Cardiologists and others caring for active individuals need to understand the changes common to the athletic heart as well as screening and risk stratification practices of athletes with and without known cardiovascular diseases.^1,2 The heart and vascular system undergo many physiologic changes in response to the demands of exercise characteristic of the athletic heart and it is important to distinguish those physiologic changes from pathology. Here we present an overview of what we believe encompasses the major topics within the field of sports cardiology. Part 2 of this series will focus on the athlete's heart and exercise physiology; Part 3 of this series will focus on current controversies within sports cardiology.

Sports Cardiology

Sports cardiology is an advancing field that encompasses the care of athletes and active individuals with known or previously undiagnosed cardiovascular conditions. It incorporates many aspects of cardiology, such as cardiac imaging, electrophysiology, structural heart disease and exercise physiology.³ As such, a comprehensive sports cardiology program should include physicians with specific knowledge within these fields. The sports cardiology team should include those with expertise in the pediatric heart, especially congenital heart disease and inherited diseases, cardiovascular imagers, electrophysiologists, heart failure specialists and exercise physiologists. These specialists must come together to make comprehensive assessments and recommendations for athletes. Examples include the assessment of exercise-induced cardiac remodeling versus cardiac pathology, the utilization of cardiac MRI, CT and cardiopulmonary exercise testing (CPET) specific for athletic patients, accessing genetic counseling when appropriate, and the determination of sports eligibility and exercise prescriptions for athletes with cardiovascular risk and disease. A close relationship with athletic trainers, coaches, and families is also necessary to maintain a multidisciplinary approach to the care of the athlete. The sports cardiology team will help athletes make informed decisions to allow them to safely and effectively participate in sport.

Evaluation and Treatment of the Symptomatic Athlete

Chest pain in the athlete can have a myriad of causes, benign and malignant. The delineation can often be made based on history and electrocardiogram (ECG). Echocardiography can also be helpful in the initial evaluation by uncovering structural heart disease. Athletes over the age of 35 are more likely to present with atherosclerosis as the underlying cause. Chest pain and syncope or near syncope during exercise typically warrant immediate restriction from sport and evaluation.⁴

Syncope and presyncope can be physiologic responses to exercise such as vasodilation and blood pooling that can lead to transient postural orthostasis. However, more ominous causes such as an arrhythmia need to be ruled out. Evaluation should highlight whether symptoms occurred during or after exercise with the latter more likely to be benign. A thorough physical is paramount while other testing should include the surface ECG, echocardiography, ambulatory rhythm monitoring and maximal exercise testing. Tilt table testing could be considered if initial testing is inconclusive. If clearly exertional syncope, athletes should be restricted from sport until the cause of syncope is identified. At that point, a risks versus benefits discussion should ensue prior to returning to activity.⁵

In addition to primary cardiac diseases, exercise intolerance may be related to a systemic disease process or simply detraining. Basic laboratory evaluations should be performed to rule out anemia, thyroid disorder or metabolic derangements. In addition, ECG, echocardiogram and maximal effort exercise stress test are recommended as part of a complete work-up.⁴ Any athlete with exertional symptoms should be evaluated with stress testing tailored as much as possible to simulate exertion during training/competition.

Common Risk Factors

Atherosclerotic Coronary Artery Disease

Regular exercise has been shown to be protective against the development of atherosclerotic disease. However, much like the general population, ischemic coronary disease remains a common problem even within athletic cohorts. Autopsy based studies suggest that atherosclerotic disease is the most common cause of sudden cardiac death (SCD) in the aging athlete.⁶ Similar to that of the general population, management should focus on risk factor modification. Statin related muscle fatigue may be more common in the athletic population but treatment with lipid lowering agents should remain a priority. There is not yet any data on PCSK9 inhibitors among athletes. Despite a high level of fitness, all athletes who have experienced an acute coronary event should be encouraged to participate in a cardiac rehabilitation program.

