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Cardiac Disease in Athletes


The Athlete’s Heart

Definition

Intense regular physical exercise can induce physiologic and morphologic cardiac changes known as “athlete’s heart.” These adaptations are a normal response to repetitive exercise and training.

Physiologic Changes

  • Increased vagal tone

  • Morphologic changes, including left ventricular (LV) enlargement, increases in LV wall thickness, and LV mass

Pathologic vs. Physiologic Hypertrophy

  • Physiologic changes that occur in response to training can be difficult to differentiate from the pathologic processes that occur in hypertrophic cardiomyopathy (HCM) ( Table 35.1 ).

    Table 35.1
    Distinguishing Hcm From Athlete’s Heart
    HCM Athlete’s Heart
    Unusual pattern of LVH, may be heterogeneous Symmetric LVH or uniform distribution of hypertrophy
    Wall thickness >16 mm Wall thickness <12 mm
    LV cavity <45 mm (small) LV cavity >55 mm (not small)
    Left atrial enlargement No left atrial enlargement
    Abnormal LV filling Normal LV filling
    ECG abnormalities (see Chapter 34 : “ECG Interpretation in Athletes”) ECG with high voltage, but no Q-wave changes (see Chapter 34 : “ECG Interpretation in Athletes”)
    Thickness does not decrease with deconditioning LVH decreases with deconditioning
    Family history of HCM No family history of HCM
    Positive genetic testing for HCM Negative genetic testing for HCM
    ECG, Electrocardiogram; HCM, hypertrophic cardiomyopathy; LV, left ventricle; LVH, left ventricular hypertrophy.

  • Magnetic resonance imaging (MRI) can detect atypical patterns of hypertrophy and late gadolinium enhancement, which may be suggestive of HCM.

  • If the distinction between pathologic and physiologic hypertrophy cannot be established, a period of deconditioning should be considered.

Participation Recommendations

  • Athlete’s heart describes normal physiologic adaptations to regular intense exercise, and thus, no treatment or limits on sports participation are required.

Sudden Cardiac Death

Epidemiology

  • Sudden cardiac death (SCD) is the leading medical cause of death in young athletes.

  • Actual incidence of SCD in athletes is difficult to estimate because of the lack of a mandatory national reporting system.

  • High-quality studies suggest the incidence of SCD is around 1 in 50,000 athlete-years (AY) in college and 1 in 80,000 AY in high school athletes, with some higher-risk subgroups ( Table 35.2 ).

