (23). Second, the risk of heat

during endurance sports. Conceptually, a number

stroke is not limited to endurance races. According to

of interventions could be used to minimize risk.

a Centers for Disease Control and Prevention survey

Because the likelihood of heat stroke is enhanced by

on sport-related injuries among high school athletes

lack of acclimatization, a period of 10 to 14 days

(24), heat stroke was a leading cause of death during

should be allowed for proper adjustment to warm

the time period of 2005 to 2009. In a separate survey

climate (29). Recognizing the key role of acclimati-

by the National Center for Catastrophic Injury

zation is important for individual participants living

Research, heat stroke was an important cause of

in cooler areas, who should arrive at the location

death among high school and college football players

of the race earlier. Event planners also should

(25), who train and compete wearing heavy protec-

acknowledge the need for acclimatization. Ironically,

tive equipment. Even experienced runners, who have

the customary practice of scheduling endurance races

completed several marathons uneventfully, are not

during the spring, rather than the summer to avoid

immune (26).

the hottest weather, may actually increase the risk

IS HEAT STROKE UNDER-REPORTED AS CAUSE OF

for heat stroke by reducing the time available for

SPORTS-RELATED CARDIAC ARREST. The largest

acclimatization. Second, pre-existing fever impairs

series reporting on cardiac arrest during endurance

human ability to dissipate the additional heat stress

sports is a retrospective analysis of >10 million par-

imposed by exercise. It is thus not surprising that

ticipants in long distance races taking place in the

heat stroke survivors often report a recent minor

United States during the last decade (3). In this large

illness (30). Thus, candidates should be warned

series, only 3% of fatal cardiac arrests were due to

against participation in endurance sports if they are

heat stroke. However, the fact that none of the non-

presently ill or recuperating from a recent febrile

fatal cardiac arrests were ascribed to this entity

illness. Third, experienced runners, as well as onsite

raises the possibility that heat stroke remained

witnesses and health care providers, may be totally

underdiagnosed in this retrospective study (9). The

unaware of a developing heat stroke. Unfortunately,

diagnosis of heat stroke depends on accurate mea-

delays in diagnosis will inevitably postpone the

surement of body temperature. However, any tem-

initiation of cooling therapy. A potential solution to

perature measurement other than rectal or by

this problem may be the use of ingestible thermistors

invasive techniques is likely to be spuriously low;

that can reliably record body core temperature during

this is true for skin, oral, and aural measurements

physical activity (31). Technological refinements

(27). Yet, social-cultural conceptions and logistic is-

allowing for cheaper telemetry devices could even-

sues may prevent the implementation of immediate

tually prove to be useful in monitoring large numbers

rectal temperature assessment following collapse in a

of runners. Finally, there is an ongoing debate con-

race, especially in urban areas. Unheralded collapse

cerning the role of ECG pre-participation screening

(9) with documented ventricular fibrillation (10) may

for the prevention of sudden death among athletes

be the mode of presentation of heat stroke. In this

(32,33), and our findings place that debate in a

setting, the correct diagnosis will be missed if, as

different perspective.

often happens (11), the rectal temperature is not

STUDY LIMITATIONS. It could be argued that heat

measured promptly. In the largest analysis of adverse

strokes outnumbered arrhythmic events in our study

events during long races (3), a considerable percent

only because pre-participation screening of athletes

of cardiac arrest victims had inconclusive diagnoses.

with resting ECG and exercise stress testing elimi-

Given the frequent failure to measure core body

nated the risk of arrhythmic events. However, most

temperature, it is plausible that some of these events

race participants were not members of sports orga-

were erroneously attributed to cardiac conditions on

nizations and were not legally obliged to undergo

the basis of incidental pathological findings, whereas

any pre-participation screening. In fact, the only

heat stroke was the real etiology. For survivors of the

screening most of these runners underwent was

event, the ECG abnormalities commonly caused by

a declaration of “good health” during registration.

heat stroke (28) may lead the treating physician away

Specifically, only one-third of race participants

from the correct diagnosis.

answering our survey reported undergoing ECG heat

screening during the year preceding the race. More-

stroke is likely to be a more common cause of sport-

over, we have evidence indicating that ECG screening

related

has had no impact on athletes’ mortality in Israel (34).

CLINICAL

IMPLICATIONS. Recognizing

death

than

commonly

that

appreciated

has

Yankelson et al.



CONCLUSIONS

PERSPECTIVES

In this study involving almost 140,000 athletes participating in endurance sports, fatal or lifethreatening events during endurance races were caused exclusively by heat stroke. Serious cardiac events were extremely rare and outnumbered by heat stroke events by a factor of 10.

COMPETENCY IN MEDICAL KNOWLEDGE: The optimum strategy for detecting cardiovascular disease and preventing sudden death in recreational runners is controversial. COMPETENCY IN PATIENT CARE: Prompt diagnosis of heat stroke and rapid implementation of cooling can avoid cata-

A C K N O W L E D G E M E N T The authors thank Alex

Pine, PhD, for his advice with statistics.

strophic injury and adverse cardiovascular outcomes in patients who collapse while running. TRANSLATIONAL OUTLOOK: Additional studies are needed to

REPRINT REQUESTS AND CORRESPONDENCE: Dr.

validate technologies for continuous cardiovascular monitoring to

Sami Viskin, Department of Cardiology, Tel Aviv

prevent heat stroke and other causes of cardiovascular collapse in

Medical Center, Weizman 6, Tel Aviv 64239, Israel.

runners.

E-mail: [email protected].

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