Sudden cardiac death of athletes

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Defibrillator training kit Medtronic aed training kit.jpg
Defibrillator training kit

It remains a difficult medical challenge to prevent the sudden cardiac death of athletes, typically defined as natural, unexpected death from cardiac arrest within one hour of the onset of collapse symptoms, excluding additional time on mechanical life support. [1] (Wider definitions of sudden death are also in use, but not usually applied to the athletic situation.) Most causes relate to congenital or acquired cardiovascular disease with no symptoms noted before the fatal event. The prevalence of any single, associated condition is low, probably less than 0.3% of the population in the athletes' age group,[ citation needed ] and the sensitivity and specificity of common screening tests leave much to be desired. The single most important predictor is fainting or near-fainting during exercise, which should require detailed explanation and investigation. [2] The victims include many well-known names, especially in professional association football, and close relatives are often at risk for similar cardiac problems.

Contents

Causes

The sudden cardiac deaths of 387 young American athletes (under age 35) were analyzed in a 2003 medical review: [3]

CauseIncidence
Hypertrophic cardiomyopathy 26%Genetically determined
Commotio cordis 20%Structurally normal heart, disrupted electrically by a blow to the chest
Coronary artery anomalies 14%Exact mechanisms unknown; some association with other congenital CVS abnormalities
Left ventricular hypertrophy of undetermined origin7%Probable variant of hypertrophic cardiomyopathy
Myocarditis 5%Acute inflammation
Ruptured aortic aneurysm (Marfan syndrome)3%Genetically determined; also associated with unusual height
Arrhythmogenic right ventricular cardiomyopathy 3%Genetically determined
Tunneled coronary artery 3%Congenital abnormality
Aortic valve stenosis 3%Multiple causes
Atherosclerotic coronary artery disease 3%Mainly acquired; dominant cause in older adults
Other diagnosis13%

While most causes of sudden cardiac death relate to congenital or acquired cardiovascular disease, an exception is commotio cordis, in which the heart is structurally normal but a potentially fatal loss of rhythm occurs because of the accident of timing of a blow to the chest. Its fatality rate is about 65% even with prompt CPR and defibrillation, and more than 80% without. [4] [5]

Age 35 serves as an approximate borderline for the likely cause of sudden cardiac death. Before age 35, congenital abnormalities of the heart and blood vessels predominate. These are usually asymptomatic prior to the fatal event, although not invariably so. [6] Congenital cardiovascular deaths are reported to occur disproportionately in African-American athletes. [7]

After age 35, acquired coronary artery disease predominates (80%), [6] and this is true regardless of the athlete's former level of fitness.[ citation needed ]

Various performance-enhancing drugs can increase cardiac risk, though evidence has been inconclusive about their involvement in sudden cardiac deaths. [8]

Genetics

Cardiomyopathies

Arrhythmogenic right ventricular dysplasia, showing fatty infiltration of right and left ventricle, and poor contraction of right ventricle Cardiac magnetic resonance Arrhythmogenic right ventricular dysplasia.gif
Arrhythmogenic right ventricular dysplasia, showing fatty infiltration of right and left ventricle, and poor contraction of right ventricle

Cardiomyopathies are generally inherited as autosomal dominants, although recessive forms have been described, and dilated cardiomyopathy can also be inherited in an X-linked pattern. Consequently, in addition to tragedy involving an athlete who succumbs, there are medical implications for close relatives. Among family members of index cases, more than 300 causative mutations have been identified. However, not all mutations have the same potential for severe outcomes, and there is not yet a clear understanding of how these mutations (which affect the same myosin protein molecule) can lead to the dramatically different clinical characteristics and outcomes associated with hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). [9]

Since HCM, as an example, is typically an autosomal dominant trait, each child of an HCM parent has a 50% chance of inheriting the mutation. In individuals without a family history, the most common cause of the disease is a "de novo" mutation of the gene that produces the β-myosin heavy chain.[ citation needed ]