    Table 35.2
    Incidence of Sudden Cardiac Death And Arrest In Athletes
    Study Study Design and Population Case Identification Denominator Sports-Related SCD or All SCD? SCD or All SCA/D? Study Years Age Range; Number of Cases Annual Incidence
    Van Camp 1996 Retrospective cohort; high school and college athletes National Center for Catastrophic Sports Injury Research and media reports Data from NCAA, NFHS, NAIA, and NJCAA, added together with conversion factor (1.9 for high school and 1.2 for college) used to account for multisport athletes “based on discussions with representatives from the national organizations.” Sports-related SCD 1983–1993 13–24;
    N = 160     		College + High School:
    Overall 1:188,000
    Male 1:134,000
    Female 1:752,000
    High School:
    Overall 1:213,000
    Male 1:152,000
    Female 1:861,000
    College:
    Overall 1:94,000
    Male 1:69,000
    Female 1:356,000
    Maron 1998 Retrospective cohort; Minnesota high school athletes Catastrophic insurance claims Minnesota State High School League (Estimated using conversion factor of 2.3 to account for multisport athletes) Sports-related (school-sponsored only) SCD 1985–1997 16–17;
    N = 3     		High School:
    Overall 1:217,000
    Male 1:129,000
    Female 0
    Corrado 2003 Prospective cohort; athletes and nonathletes in the Veneto Region of Italy Mandatory reporting of sudden death Registered athletes in the Sports Medicine Database of the Veneto Region of Italy and the Italian Census Bureau All SCD 1979–1999 12–35;
    N = 51
    12–35;
    N = 208     		Athletes:
    Overall 1:47,000
    Male 1:41,000
    Female 1:93,000
    Nonathletes:
    Overall 1:143,000
    Drezner 2005 Retrospective survey; college athletes Survey of NCAA Division I institutions (244/326 responded) Reported number of athletes All SCD 2003 N = 5 College:
    Overall 1:67,000
    Corrado 2006 Prospective cohort; athletes and nonathletes in the Veneto Region of Italy Mandatory reporting to the Registry on Juvenile Sudden Death Registered athletes in the Sports Medicine Database of the Veneto Region of Italy and the Italian Census Bureau All SCD 1979–2004 12–35;
    N = 55
    12–35;
    N = 265     		Athletes:
    1:24,000 (prescreen)
    1:233,000 (postscreen)
    Nonathletes:
    1:127,000 (unscreened)
    Maron 2009 Retrospective cohort; amateur and competitive athletes US Registry for Sudden Death in Athletes An estimated 10.7 million participants per year ≤39 years of age in all organized amateur and competitive sports All SCA + SCD 1980–2006 8–39;
    N = 1046     		Athletes:
    1:164,000
    Drezner 2009 Cross-sectional survey; high school athletes Survey of 1710 high schools with AEDs Reported number of student athletes All cases occurring on campus SCA + SCD 2006–2007 14–17;
    N = 14     		High School:
    1:23,000 (SCA + SCD)
    1:64,000 (SCD)
    Holst 2010 Retrospective cohort; athletes and general population in Denmark Review of death certificates, Cause of Death Registry, and National Patient Registry in Denmark Interview data of people aged 16–35 years from the National Danish Health and Morbidity Study Sports-related SCD in athletes vs. all SCD in the general population SCD 2000–2006 12–35;
    N = 15
    12–35;
    N = 428     		Athletes:
    1:83,000
    General Population:
    1:27,000
    Marijon 2011 Prospective cohort; general population in France Data from emergency medical system General population statistics, data from the Minister of Health and Sport to estimate young competitive athlete population Sports-related SCA or SCD with moderate or vigorous exercise SCA + SCD 2005–2010 10–75;
    N = 820
    10–35;
    N = 50     		General Population:
    1:217,000
    Young Competitive Athlete:
    1:102,000
    Young Noncompetitive Athlete:
    1:455,000
    Steinvil 2011 Retrospective cohort; athletes in Israel Retrospective review of two Israeli newspapers Competitive athletes registered in the Israel Sport Authority in 2009; extrapolated this data for prior 24 years based on the growth of the Israeli population (age 10–40) from the Central Bureau of Statistics; allowed for a presumed doubling of the sporting population over 24 years All SCD 1985–2009 12–44;
    N = 24     		Athletes:
    1:38,000
    Harmon 2011 Retrospective cohort; college athletes Parent Heart Watch database, NCAA Resolutions list, catastrophic insurance claims Participation data from the NCAA All SCD 2004–2008 18–26;
    N = 37     		College:
    Overall 1:43,000
    Male 1:33,000
    Female 1:76,000
    Black 1:17,000
    White 1:58,000
    Male, black 1: 13,000
    Male, basketball 1: 7000
    Male, Div. I basketball 1:3000
