Case Example

A 55-year-old male master triathlete presents to the emergency department with new chest tightness, dynamic ECG changes, and increased troponin. Subsequent cardiac angiography demonstrates a 90% left circumflex lesion and he is now status-post successful percutaneous intervention. Recovery is uneventful, left ventricular function remains preserved, and he is discharged from the hospital within 72 hours. At his initial sports cardiology clinic follow-up visit, his first question focuses on the return to competitive exercise.

Background

While hypothetical in description, the case example highlighted above is classic for master athletes with coronary artery disease (CAD). For the sports cardiologist, managing the exercise prescription for the athlete with CAD post-myocardial infarction (MI) is both complex and challenging because of the absence of rigorous, evidenced-based data taken from the master athletic population. It is no surprise that in the United States, as participation rates within recreational competitive athletics continue to rise,¹ so too has the population of master recreational endurance athletes with cardiac risk factors and established cardiac disease. While these trends should be embraced because of the established long-term cardiovascular benefits of habitual exercise, we are also aware that master athletes with CAD harbor a paradoxical increased risk of acute cardiac events during vigorous physical exertion.² Indeed, underlying occult CAD with subsequent acute myocardial ischemia is the primary etiology for sudden cardiac arrests and deaths in master athletes.^3,4 Thus, sports cardiologists must be proficient in both estimating cardiovascular risk among healthy master athletes and also assisting in the management of exercise training in athletes post-ischemic cardiac events. Unfortunately for master athletes, both of these critically important tasks lack modern, evidenced-based criteria. In this expert analysis, we will review some of the limited data that exist in regard to exercise training in master athletes with CAD, while affirming the critical role of the shared-decision making process with athletic patients.

As a means of relevant background, exercise-related cardiac events are generally defined as those occurring during, or within 1 hour after, vigorous physical exertion (typically defined as exercise requiring six or more metabolic equivalents (METs) or equal to or greater than a VO₂ of 21 mL kg–1 min–1). Competitive recreational exercise is also associated with heightened adrenergic states, thus lesser workloads may further stress the cardiovascular system of older individuals during competition. A summary of select studies examining the risk of cardiac arrest during vigorous physical exertion in those subjects with CAD or possible CAD is shown in Table 1. For master athletes with newly diagnosed CAD, particularly post-MI, sports cardiologists must balance the risk of future events with the goal of most master athletes to resume competitive recreational sport participation.

Table 1: Cardiac Arrest/Sudden Cardiac Death Associated with Exercise in Patients with Coronary Artery Disease

Study	Year	Population	Incidence
Thompson, et al9	1982	Joggers	1 SCD per 396,000 person-hours jogging
Van Camp, et al10	1986	Cardiac Rehabilitation	1 CA per 111,996 patient-hours exercise
Digenio, et al11	1991	Cardiac Rehabilitation	1 CA per 120,000 patient-hours exercise
Vongvanich, et al12	1996	Cardiac Rehabilitation	1 CA per 89,510 patient-hours exercise
Franklin, et al13	1998	Cardiac Rehabilitation	1 CA per 97,418 patient-hours exercise
Albert, et al14	2000	Middle-Aged Men	1 SCD per 19 million person-hours exertion
Kim, et al4	2012	Marathon	0.54 CA per 100,000 runners; 0.39 SCD per 100,000 runners

Current Evidence

While acknowledging master athletes are non-sedentary, establishing a cardiac rehabilitation program post-MI, similar to the non-athletic general population, should still be implemented post-MI or revascularization. Recently, Andersen and colleagues performed a systematic review and meta-analysis re-evaluating the value of cardiac rehabilitation.⁵ In this analysis, 63 randomized placebo-controlled studies, involving 14,486 cardiac rehab participants followed for at least 6 months, were included. Compared to the control data, cardiovascular mortality was reduced by 26% and hospital readmissions were reduced by 18% in patients enrolled in cardiac rehab. There are also important cost implications as a result of appropriate cardiac rehab referrals, most likely because of increased individual medical interactions leading to reduced emergency department visits. In the general non-athletic population, exercise-based cardiac rehabilitation remains underutilized in contemporary cardiology. Perhaps this is because many physicians are uncomfortable with appropriate recommendations for an adequate exercise prescription. It is important for sports cardiologists to not lose sight of the benefits of cardiac rehab and continue to encourage these referrals to our post-MI master athletes as the first step post cardiac event and/or revascularization.