Channelopathies

Sudden cardiac death can usually be attributed to cardiovascular disease or commotio cordis, but about 20% of cases show no obvious cause and remain undiagnosed after autopsy. Interest in these "autopsy-negative" deaths has centered around the "ion channelopathies". These electrolyte channels are pores regulating the movement of sodium, potassium and calcium ions into cardiac cells, collectively responsible for creating and controlling the electrical signals that govern the heart's rhythm. Abnormalities in this system occur in relatively rare genetic diseases such as Long QT syndrome, Brugada syndrome, and Catecholaminergic polymorphic ventricular tachycardia, all associated with sudden death. Consequently, autopsy-negative sudden cardiac deaths (no physical abnormalities identified) may comprise a larger part of the channelopathies than previously anticipated. [10] [11]

Heritable connective tissue diseases

Myxomatous degeneration of the aortic valve, common in Marfan syndrome Myxomatous aortic valve.jpg
Myxomatous degeneration of the aortic valve, common in Marfan syndrome

Heritable connective tissue diseases are rare, each disorder estimated at one to ten per 100,000, of which Marfan syndrome is the most common. It is carried by the FBN1 gene on chromosome 15, which encodes the connective protein fibrillin-1, [12] [13] inherited as a dominant trait. This protein is essential for synthesis and maintenance of elastic fibers. Since these fibers are particularly abundant in the aorta, ligaments, and the ciliary zonules of the eye, these areas are among the worst affected. Everyone has a pair of FBN1 genes and, because transmission is dominant, those who have inherited one affected FBN1 gene from either parent will have Marfan syndrome. Although it is most frequently inherited as an autosomal dominant, there is no family history in 25% of cases. [14]

Recruiting practices aimed at attracting athletes who are unusually tall or who have an unusually wide arm span (characteristics of Marfan syndrome) can increase the prevalence of the syndrome within sports such as basketball and volleyball. [15]

DNA testing

After a disease-causing mutation has been identified in an index case (which is not always accomplished conclusively), the main task is genetic identification of carriers within a pedigree, a sequential process known as "cascade testing". Family members with the same mutation may show different severities of disease, a phenomenon known as "variable penetrance". As a result, some may remain asymptomatic, with little lifelong evidence of disease. Nevertheless, their children remain at risk of inheriting the disorder and potentially being more severely affected. [16]

Screening

Echocardiogram showing left ventricle PLAX Mmode.jpg
Echocardiogram showing left ventricle

Screening athletes for cardiac disease can be problematic because of low prevalence and inconclusive performance of various tests that have been used. Nevertheless, sudden death among seemingly healthy individuals attracts much public and legislator attention because of its visible and tragic nature. [17]

As an example, the Texas Legislature appropriated US$1 million for a pilot study of statewide athlete screening in 2007. The study employed a combination of questionnaire, examination and electrocardiography for 2,506 student athletes, followed by echocardiography for 2,051 of them, including any students with abnormal findings from the first three steps. The questionnaire alone flagged 35% of the students as potentially at risk, but there were many false positive results, with actual disease being confirmed in less than 2%. Further, a substantial number of screen-positive students declined repeated recommendations for follow-up evaluation. (Individuals who are conclusively diagnosed with cardiac disease are usually told to avoid competitive sports.) It should be stressed that this was a single pilot program, but it was indicative of the problems associated with large-scale screening, and consistent with experience in other locations with low prevalence of sudden death in athletes. [18]

Incidence

Sudden cardiac death occurs in approximately one per 200,000 young athletes per year, usually triggered during competition or practice. [6] The victim is usually male and associated with association football, basketball, ice hockey, or American football, reflecting the large number of athletes participating in these sustained and strenuous sports. [3] For a normally healthy age group, the risk appears to be particularly magnified in competitive basketball, with sudden cardiac death rates as high as one per 3,000 annually for male basketball players in NCAA Division I. [19] This is still far below the rate for the general population, estimated as one per 1,300–1,600 and dominated by the elderly. [20] However, a population as large as the United States will experience the sudden cardiac death of a competitive athlete at the average rate of one every three days, often with significant local media coverage heightening public attention. [17]

In the United States approximately 8 to 10 deaths per year can be attributed to sudden cardiac death in NCAA with overall rate of 1 per 43,000. [21] [22]

Notable cases

This is a dynamic list and may never be able to satisfy particular standards for completeness. You can help by adding missing items with reliable sources.

These athletes, with notable careers, experienced sudden cardiac death by age 40.