    Maron 2013 Retrospective cohort; Minnesota high school athletes US Registry for Sudden Death in Athletes Minnesota State High School League statistics (Estimated using conversion factor of 2.3 to account for multisport athletes) All SCD 1986–2011 12–18;
    N = 13     		High School:
    Overall 1:150,000
    Male 1:83,000
    Female 0
    Roberts 2013 Retrospective cohort; Minnesota high school athletes Catastrophic insurance claims Minnesota State High School League statistics (Sum of unduplicated athletes 1993– 1994 through 2011– 2012 school years) Sports-related (school-sponsored only) SCD 1993–2012 12–19;
    N = 4     		High School:
    1:417,000 (1993–2012)
    1:909,000 (2003–2012)
    Female 0
    Maron 2014 Retrospective cohort; college athletes US Registry for Sudden Death in Athletes and NCAA resolutions list Participation data from the NCAA All SCD 2002–2011 17–26;
    N = 64     		College:
    Overall 1:63,000
    Male 1:56,000
    Female 1:333,000
    Black 1:26,000
    White 1:143,000
    Toresdahl 2014 Prospective observational; high school students and student-athletes 2149 high schools monitored for SCA events on school campus Reported number of students and student-athletes All cases occurring on school campus SCA + SCD 2009–2011 14–18;
    N = 44     		Student Athlete:
    Overall 1:88,000
    Male 1:58,000
    Female 1:323,000
    Student Nonathlete:
    Overall 1:326,000
    Male 1:286,000
    Female 1:357,000
    Drezner 2014 Retrospective cohort; Minnesota high school athletes Public media reports Minnesota State High School League statistics (Sum of unduplicated athletes 2003– 2004 through 2011– 2012 school years) All SCA + SCD 2003–2012 14–18;
    N = 13     		High School:
    Overall 1:71,000
    Female 0
    Male, basketball 1:21,000
    Harmon 2014 Retrospective cohort; high school athletes from 7 states in the United States Public media reports Participation data from the NFHS All SCA + SCD 2007–2013 14–18;
    N = 109     		High School:
    Overall 1:67,000
    Male 1:45,000
    Female 1:238,000
    Male, basketball 1:37,000
    Risgaard 2014 Retrospective cohort; competitive and noncompetitive athletes in Denmark Review of death certificates and the Danish National Patient Registry Competitive and noncompetitive athlete populations in Denmark estimated based on survey data from the Danish National Institute of Public Health Sports-related SCD in competitive vs. noncompetitive athletes SCD 2007–2009 12–35;
    N = 44     		Competitive Athlete:
    1:213,000
    Noncompetitive Athlete:
    1:233,000
    Harmon 2015 Retrospective cohort; college athletes Parent Heart Watch database, NCAA Resolutions list, catastrophic insurance claims Participation data from the NCAA All SCD 2003–2013 17–26;
    N = 79     		College:
    Overall 1:53,000
    Male 1:38,000
    Female 1:122,000
    Black 1:21,000
    White 1:68,000
    Football 1:36,000
    Male, soccer 1: 24,000
    Male, black 1: 16,000
    Male, basketball 1: 9000
    Male, black, basketball 1: 5300
    Male, Div. I basketball 1:5200
    Bohm 2016 Prospective cohort; sports-related SCD in all persons in Germany Voluntary reporting to German National Registry, web-based media search, regional institutes Physical activity estimated from the German Health Update study and extrapolated to population data from the German Federal Statistical Office Sports-related SCD SCD 2012–2014 10–79;
    N = 144     		Sports Participants:
    1:1,200,000
    Grani 2016 Retrospective; sports-related SCD in all persons in German-speaking Switzerland Forensic reports Physical activity estimated from survey on sports participation by the Swiss Federal Office of Sports Sports-related SCD SCD 1999–2010 10–39;
    N = 69     		Sports Participants:
    Competitive: 1:90,000
    Recreational: 1:192,000
    Maron 2016 Retrospective cohort Records of the Medical Examiner Data from the Minnesota Department of Education, National Center for Education Statistics, and the Minnesota State High School League for Hennepin County, Minnesota All SCD 2000–2014 14–23;
    N = 27     		Nonathlete:
    1:39,000
    Athlete:
    1:121,000
    Harmon 2016 Retrospective cohort, US high school athletes Media reports NFHS participation statistics All SCA/SCD 2007–2013 14–18;
    N = 104     		High School:
    Overall 1:67,000
    Male 1:45,00
    Female 1:237,000
    Male, basketball 1:37,000
    Chatard 2018 Prospective, Pacific Island athletes who were screened Prospectively followed Defined cohort of 1450 athletes SCD 2012–2015 10–40;
    N = 3     		Pacific Island Athletes:
    1:2416
    Malhotra 2018 Prospective Followed from time of screen to 2016 Defined cohort of 11,168 elite soccer athletes All SCD 1996–2016 15–17;
    N = 8     		Elite Male Soccer Athletes:
    1:14,794