Hypertension

Hypertension (HTN) is the most common cardiovascular condition in the healthy athletic population. A thorough evaluation of an athlete should involve a detailed history that includes questions about supplement use as well as over the counter medications. Physical exam must include bilateral brachial blood pressures during each visit. It has also been recommended that athletes with HTN get at least one lower extremity pressure to exclude coarctation of the aorta.⁷ Those with borderline HTN or those with suspected 'white coat' HTN should be encouraged to perform ambulatory blood pressure monitoring. Measurements of blood pressure during exercise may be useful in diagnosing those with masked HTN or to help evaluate effectiveness of ongoing treatment. Treatment of HTN should focus on lifestyle modification and medications whose side effect profile does not negatively affect performance. As such, vasodilators and angiotensin-converting-enzyme inhibitors would be preferred over beta-blockers or diuretics. The 2015 American College of Cardiology/American Heart Association (ACC/AHA) scientific statement describing eligibility criteria for athletes with cardiovascular abnormalities combined with the most recent 2017 definitions for HTN states that those with stage 1 HTN (systolic blood pressure (SBP) 130-139 mmHg or diastolic blood pressure [DBP] 80-89 mmHg) without end organ damage should not be restricted from any competitive sport.^8,9 Those with stage 2 HTN (SBP≥140 mmHg or DBP≥90 mmHg) without evidence of end organ damage should be restricted from sport with particularly high static strain, for example, weightlifting or martial arts, until HTN is controlled.^8-10

Preexisting Cardiovascular Disease, Including Inherited Conditions, Valvular Disease, Arrhythmias and Aortopathies

Diseases of the Heart Muscle

Hypertrophic cardiomyopathy (HCM) is an inherited cardiomyopathy that is characterized by hypertrophy of the left ventricle (LV) not explained by another disease process (e.g., HTN, aortic stenosis). It is often initially suspected based on abnormal T-waves on ECG or identified during screening of family members with HCM. The diagnosis requires echocardiography and, in some cases, cardiac MRI. Exercise testing and short-term heart rate monitoring are part of the initial evaluation. Genetic testing is used for family prognostication once the phenotypic diagnosis is unequivocal. HCM is associated with an increased risk for SCD, with specific criteria for implantable cardiac defibrillator (ICD) placement for any high-risk patient with HCM, not specific to the athlete.¹¹ Exercise was previously thought to increase the risk for SCD; however, a recent study reported that exercise of increasing intensities may be beneficial and potentially even low risk in this population.¹² At present time, consensus recommendations favor restriction from competitive athletics in patients with HCM. However, shared-decision making should be incorporated in cases of newly diagnosed HCM in an athlete as well as most cases of sports participation in athletes with underlying cardiovascular risk or disease. For those who are genotype-positive HCM but phenotype-negative, current recommendations allow for continued competitive sport participation with active surveillance.¹³

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiomyopathy characterized by fatty deposition in the myocardium of the right ventricle but may also involve the LV. Diagnosis is based on a scoring system including imaging, ECG and histopathology findings as well as arrhythmias and family history. Athletes with ARVC should be restricted from competitive and possibly even lower-intensity exercise as exercise has been shown to increase the progression of cardiomyopathy as evidenced by ventricular dilation and arrhythmias.¹³

Myocarditis, pericarditis and myopericarditis are characterized by inflammation of the heart muscle, pericardium, or both, with an increased risk for arrhythmia when the heart muscle is involved. All of these processes require restriction from aerobic exercise until there is evidence of inflammation resolution based on clinical and imaging data, and often a period of close monitoring is then required before returning to full activity.¹³

Congenital Heart Disease

Congenital heart disease is a broad topic that will not be covered in depth in this document. There are specific recommendations for each disease process; overall, most patients with congenital heart disease should be encouraged to exercise, the inherent risks and suggested monitoring are individualized.¹⁴

Diseases of the Heart Valves

Based on consensus recommendations, the severity of valvular heart disease determines the frequency of follow-up and informs the acceptable intensity of exercise in which athletes may participate. This discussion of valvular heart disease can be applied to aortic stenosis, aortic regurgitation (AR), mitral regurgitation (MR) and mitral stenosis.

If the disease is classified as mild, then the majority of athletes are low risk to participate at a competitive level. It is important to still monitor these patients, usually at an annual basis or at onset of symptoms if sooner. An exercise stress test can be helpful at baseline to delineate if a patient is truly asymptomatic and hemodynamically stable during full exertion.