See also

Related Research Articles

<span class="mw-page-title-main">Cardiology</span> Branch of medicine dealing with the heart

Cardiology is the study of the heart. Cardiology is a branch of medicine that deals with disorders of the heart and the cardiovascular system. The field includes medical diagnosis and treatment of congenital heart defects, coronary artery disease, heart failure, valvular heart disease, and electrophysiology. Physicians who specialize in this field of medicine are called cardiologists, a specialty of internal medicine. Pediatric cardiologists are pediatricians who specialize in cardiology. Physicians who specialize in cardiac surgery are called cardiothoracic surgeons or cardiac surgeons, a specialty of general surgery.

<span class="mw-page-title-main">Marfan syndrome</span> Genetic disorder involving connective tissue

Marfan syndrome (MFS) is a multi-systemic genetic disorder that affects the connective tissue. Those with the condition tend to be tall and thin, with long arms, legs, fingers, and toes. They also typically have exceptionally flexible joints and abnormally curved spines. The most serious complications involve the heart and aorta, with an increased risk of mitral valve prolapse and aortic aneurysm. The lungs, eyes, bones, and the covering of the spinal cord are also commonly affected. The severity of the symptoms is variable.

<span class="mw-page-title-main">Cardiomyopathy</span> Disease of the heart muscle

Cardiomyopathy is a group of primary diseases of the heart muscle. Early on there may be few or no symptoms. As the disease worsens, shortness of breath, feeling tired, and swelling of the legs may occur, due to the onset of heart failure. An irregular heart beat and fainting may occur. Those affected are at an increased risk of sudden cardiac death.

<span class="mw-page-title-main">Cardiac arrest</span> Sudden failure of heart beat

Cardiac arrest, also known as sudden cardiac arrest, is when the heart suddenly and unexpectedly stops beating. As a result, blood cannot properly circulate around the body and there is diminished blood flow to the brain and other organs. When the brain does not receive enough blood, this can cause a person to lose consciousness. Coma and persistent vegetative state may result from cardiac arrest. Cardiac arrest is also identified by a lack of central pulses and abnormal or absent breathing.

<span class="mw-page-title-main">Brugada syndrome</span> Heart conduction disease

Brugada syndrome (BrS) is a genetic disorder in which the electrical activity of the heart is abnormal due to channelopathy. It increases the risk of abnormal heart rhythms and sudden cardiac death. Those affected may have episodes of syncope. The abnormal heart rhythms seen in those with Brugada syndrome often occur at rest. They may be triggered by a fever.

<span class="mw-page-title-main">Mitral valve prolapse</span> Medical condition

Mitral valve prolapse (MVP) is a valvular heart disease characterized by the displacement of an abnormally thickened mitral valve leaflet into the left atrium during systole. It is the primary form of myxomatous degeneration of the valve. There are various types of MVP, broadly classified as classic and nonclassic. In severe cases of classic MVP, complications include mitral regurgitation, infective endocarditis, congestive heart failure, and, in rare circumstances, cardiac arrest.

<span class="mw-page-title-main">Arrhythmogenic cardiomyopathy</span> Medical condition

Arrhythmogenic cardiomyopathy (ACM), arrhythmogenic right ventricular dysplasia (ARVD), or arrhythmogenic right ventricular cardiomyopathy (ARVC), most commonly is an inherited heart disease.

Hypertrophic cardiomyopathy is a condition in which muscle tissues of the heart become thickened without an obvious cause. The parts of the heart most commonly affected are the interventricular septum and the ventricles. This results in the heart being less able to pump blood effectively and also may cause electrical conduction problems. Specifically, within the bundle branches that conduct impulses through the interventricular septum and into the Purkinje fibers, as these are responsible for the depolarization of contractile cells of both ventricles.

<span class="mw-page-title-main">Restrictive cardiomyopathy</span> Medical condition

Restrictive cardiomyopathy (RCM) is a form of cardiomyopathy in which the walls of the heart are rigid. Thus the heart is restricted from stretching and filling with blood properly. It is the least common of the three original subtypes of cardiomyopathy: hypertrophic, dilated, and restrictive.