As previously mentioned, guiding the exercise prescription for competitive master athletes with obstructive CAD is challenging because of the paucity of evidenced-based supportive data. Currently, there are no clinical trials focused on the appropriate exercise prescription for master recreational athletes with CAD. Expert consensus recommendations on this topic are available in the American Heart Association and American College of Cardiology (AHA/ACC) Eligibility and Disqualification Recommendations for Competitive Athletes with Cardiovascular Disease (Table 2).⁶ It is recommended that all athletes with CAD undergo maximal functional exercise testing and evaluation of left ventricular function prior to the determination of the appropriate exercise prescription. The time course for exercise-testing athletes post percutaneous intervention (PCI)/MI or coronary artery bypass graft (CABG) surgery in order to define the initial appropriate exercise regimen should be considered the same as for the general population. For those athletes post-PCI, symptom limited exercise testing should be considered within 1-2 weeks. Exercise testing in post-CABG patients should be deferred until the surgical wounds are appropriately healed (approximately 3-4 weeks). These recommendations advise refrainment from competitive athletics for at least 3 months prior to the re-assessment of functional status and cardiac function. For the sports cardiologist, this author's opinion is that functional exercise testing utilizing cardiopulmonary gas exchange measurements should be considered to assist in the determination of the exercise prescription. In addition to basic exercise ECG stress testing measurements (e.g., blood pressure alterations, heart rate rise and recovery, stress ECG changes) and symptom assessment, peak VO₂, the estimated ventilatory threshold, and the derived O₂ pulse may further characterize cardiovascular performance at peak exercise and heart rate training zones for master endurance athletes with CAD. In our experience, master athletes are not satisfied with "general" exercise recommendations and rather appreciate more detailed specifics, sometimes to share with their personal trainers, in adjusting to a new exercise prescription.

Table 2: Summary of Consensus Recommendations Regarding Return to Competitive Athletic Participation in Athletes with Coronary Artery Disease⁶

Risk Category	LV Ejection Fraction	Exercise Tolerance*	Exercise-Induced Ischemia#	Exercise-Induced Arrhythmia	Residual Coronary Stenosis
Minimally Increased	≥50	Normal	None	None	<50%
Substantially Increased	<50	Decreased	Positive	VT	≥50

Duration of medical therapy specific to the "safe" return to competitive exercise is also an issue with sparse data. Acute coronary syndromes generally arise from non-critical atherosclerotic lesions that rupture and initiate an inflammatory cascade and subsequent acute thrombosis.⁷ Prior data suggest that statins may reduce atherosclerotic plaque lipid content and therefore lead to atherosclerotic lesion regression. Specifically, the largest study addressing this question reported atherosclerotic plaque regression for patients on statin therapy.⁸ In this systematic review of 10,235 subjects on statins (wide variety of high potency statins), plaque regression was demonstrated in the carotids, coronaries, and aortic vascular beds after an average time of 19.7 months. In addition, LDL reduction averaged a 40% decrease from baseline. Whether this long-duration approach for plaque stabilization utilizing maximal statin therapy and competitive athletic restriction leads to reduced cardiac risk in master athletes post-MI remains speculative. However, this additional medical strategy, in addition to aggressive management of atherosclerotic risk factors, should at least be considered on an individualized basis and discussed in the shared-decision making process with the athlete.