Activity is nearly always restricted for those with severe valvular heart disease until the valve issue is addressed, after which there are certain criteria for those with valve replacement and sport participation. Those with severe MR and severe AR may be cleared to participate in low to moderate intensity sport if they do not have evidence of LV dysfunction, anything more than mild LV dilation or pulmonary HTN (pulmonary HTN only applies to MR).

Athletes with moderate valve disease and valve replacements may participate in varying levels of sport depending on the type of valve replacement (bioprosthetic, mechanical), and if required to take anticoagulation (sports with low risk for bodily collision should be considered). If a valve has been repaired, then athletes may be considered low risk to partake in high intensity sport compared to those with replaced valves. Much of the determination is based on echocardiography parameters including valve disease severity, LV function, patient symptoms and exercise tolerance. As with most discussions between patient and care providers, shared decision-making is essential.¹⁵

Diseases of Electrical System

Tachycardia can take many forms and in all cases a thorough history must assess presence of symptoms (e.g., presyncope, syncope, etc.) and use of drugs (e.g., stimulants). A complete physical exam is required, as could be lab testing, ECG and echocardiogram.

Supraventricular tachycardia, such as atrial fibrillation, atrial flutter and reentrant tachycardias, are common in the athletic population. Evaluation with ECG, ambulatory ECG monitor, echocardiogram and exercise stress testing should be considered for risk stratification. Invasive EP studies may be necessary for additional risk stratification and/or treatment. While pharmacologic therapies are available, catheter ablation is increasingly considered as a first-line treatment option given the procedural success rates and ability to forgo long-term medications. Moreover, athletes tend to have significant side effects from anti-arrhythmic and AV nodal blocking medications.

Ventricular arrhythmias require further evaluation in nearly all circumstances. In these cases, physicians often require evidence of arrhythmia suppression and a long-term monitoring period before permitting return to sport. Rare isolated premature ventricular contractions can often just be observed; however, non-sustained ventricular tachycardia (NSVT) or VT requires restriction from sport and evaluation with ECG, echocardiography and maximal exercise stress testing. Channelopathies are on the differential diagnosis list, such as Brugada syndrome, idiopathic ventricular fibrillation, long QT syndrome and catecholaminergic polymorphic ventricular tachycardia, at which point a geneticist and electrophysiologist should be involved for further guidance.¹⁶ PVCs could be an early manifestation of ARVC. Medical therapy including suppressive medications can be used and where warranted, an ICD may be implanted. After ICD implant, case by case risk-benefit discussions should ensue to jointly decide if an athlete with an ICD can return to partial or full activity or not at all.

Sinus bradycardia is a common finding in the athletic population given the increase in vagal tone; however, resting heart rates below 30 beats per minute while awake, >3 second sinus pauses or symptomatic bradycardia warrant further evaluation. Some forms of atrioventricular block can be normal findings, but Mobitz type II and complete heart block are never normal. Athletes with abnormal findings, in addition to those with right or left bundle branch block, should be evaluated with an ECG monitor, an exercise stress test to evaluate for chronotropic incompetence, and an echocardiogram. In some cases, an invasive electrophysiology study for further risk stratification is necessary. Some athletes will require permanent pacemaker placement, and depending on the level of pacemaker dependence and degree of contact sport participation, may return to activity.⁵

Diseases of the Aorta

There are a number of inherited conditions that can predispose the aorta to dilation or rupture. The most common syndromic aortopathy is Marfan syndrome. The most common associated congenital condition is a native bicuspid aortic valve.¹⁷ The size of the aorta should be evaluated in the context of the athlete's age, sex and height, but even in the largest young athletes, the aortic root rarely exceeds 4 cm in men or 3.4 cm in women. If a syndromic aortopathy is suspected, consultation with a geneticist is recommended.¹⁸ Exercise recommendations for those with inherited aortic conditions remains controversial and incomplete due to a paucity of outcomes data.¹⁹ Individual societies such as the European Society of Cardiology, ACC/AHA and Marfan Foundation are in general agreement that isometric exercise requiring straining or valsalva, contact sports, and competitive dynamic activities should be avoided. It is essential, however, that exercise recommendations not be too stringent so as to discourage a healthy active lifestyle.