SCN5A Protein-coding gene in the species Homo sapiens

Sodium channel protein type 5 subunit alpha, also known as NaV1.5 is an integral membrane protein and tetrodotoxin-resistant voltage-gated sodium channel subunit. NaV1.5 is found primarily in cardiac muscle, where it mediates the fast influx of Na+-ions (INa) across the cell membrane, resulting in the fast depolarization phase of the cardiac action potential. As such, it plays a major role in impulse propagation through the heart. A vast number of cardiac diseases is associated with mutations in NaV1.5 (see paragraph genetics). SCN5A is the gene that encodes the cardiac sodium channel NaV1.5.

<span class="mw-page-title-main">Athletic heart syndrome</span> Medical condition

Athletic heart syndrome (AHS) is a non-pathological condition commonly seen in sports medicine in which the human heart is enlarged, and the resting heart rate is lower than normal.

<span class="mw-page-title-main">Catecholaminergic polymorphic ventricular tachycardia</span> Medical condition

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited genetic disorder that predisposes those affected to potentially life-threatening abnormal heart rhythms or arrhythmias. The arrhythmias seen in CPVT typically occur during exercise or at times of emotional stress, and classically take the form of bidirectional ventricular tachycardia or ventricular fibrillation. Those affected may be asymptomatic, but they may also experience blackouts or even sudden cardiac death.

<span class="mw-page-title-main">Takotsubo cardiomyopathy</span> Sudden temporary weakening of the heart muscle

Takotsubo cardiomyopathy or takotsubo syndrome (TTS), also known as stress cardiomyopathy, is a type of non-ischemic cardiomyopathy in which there is a sudden temporary weakening of the muscular portion of the heart. It usually appears after a significant stressor, either physical or emotional; when caused by the latter, the condition is sometimes called broken heart syndrome.

<span class="mw-page-title-main">Noncompaction cardiomyopathy</span> Congenital disease of heart muscle

Noncompaction cardiomyopathy (NCC) is a rare congenital disease of heart muscle that affects both children and adults. It results from abnormal prenatal development of heart muscle.

<span class="mw-page-title-main">Myosin binding protein C, cardiac</span> Protein-coding gene in the species Homo sapiens

The myosin-binding protein C, cardiac-type is a protein that in humans is encoded by the MYBPC3 gene. This isoform is expressed exclusively in heart muscle during human and mouse development, and is distinct from those expressed in slow skeletal muscle (MYBPC1) and fast skeletal muscle (MYBPC2).

<span class="mw-page-title-main">MYH6</span> Protein-coding gene in the species Homo sapiens

Myosin heavy chain, α isoform (MHC-α) is a protein that in humans is encoded by the MYH6 gene. This isoform is distinct from the ventricular/slow myosin heavy chain isoform, MYH7, referred to as MHC-β. MHC-α isoform is expressed predominantly in human cardiac atria, exhibiting only minor expression in human cardiac ventricles. It is the major protein comprising the cardiac muscle thick filament, and functions in cardiac muscle contraction. Mutations in MYH6 have been associated with late-onset hypertrophic cardiomyopathy, atrial septal defects and sick sinus syndrome.

<span class="mw-page-title-main">Plakophilin-2</span> Protein-coding gene in the species Homo sapiens

Plakophilin-2 is a protein that in humans is encoded by the PKP2 gene. Plakophilin 2 is expressed in skin and cardiac muscle, where it functions to link cadherins to intermediate filaments in the cytoskeleton. In cardiac muscle, plakophilin-2 is found in desmosome structures located within intercalated discs. Mutations in PKP2 have been shown to be causal in arrhythmogenic right ventricular cardiomyopathy.

<span class="mw-page-title-main">Ankyrin-2</span> Protein-coding gene in the species Homo sapiens

Ankyrin-2, also known as Ankyrin-B, and Brain ankyrin, is a protein which in humans is encoded by the ANK2 gene. Ankyrin-2 is ubiquitously expressed, but shows high expression in cardiac muscle. Ankyrin-2 plays an essential role in the localization and membrane stabilization of ion transporters and ion channels in cardiomyocytes, as well as in costamere structures. Mutations in ANK2 cause a dominantly-inherited, cardiac arrhythmia syndrome known as long QT syndrome 4 as well as sick sinus syndrome; mutations have also been associated to a lesser degree with hypertrophic cardiomyopathy. Alterations in ankyrin-2 expression levels are observed in human heart failure.

