The Athlete’s Heart
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
- •
Increased vagal tone
- •
Morphologic changes, including left ventricular (LV) enlargement, increases in LV wall thickness, and increases in LV mass
Pathologic vs. Physiologic Hypertrophy
- •
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
- •
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 and no limits on sports participation are required.
Sudden Cardiac Death
Epidemiology
- •
Sudden cardiac death (SCD) is the leading medical cause of death in young athletes.
- •
The actual incidence of SCD in athletes is difficult to estimate because of the lack of a mandatory national reporting system.
- •
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
- •
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
- •
The prevalence of cardiovascular disorders in young people that can potentially lead to SCD is approximately 1 in 300.
- •
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.
- •
SCD is the presenting symptom of underlying cardiovascular pathology in 50%–90% of athletes limiting the usefulness of a history-based screen.
- •
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 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
- •
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.
- •
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%
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