Screening

SCD has a low incidence in the athletic population cited as 1/80,000 and 1/50,000 in high school and college athletes, respectively, with variations in these rates based on race, sport and other demographics.²⁰ Despite a low incidence, each occurrence is alarming and further research is needed to better understand the causes. Equally important is having proper emergency training for coaches and other team personnel in basic life support and advanced cardiac life support. Emergency action plans must account for access to automatic external defibrillators (AEDs) and emergency medical services. The most common structural cardiovascular conditions linked to SCD in the young (generally less than 35 years old) athlete include HCM, congenital coronary anomaly and ARVC.²¹ In older athletes, coronary artery disease remains the greatest risk factor. Pre-participation screening focusing on the history and physical exam is recommended for competitive athletes in the United States. The pre-participation examination (PPE) includes a history and physical to identify key findings that would warrant further evaluation, such as symptomatology, family history of SCD or other heart disease, or murmurs on exam. The AHA provides a 14-point PPE template.²¹ A recent meta-analysis found that the sensitivity of the ECG, history and physical examination were 94%, 20% and 9%, respectively, and the specificity was similar in all groups: 93%, 94% and 97%, respectively.²² The ECG is currently not recommended as mandatory for the PPE in the United States, as controversy exists regarding the possibility of false positives and efficacy in terms of mortality reduction. Further issues include the difficulty in standardizing the quality of interpretation as well as large-scale management of mandated ECG screening. Smaller scale ECG screening may be considered with appropriate resources in place.²¹ The PPE may lead to further testing and uncovering underlying disease processes, which can then lead to intervention, closer surveillance, and/or restriction from sport. There are many legal and ethical considerations that surround the shared decision-making process of sports eligibility determination.²³

Specific Athlete Populations

There are unique challenges specific to each age group of athlete. Adolescents and teenagers experience rapid growth and hormonal changes, which can make normal physiologic ranges difficult to determine. Medical decision-making often involves parents or other caregivers, coaches and trainers, all adding complexity to the interaction between provider and patient. Collegiate athletes are suddenly immersed in significantly more rigorous training requirements compared to high school. Professional athletes as well as occupational athletes, such as police officers and active military, often have screening protocols dictated by their respective professional body. Student athletes adjusting to life in college or athletes who are restricted from competition are two cohorts who may undergo significant psychological strain.²⁴ Thus, a comprehensive care team should have access to a sports psychologist. The "weekend warrior" is another type of athlete who presents unique challenges as these patients often suffer from poor conditioning due to inconsistent training and are at high risk for overuse injuries or those caused by improper technique. The largest growth area for the sports cardiologist is in care for the highly active recreational athlete, usually consisting of post-collegians who may have cardiovascular risk factors or underlying cardiac conditions. Developing an individualized exercise prescription can help recreational athletes development a proper and consistent training regimen.²⁵

Enhancing Athlete Performance

Optimized athletic performance is something that can be achieved by natural means or through illegal avenues such as doping. As a sports cardiologist it is important to know the drugs that athletes may be using, their associated risks and how to test and treat in these situations. It is also important to understand which testing can be utilized, such as CPET, to measure an athlete's performance. Exercise prescriptions can be created and monitored based on an athlete's medical history and via testing such as the CPET.

Ethics and Legal System

An important aspect of sports cardiology involves the ethical and legal concerns associated with counseling an athlete about the safety of returning to play. This becomes more complex when an athlete chooses to participate in competitive sports despite a known but unquantifiable risk of cardiovascular damage or even death. Current ACC/AHA guidelines currently advocate for shared decision-making where all involved parties openly discuss what amount of sport participation and risk would be considered reasonable.²⁶