<span class="mw-page-title-main">Ischemic cardiomyopathy</span> Medical condition

Ischemic cardiomyopathy is a type of cardiomyopathy caused by a narrowing of the coronary arteries which supply blood to the heart. Typically, patients with ischemic cardiomyopathy have a history of acute myocardial infarction, however, it may occur in patients with coronary artery disease, but without a past history of acute myocardial infarction. This cardiomyopathy is one of the leading causes of sudden cardiac death. The adjective ischemic means characteristic of, or accompanied by, ischemia — local anemia due to mechanical obstruction of the blood supply.

<span class="mw-page-title-main">Sports cardiology</span>

Sports cardiology is an emerging subspecialty field of Cardiology. It may also be considered a subspecialty field of Sports medicine, or alternatively a hybrid subspecialty that spans cardiology and sports medicine. Emergency medicine is another medical specialty that has some overlap with Sports Cardiology. Sports cardiology is now considered to be a distinct subspecialty in Europe and the USA, with a core curriculum developed in both regions. In Europe it has traditionally been grouped under Preventive Cardiology, but the subspecialty of Sports Cardiology is now considered a distinct field. In the USA, it has developed from being a special interest area to a distinct subspecialty as well.

References

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  2. ↑ Hastings JL, Levine BD (March 2012). "Syncope in the athletic patient". Prog Cardiovasc Dis. 54 (5): 438–44. doi:10.1016/j.pcad.2012.02.003. PMID   22386295.
  3. 1 2 Maron, Barry J. (September 11, 2003). "Sudden Death in Young Athletes". New England Journal of Medicine. 349 (11): 1064–1075. doi:10.1056/NEJMra022783. PMID   12968091. S2CID   6487670.
  4. ↑ Maron, BJ; Estes, NAM III (March 2010). "Commotio cordis". New England Journal of Medicine. 362 (10): 917–927. doi:10.1056/NEJMra0910111. PMID   20220186.
  5. ↑ "Position Statement on Commotio Cordis". US Lacrosse. January 2008. Retrieved 22 February 2017.
  6. 1 2 3 Ferreira M, Santos-Silva PR, de Abreu LC, Valenti VE, Crispim V, Imaizumi C, Filho CF, Murad N, Meneghini A, Riera AR, de Carvalho TD, Vanderlei LC, Valenti EE, Cisternas JR, Moura Filho OF, Ferreira C (Aug 3, 2010). "Sudden cardiac death athletes: a systematic review". Sports Med Arthrosc Rehabil Ther Technol. 2: 19. doi: 10.1186/1758-2555-2-19 . PMC   2923123 . PMID   20682064.
  7. ↑ Maron BJ, Carney KP, Lever HM, Lewis JF, Barac I, Casey SA, Sherrid MV (March 2003). "Relationship of race to sudden cardiac death in competitive athletes with hypertrophic cardiomyopathy". Journal of the American College of Cardiology. 41 (6): 974–980. doi: 10.1016/S0735-1097(02)02976-5 . PMID   12651044.
  8. ↑ La Gerche, André; Brosnan, Maria J. (January 3, 2017). "Cardiovascular Effects of Performance-Enhancing Drugs". Circulation. 135 (1): 89–99. doi: 10.1161/CIRCULATIONAHA.116.022535 . PMID   28028062.
  9. ↑ Moore JR, Leinwand L, Warshaw DM (Jul 20, 2012). "Understanding cardiomyopathy phenotypes based on the functional impact of mutations in the myosin motor". Circ Res. 111 (3): 375–85. doi:10.1161/CIRCRESAHA.110.223842. PMC   3947556 . PMID   22821910.
  10. ↑ Westfal RE, Reissman S, Doering G (Jul 1996). "Out-of-hospital cardiac arrests: an 8-year New York City experience". Am J Emerg Med. 14 (4): 364–8. doi:10.1016/S0735-6757(96)90050-9. PMID   8768156.
