Definition

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

Physiologic Changes

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  Increased vagal tone

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

Pathologic vs. Physiologic Hypertrophy

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  The 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
  EKG abnormalities (see Chapter 30 )	EKG with high voltage, but no Q wave changes (see Chapter 30 )
  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

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

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

Participation Recommendations

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

Epidemiology

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

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

  
  
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  New research suggest the incidence of SCD is around 1 in 50,000 athlete-years (AY) in college athletes and 1 in 80,000 AY in high school athletes with some higher-risk populations ( Table 35.2 ).

  
  
  
  

  TABLE 35.2

  
  

  INCIDENCE OF SUDDEN CARDIAC DEATH AND ARREST IN ATHLETES

  
  

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Author	Year	Country	Method	Population	Incidence *	Number of Years	Age Range (Years)
  Boden	2013	US	Retrospective cohort	College/high school football	1 : 112,359 college 1: 312,500 high school
  Van Camp	1996	US	Retrospective cohort	College/high school athletes	1 : 300,000	10	17–24
  Maron	2009	US	Retrospective cohort	Athletes	1 : 163,934	27	8–39
  Steinville	2011	Israel	Retrospective cohort	Athletes	1st – 1 : 39,370 2 nd – 1 : 37,593	24	12–44
  Corrado	2003	Italy	Prospective cohort study	Athletes/young people	1 : 47,600 athlete 1 : 142,900 young people	20	12–35
  Holst	2010	Denmark	Retrospective cohort	Athletes/young people	1 : 82,645 athlete 1 : 26,595 general pop	7	12–35
  Drezner	2005	US	Retrospective cohort	College athletes	1 : 67,000	3.3
  Harmon	2011	US	Retrospective cohort	College athletes	1 : 43,000	5	18–26
  Harmon	2015	US	Retrospective cohort	College athletes	1 : 53,000	10	17–26
  Maron	2014	US	Retrospective cohort	College athletes	1 : 83,000 – confirmed 1 : 62,000 – presumed	10	17–26
  Drezner	2009	US	Cross-sectional survey	High school athletes	1 : 23,000 SCA + SCD 1 : 46,000 SCD
  Toresdahl	2014	US	Prospective observational	High school athletes	1 : 87,719 SCA + SCD	3	14–18
  Maron	2012	US	Retrospective cohort	High school athletes	1 : 150,000	26	12–18
  Roberts	2013	US	Retrospective cohort	High school athletes	1 : 416,666 last decade 1 : 917,000
  Maron	1998	US	Retrospective cohort	High school athletes	1 : 217,000 overall	11
  Marjion	2011	France	Prospective	Competitive athletes	1 : 102,00		10–35

   
  

  * Incidence numbers are in athlete-years.

  
  
  
  
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  Males and African Americans are at a higher risk, with men’s basketball appearing to be at a disproportionately higher risk: 1 in 9,000 AY.

Presentation

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

  
  
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  Most individuals with cardiovascular disorders will not go on to experience sudden cardiac arrest (SCA) or SCD; however, athletes may be at a higher risk because of their increased level of physical activity, which can be a trigger for arrhythmias.

  
  
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  SCD is the presenting symptom of underlying cardiovascular pathology in 50%–90% of athletes limiting the usefulness of a history-based screen.

  
  
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  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.

  
  
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  A family history of sudden unexplained death or SCD before the age of 50 years or a history of familial cardiac disorders known to cause SCD in young athletes also warrant further diagnostic investigation before participation.

Etiology of SCD in Athletes

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  Older studies in US athletes suggest HCM as the leading cause of SCD in athletes; however, more recent studies and studies in the US military suggest that a pathologically normal heart is the most common finding at autopsy.

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

  
  
  
  

  TABLE 35.3

  
  

  STUDIES OF THE ETIOLOGIES OF SUDDEN CARDIAC DEATH IN YOUNG PEOPLE

  
  

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Author	Year	Country	Exertional Death vs. All Deaths	Population	Age Range (Years)	Number of Deaths	HCM	Idiopathic LVH/ Possible HCM	Coronary Artery Abnormalities	ARVC	DCM	AN-SUD	CAD	Myocarditis Related	Aortic Dissection	Other
  Corrado	2003	Italy	all	Competitive athletes	12–35	55	2%	0%	13%	22%	0%	7%	20%	13%	2%	22%
  De Noronha	2009	UK	all	Athletes	1–35	89	12%	25%	8%	10%	0%	19%	8%	3%	0%	4%
  Maron	2009	US	all	Athletes	8–39	690	36%	8%	17%	4%	2%	–	3%	6%	3%	20%
  Holst	2010	Denmark	exertional	Competitive athletes	12–35	15	0%	7%	7%	27%	0%	27%	13%	7%	0%	13%
  Suarez-Mier	2011	Spain	exertional	Recreational athletes	9–35	81	10%	9%	6%	15%	%	23%	14%	5%	0%	19%
  Harmon	2014	US	all	Competitive athletes	18–26	36	3%	8%	14%	3%	8%	32%	5%	8%	8%	5%

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