Getting Involved

For cardiologists interested in learning about or becoming more involved in the field of sports cardiology, there are a number of resources. The most comprehensive introduction is available at the yearly ACC Care of the Athletic Heart meeting. At the annual ACC Scientific Sessions, there are always a number of sports cardiology talks, research presentations and an all-section meeting where members of the Sports and Exercise Cardiology member section may meet and greet. Dedicated sports cardiology training programs for fellows-in-training (FITs) interested in this field are beginning to develop with the most established and only accredited sports cardiologoy fellowship program in the US run by Dr. Aaron Baggish at the Massachusetts General Hospital Cardiovascular Performance Program. In addition, ACC.org's Sports and Exercise Cardiology Clinical Topic Collection publishes monthly pieces focused on care of the athlete. Fellows-in-training (FITs) interested in opportunities within the Sports and Exercise cardiology section can contact Chris Driver (Chris Driver cdriver@acc.org).

References

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Clinical Topics: Arrhythmias and Clinical EP, Cardiac Surgery, Cardiovascular Care Team, Congenital Heart Disease and Pediatric Cardiology, Diabetes and Cardiometabolic Disease, Dyslipidemia, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Pericardial Disease, Prevention, Sports and Exercise Cardiology, Valvular Heart Disease, Atherosclerotic Disease (CAD/PAD), Implantable Devices, EP Basic Science, Genetic Arrhythmic Conditions, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Aortic Surgery, Cardiac Surgery and Arrhythmias, Cardiac Surgery and CHD and Pediatrics, Cardiac Surgery and Heart Failure, Cardiac Surgery and VHD, Congenital Heart Disease, CHD and Pediatrics and Arrhythmias, CHD and Pediatrics and Imaging, CHD and Pediatrics and Prevention, CHD and Pediatrics and Quality Improvement, Lipid Metabolism, Nonstatins, Novel Agents, Statins, Acute Heart Failure, Computed Tomography, Echocardiography/Ultrasound, Magnetic Resonance Imaging, Nuclear Imaging, Exercise, Hypertension, Sports and Exercise and Congenital Heart Disease and Pediatric Cardiology, Sports and Exercise and ECG and Stress Testing, Sports and Exercise and Imaging, Mitral Regurgitation

Keywords: Aging, Advanced Cardiac Life Support, American Heart Association, Adolescent, Anemia, Angiotensin-Converting Enzyme Inhibitors, Anti-Arrhythmia Agents, Aorta, Aortic Coarctation, Aortic Valve Insufficiency, Aortic Valve Stenosis, Arrhythmias, Cardiac, Arrhythmogenic Right Ventricular Dysplasia, Atherosclerosis, Athletes, Athletic Performance, Atrial Flutter, Atrial Fibrillation, Atrioventricular Block, Blood Pressure, Blood Pressure Monitoring, Ambulatory, Brugada Syndrome, Cardiac Rehabilitation, Bundle-Branch Block, Bradycardia, Cardiomyopathy, Hypertrophic, Caregivers, Catheter Ablation, Channelopathies, Coronary Artery Disease, Cumulative Trauma Disorders, Chest Pain, Cohort Studies, Death, Sudden, Cardiac, Defibrillators, Decision Making, Diagnosis, Differential, Dilatation, Diuretics, Dizziness, Echocardiography, Electrocardiography, Electrophysiology, Eligibility Determination, Emergency Medical Services, Exercise, Exercise Test, Exercise Tolerance, Genetic Counseling, Genetic Testing, Genotype, Heart Diseases, Heart Failure, Heart Rate, Heart Valve Diseases, Heart Valves, Heart Ventricles, Hydroxymethylglutaryl-CoA Reductase Inhibitors, Hypertrophy, Hypertension, Inflammation, Life Style, Lipids, Long QT Syndrome, Magnetic Resonance Imaging, Lower Extremity, Marfan Syndrome, Mitral Valve Stenosis, Mitral Valve Insufficiency, Muscle Fatigue, Myocarditis, Myocardium, Pacemaker, Artificial, Pericarditis, Pericardium, Physical Examination, Physical Exertion, Tachycardia, Ventricular, Sports, Risk Factors, Specialization, Syncope, Tachycardia, Supraventricular, Tachycardia, Ventricular, Tomography, X-Ray Computed, Vasodilation, Vasodilator Agents, Ventricular Fibrillation, Ventricular Premature Complexes

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