  11. ↑ de Vreede-Swagemakers JJ, Gorgels AP, Dubois-Arbouw WI, van Ree JW, Daemen MJ, Houben LG, Wellens HJ (Nov 1997). "Out-of-hospital cardiac arrest in the 1990s: a population-based study in the Maastricht area on incidence, characteristics and survival". J Am Coll Cardiol. 30 (6): 1500–5. doi:10.1016/s0735-1097(97)00355-0. PMID   9362408.
  12. ↑ Kainulainen K, Karttunen L, Puhakka L, Sakai L, Peltonen L (January 1994). "Mutations in the fibrillin gene responsible for dominant ectopia lentis and neonatal Marfan syndrome". Nat. Genet. 6 (1): 64–9. doi:10.1038/ng0194-64. PMID   8136837. S2CID   21910482.
  13. ↑ Dietz HC, Loeys B, Carta L, Ramirez F (November 2005). "Recent progress towards a molecular understanding of Marfan syndrome". Am J Med Genet C Semin Med Genet. 139C (1): 4–9. doi:10.1002/ajmg.c.30068. PMID   16273535. S2CID   25825152.
  14. ↑ Armon K, Bale P (June 2012). "Identifying heritable connective tissue disorders in childhood". Practitioner. 256 (1752): 19–23, 2–3. PMID   22916581.
  15. ↑ Demak, Richard (February 17, 1986). "Marfan Syndrome: A Silent Killer". Sports Illustrated. Retrieved February 12, 2021.
  16. ↑ Raju H, Alberg C, Sagoo GS, Burton H, Behr ER (Nov 21, 2011). "Inherited cardiomyopathies" (PDF). BMJ. 343: d6966. doi:10.1136/bmj.d6966. PMID   22106372. S2CID   35135113.
  17. 1 2 Link, MS; Estes, NAM III (May 2012). "Sudden Cardiac Death in the Athlete". Circulation. 125 (20): 2511–2516. doi: 10.1161/CIRCULATIONAHA.111.023861 . PMID   22615422.
  18. ↑ Zeltser I, Cannon B, Silvana L, Fenrich A, George J, Schleifer J, Garcia M, Barnes A, Rivenes S, Patt H, Rodgers G, Scott W (Jun 15, 2012). "Lessons learned from preparticipation cardiovascular screening in a state funded program". Am J Cardiol. 110 (6): 902–8. doi:10.1016/j.amjcard.2012.05.018. PMID   22704711.
  19. ↑ Harmon KG, Asif IM, Klossner D, Drezner JA (April 2011). "Incidence of sudden cardiac death in National Collegiate Athletic Association athletes". Circulation. 123 (15): 1594–1600. doi: 10.1161/CIRCULATIONAHA.110.004622 . PMID   21464047.
  20. ↑ Chugh SS, Reinier K, Teodorescu C, Evanado A, Kehr E, Al Samara M, Mariani R, Gunson K, Jui J (Nov–Dec 2008). "Epidemiology of sudden cardiac death: clinical and research implications". Prog Cardiovasc Dis. 51 (3): 213–28. doi:10.1016/j.pcad.2008.06.003. PMC   2621010 . PMID   19026856. For the world (total population approx. 6,540,000,000), the estimated annual burden of sudden cardiac death would be in the range of 4–5 million cases per year.
  21. ↑ Asif, Irfan M.; Harmon, Kimberly G. (2017-02-01). "Incidence and Etiology of Sudden Cardiac Death: New Updates for Athletic Departments". Sports Health. 9 (3): 268–279. doi:10.1177/1941738117694153. ISSN   1941-7381. PMC   5435153 . PMID   28452637.
  22. ↑ Harmon, Kimberly G.; Asif, Irfan M.; Maleszewski, Joseph J.; Owens, David S.; Prutkin, Jordan M.; Salerno, Jack C.; Zigman, Monica L.; Ellenbogen, Rachel; Rao, Ashwin; Ackerman, Michael J.; Drezner, Jonathan A. (2015-07-07). "Incidence, Etiology, and Comparative Frequency of Sudden Cardiac Death in NCAA Athletes: A Decade in Review". Circulation. 132 (1): 10–19. doi:10.1161/CIRCULATIONAHA.115.015431. ISSN   0009-7322. PMC   4496313 . PMID   25977310.
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