  • Males and African Americans are at a higher risk, with men’s basketball appearing to be at a disproportionately higher risk: 1 in 9000 AY.

Presentation

  • The prevalence of cardiovascular disorders in young people that can lead to SCD is approximately 1 in 300.

  • Most individuals with cardiovascular disorders will not experience sudden cardiac arrest (SCA) or SCD; however, athletes may be at a higher risk because increased physical activity can trigger some arrhythmias.

  • SCD is the presenting symptom of underlying cardiovascular pathology in 50%–90% of athletes.

  • Warning symptoms of underlying cardiovascular disease include a history of exertional chest pain, exertional syncope or presyncope, dyspnea or fatigue disproportionate to the degree of exertion, and palpitations or irregular heartbeats. Athletes with any of these symptoms require a careful workup before returning to exercise.

  • A family history (FH) of sudden unexplained death or SCD before the age of 50 years or an FH of cardiac disorders known to cause SCD also warrant further diagnostic investigation before participation.

Etiology of SCD in Athletes

  • Older studies in US athletes suggested HCM as the leading cause of SCD in athletes; however, these data were subject to ascertainment bias. More recent studies in National Collegiate Athletic Association (NCAA) athletes and European athletes suggest that autopsy-negative sudden unexplained death (AN-SUD) is the most common cause of death, believed to be secondary to arrhythmias or electrical disease.

  • Studies in other countries and a recent meta-analysis suggest HCM may be less common as a cause of SCD ( Table 35.3 ).

    Table 35.3
    Studies of The Etiologies of Sudden Cardiac Death In Young People
    Study Years of Study Methods Autopsy Country “Sports-Related” or All Deaths Age Range Cases HCM Idiopathic LVH/Fibrosis Coronary Artery Anomalies ARVC DCM AN-SUD CAD Myocarditis Related Aortic Dissection LQTS WPW Other
    Corrado 1979–1999 Prospective, mandatory reporting, all deaths in Veneto region Standard procedure at referral center Italy All 12–35 46 2% 0% 13% 26% 2% 2% 22% 11% 2% 2% 0% 17%
    De Noronha 1996–2008 All cases SCD referred to CRY Standard procedure at referral center UK All 6–34 88 13% 32% 7% 10% 0% 30% 0% 3% 0% 0% 0% 6%
    Maron 1980–2006 Retrospective, registry, media reports Review of available autopsy, 359 had either pathologically normal heart or autopsy unavailable US All—includes SCA 8–39 1049 24% 5% 11% 3% 1% 34% 2% 4% 2% 2% 1% 10%
    Holst 2000–2006 Retrospective, death certificates Autopsy reports, hospital records Denmark Sports-related 12–35 14 0% 7% 7% 29% 0% 29% 14% 7% 0% 0% 0% 7%
    Suarez-Mier 1995–2010 All cases of SCD referred to National Institute of Forensic Sciences of Madrid Standard procedure at referral center Spain Sports-related 9–35 81 10% 9% 6% 15% 0% 23% 14% 5% 0% 0% 0% 19%
    Harmon 2003–2013 Retrospective, media reports, NCAA database Autopsy reports, ancillary reports US All 18–26 64 8% 17% 11% 5% 3% 25% 9% 9% 5% 2% 3% 3%
    Finochiaro 1994–2014 All cases SCD referred to CRY Standard procedure at referral center UK All 18–35 179 8% 14% 4% 14% 1% 44% 0% 2% 0% 0% 0% 13%
    Bohm 2012–2014 Retrospective Media reports, registry Germany Sports-related 10–34 29 7% 3% 10% 3% 3% 17% 21% 31% 0% 0% 0% 3%
    Harmon 2007–2013 Retrospective, media reports Autopsy reports US All 14–18 50 14% 28% 8% 2% 0% 18% 6% 14% 0% 0% 0% 12%
    Peterson 2014–2016 Media reports, reports to NCCSIR Autopsy reports US All 11–29 83 18% 16% 16% 5% 5% 10% 2% 4% 6% 4% 2% 13%
    Morentin 2010–2017 Retrospective Standard procedure at referral center Spain Sports-related 15–24 14 14% 21% 0% 36% 0% 0% 0% 21% 0% 0% 0% 7%
    Thiene 1980–2015 Prospective Standard procedure at referral center Italy All <40 75 5% 0% 16% 27% 0% 11% 23% 4% 0% 0% 0% 15%
    Total 1758 18% 9% 10% 7% 1% 30% 5% 5% 2% 2% 1% 11%

  • Specialized autopsy by a cardiovascular pathologist and molecular autopsy should clarify etiologies in the future.

Causes Of Sudden Cardiac Death

Structural

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