Shared Decision Making

Perhaps the most important and critical aspect in the guidance of exercise recommendations for master athletes post-MI is the shared-decision making process. The return to vigorous competitive activity after an ischemic cardiac event is wrought with anxiety for both the athlete and sports cardiologist contemplating this complex decision process. While functional exercise testing, current consensus guidelines, and limited evidenced-based science may assist the sports cardiologist in each individualized case, specific psychosocial factors unique to the athlete should not be underestimated or ignored. In addition, the limitations of what we know and don't know must be acknowledged by sports medicine practitioners. The athlete must weigh the risks and extent of their disease with the importance of competitive and strenuous exercise to their mental and psychological well-being. These factors, in combination with the overall risk profile provided by the sports cardiologist, will guide the custom and appropriate exercise prescription for the master athlete with CAD post-MI.

Going back to the management of the master athlete described in the case example; after participation in a cardiac rehab program, we would have proceeded with a maximum, symptom limited functional exercise test followed by a shared decision meeting with the athlete. In addition to the development of the initial customized exercise prescription, this meeting sets the stage for the long-term establishment in the sports cardiology clinic for routine preventive cardiovascular care as well as for exercise guidance.

References

1. Bush S. http://www.runningusa.org/state-of-sport-us-trends-2015.
2. Parker MW, Thompson PD. Assessment and management of atherosclerosis in the athletic patient. Prog Cardiovasc Dis 2012;54:416-22.
3. Thompson PD. The cardiovascular complications of vigorous physical activity. Arch Intern Med 1996;156:2297-302.
4. Jim JH, Malhotra R, Chiampas G, et al. Cardiac arrest during long-distance running races. N Engl J Med 2012;366:130-40.
5. Anderson L, Thompson DR, Oldridge N, et al. Exercise-based cardiac rehabilitation for coronary heart disease. Cochrane Database Syst Rev 2016:DC001800.
6. Thompson PD, Myerburg RJ, Levine BD, Udelson JE, Kovacs RJ. Eligibility and disqualification recommendations for competitive athletes with cardiovascular abnormalities: task force 8: coronary artery disease: a scientific statement from the American Heart Association and American College of Cardiology. J Am Coll Cardiol 2015;66:2406-11.
7. Frink RJ. Chronic ulcerated plaques: new insights into the pathogenesis of acute coronary disease. J Invasive Cardiol 1994;6:173-85.
8. Noyes AM, Thompson PD. A systematic review of the time course of atherosclerotic plaque regression. Atherosclerosis 2014;234:75-84.
9. Thompson PD, Funk EJ, Carleton RA, Sturner WQ. Incidence of death during jogging in Rhode Island from 1975 through 1980. JAMA 1982;247:2535-8.
10. Van Camp SP, Peterson RA. Cardiovascular complications of outpatient cardiac rehabilitation programs. JAMA 1986;256:1160-3.
11. Digenio AG, Sim JG, Dowdeswell RJ, Morris R. Exercise-related cardiac arrest in cardiac rehabilitation. The Johannesburg experience. S Afr Med J 1991;79:188-91.
12. Vongvanich P, Bairey Merz CN. Supervised exercise and electrocardiographic monitoring during cardiac rehabilitation. Impact on patient care. J Cardiopulm Rehabil 1996;16:233-8.
13. Franklin BA, Bonzheim K, Gordon S, Timmis GC. Safety of medically supervised outpatient cardiac rehabilitation exercise therapy: a 16-year follow-up. Chest 1998;114:902-6.
14. Albert CM, Mittleman MA, Chae CU, Lee IM, Hennekens CH, Manson JE. Triggering of sudden death from cardiac causes by vigorous exertion. N Engl J Med 2000;343:1355-61.

Keywords: Sports, Athletes, Myocardial Infarction, Coronary Artery Disease, Physical Exertion, Troponin, Metabolic Equivalent, Heart Rate, Risk Factors, Ventricular Function, Left, Cardiac Rehabilitation, Patient Readmission, Symptom Assessment, Cardiovascular Diseases, Blood Pressure, Exercise Test, Running, Death, Sudden, Cardiac, Coronary Artery Bypass, Angiography, Electrocardiography, Adrenergic Agents, Cohort Studies

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