Heartbreak on the Field

Sudden Cardiac Death in Athletes: Etiology and Prevention

Introduction

Recently, headlines of athletes experiencing sudden death while on the field have become increasingly common. The 2015 European Society of Cardiology (ESC) guidelines, for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death (SCD), define SCD as an unexpected, non-traumatic death within an hour of onset of symptoms in patients with a  pre-existing fatal cardiac condition. During an autopsy the following causes could be identified as the reason of sudden death: cardiac or vascular anomaly, or an arrhythmic event. (1) There is a considerably disparity in the reported cases of  SCD in athletes. Some reports suggest 1 athlete in 39,000 cases per year, while others report 1 athlete in 281,000 cases per year. (2) The risk of SCD increases with age and is common in male athletes. The higher incidence of SCD in male athletes is due to the following reasons:

1. Physiological adaptions of the cardiac muscles due to exercise;

2. Hormonal factors (such as lower amount of oestrogen, which is suppose to be a cardio-protective hormone);

3. Psychological factors (including a tendency to reach exhaustion and high prevalence of substance abuse in male athletes). (3)

Impact of Different Sports on Heart Physiology

Sports can be divided broadly into categories: static and dynamic.

Static sports primarily rely on the efficiency of stabiliser muscles in the body (eg- core muscles of the abdomen). High intensity contraction of these muscles leads to increase in the blood pressure, resulting in a higher afterload on the left ventricle.

Dynamic sports usually depends on factors such as, repeated contraction of large muscle groups and maximal aerobic power of the cardiovascular system.  This leads to an increase in the volume load on the left ventricle. This aspect of sport is often associated with adverse cardiovascular events.  The following table will help clarify the classification of various sporting activities. This classification is provided by American Heart Association (AHA)/American College of Cardiology (ACC) and integrates data from major international competitions such as the Commonwealth Games, Asian Games, Southeast Asian Games, and the Paralympics, ensuring it reflects a broad range of regions across the world. (4)

* Also included in Para Sports (4)

Etiology of Sudden Cardiac Death

Common Causes of SCD in Young Athletes (< 35 years) (5)(6)

Common Causes of SCD in Masters Athletes (> 35 years) (6)

Prevention Strategy

A. Pre-Participation Screening

Etiological factors that lead to sudden cardiac arrest, rarely predispose as a red flag. Therefore, pre-participation screening is crucial in the diagnosis of pre-setting cardiovascular disease. The AHA and ACC  recommend that cardiovascular screening begin with a detailed medical history and a thorough physical assessment. Along with this, a resting 12-lead electrocardiogram (ECG) is also recommended by the European Society of Cardiology (ESC) and the International Olympic Committee (IOC). (7)

The following checklist is a quick guide to pre-participation screening: 

1. Medical History: 

• History of chest discomfort, shortness of breath or syncope, and decline in sports performance.

• Family history related to cardiovascular dysfunction. 

2. Physical assessment: Cardiovascular examination. 

3. 12-Lead ECG

If any abnormal findings are noted in the examination, then:

4. 2-D Echocardiogram: 

• MRI

• Stress Test

• Ambulatory Rhythm Monitoring 

• Genetic Test (7)

Clinicians unaccustomed to interpreting the ECG of an athlete can often perceive exercise-induced physiological findings as pathological. For example:

• Isometric exercise - Physiological left ventricular hypertrophy with wall thickness up to 12-14 mm range. This range is similar to a pathological condition of mild hypertrophic cardiomyopathy (HCM).

• Endurance training - Physiological left ventricular dilation which can be misinterpreted as pathological dilated cardiomyopathy. 

Therefore, it is crucial that a team of expert cardiologists experienced with athletic patients, manage such cases. Cardiopulmonary exercise testing holds the key to managing such cases. To retain the sensitivity and optimise the specificity, several protocols and expert statements have ben proposed, which lead to a reduction in false positive reports. (7)

B. Athlete Education

1. Performance-enhancing drugs: Athletes’ determination to improve performance, outpace competitors, and recover faster often pushes them towards the use of substances. However, when perforce enhancing drugs are used without proper supervision, they can lead to severe consequences, including sudden cardiac death. Therefore athletes should discuss the risks and benefits of these substances with their doctors before use. (2)

2. Channelopathies: Due to the availability of improved medications for managing channelopathies, AHA and ACC guidelines now allow athletes to participate in sports. However, athletes must be educated on the importance of regular checkups and the use of appropriate medications. (2)

To summarise, different sports place varying demands on the cardiovascular system. Owing to the possible fatal risk of sudden cardiac deaths in athletes, proactive screening of the athletes is far more effective than reactive measures.

References

1. Kochi AN, Vettor G, Dessanai MA, Pizzamiglio F, Tondo C. Sudden Cardiac Death in Athletes: From the Basics to the Practical Work-Up. Medicina (Kaunas). 2021;57(2):168. Published 2021 Feb 14.

2. Ghani U, Farooq O, Alam S, Khan MJ, Rahim O, Rahim S. Sudden Cardiac Death in Athletes: Consensuses and Controversies. Cureus. 2023;15(6):e39873. Published 2023 Jun 2.

3. Han J, Lalario A, Merro E, et al. Sudden Cardiac Death in Athletes: Facts and Fallacies. J Cardiovasc Dev Dis. 2023;10(2):68. Published 2023 Feb 5.

4. Wang L, Yeo TJ, Tan B, et al. Asian Pacific Society of Cardiology Consensus Recommendations for Pre-participation Screening in Young Competitive Athletes. Eur Cardiol. 2021;16:e44. Published 2021 Nov 8.

5. Erickson CC, Salerno JC, Berger S, et al. Sudden Death in the Young: Information for the Primary Care Provider. Pediatrics. 2021;148(1):e2021052044.

6. Prakash K, Swarnakari KM, Bai M, et al. Sudden Cardiac Arrest in Athletes: A Primary Level of Prevention. Cureus. 2022;14(10):e30517. Published 2022 Oct 20.

7. Wasfy MM, Hutter AM, Weiner RB. Sudden Cardiac Death in Athletes. Methodist Debakey Cardiovasc J. 2016;12(2):76-80.