CHAPTER KEY WORDS

• Commotio cordis
  
• Hypertrophic cardiomyopathy
  
• Supraventricular tachycardia
  
• Wolff-Parkinson-White syndrome

CHAPTER SCENARIO

A 20-year-old male college basketball player collapses during a game while running down the court. He then appears to have seizure-like activity, with occasional gasping for air. He had a preparticipation physical before the season, with no concerning findings, and he has no family history of sudden cardiac death or arrhythmias.

The basketball player was assumed to be in cardiac arrest due to the sudden collapse and irregular breathing; thus, the athletic trainer started cardiopulmonary resuscitation (CPR) immediately. Another staff member at the school retrieved the automated external defibrillator (AED), and, after placement of the pads, a shock was recommended. The athletic trainer administered the shock and immediately resumed CPR. In 2 minutes, a pulse check revealed a bounding femoral pulse. The player soon began breathing on his own.

SCENARIO RESOLUTION

Upon emergency medical services (EMS) arrival, an electrocardiogram (EKG) was obtained that showed prominent Q waves in multiple leads and criteria for left ventricular hypertrophy. Given the clinical situation and EKG findings, hypertrophic cardiomyopathy was suspected. The player was transferred to the hospital, and, after further evaluation by the cardiology team, he had successful placement of an implantable cardioverter defibrillator (ICD) with no further episodes of syncope or cardiac arrest.

INTRODUCTION

This chapter will discuss cardiovascular emergencies that are common or important causes of death and disability in athletes. The focus is on sudden cardiac arrest (SCA), including both congenital and acquired causes, the importance of immediate recognition, and the principles of management. The impact of exercise on short- and long-term cardiovascular health is discussed. Finally, the chapter reviews the most common cardiac dysrhythmias that cause symptoms or sudden death in athletes.

Sudden cardiac death (SCD) has become a commonly recognized phenomenon in athletics today. It is defined as death of primary cardiac etiology, occurring within 1 hour of witnessed symptom onset and within 24 hours if the incident is unwitnessed. EKG is the best current screening tool1; however, no screening interventions have proven to totally eliminate SCA in athletes.² Most individuals have no signs or symptoms prior to the incident, and this is a key reason why prevention and screening are difficult in this population.³

An Athlete’s Heart

Athletic conditioning is known to cause cardiac remodeling, with corresponding EKG changes, and must be differentiated from pathologic entities.⁴ The Seattle criteria were created to assist physicians and health care providers in determining concerning versus normal physiologic EKG findings.⁵ Common changes seen on the EKGs of athletes are shown in Table 4-1. Normal exercise results in physiologic left ventricular hypertrophy; however, this should be differentiated from pathologic hypertrophy, such as hypertrophic and hypertensive cardiomyopathy. Eccentric hypertrophy is due to compensation for an increased circulating volume, with creation of sarcomeres in series, with resultant elongation of myocytes. This often develops after dynamic exercise, much like that in football and soccer, causing an increase in the left ventricular cavity. Static exercise, such as weight lifting, causes concentric hypertrophy, with an unchanged size of the left ventricular cavity.^6,7 This is due to new sarcomeres being created in parallel, versus in series, from chronic pressure overload, resulting in a thickened myocardium. Concentric hypertrophy is commonly seen in persons with chronically elevated blood pressure due to the heart having to pump against an increased after-load. The amount of hypertrophy correlates to the risk of fatal arrhythmias and SCD.⁷

Incidence

Most SCAs occur during or immediately after exercise.³ The incidence of SCA is always a moving target, but ranges between 1 in 65,000 and 1 in 200,000 athlete-years.⁸ For high school and college athletes specifically, most recent data have published the death rate to be 1 in 50,000 to 1 in 80,000.⁹ Ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT) are the most common cardiac rhythms identified in out-of-hospital cardiac arrest. Pulseless electrical activity (PEA) is less common with a higher mortality rate.¹⁰

Etiology

Most sports-related SCDs occur in individuals older than 35 years.¹¹ In National College Athletic Association athletes, SCA is the leading cause of death during exercise,¹² with the highest rate occurring in male basketball players.¹³ Male athletes are more likely to be affected compared to females (male to female ratio 5:1),¹⁴ but survival rates have been relatively similar between the sexes. A recent study found that basketball and football account for more than half of SCAs in the high school and college-aged athlete.¹⁵ In marathon runners, most SCA cases are seen in the final 4 miles of the race.¹⁶ SCA has also been found to occur almost 4 times more commonly in nonorganized athletic activities compared to organized activities, and more than one-third of those cases were due to coronary artery disease (CAD) in individuals 35 to 45 years of age.¹⁷

The primary causes of SCD are different in athletes who are less than 35 years of age compared to those who older than 35 years of age. In the younger population, a structurally normal heart is the most common finding on autopsy.^3,9,13,18,19 Commonly identified etiologies are shown in Table 4-2.^18–20

The leading cause of death in athletes is due to SCA and is usually prompted by the increased physiologic demands of exercise in those with preexisting cardiac conditions.⁹ More than 80% of the cardiac deaths in athletes have been associated with physical exertion.²¹ Multiple case reports have linked anabolic steroid use to cardiac arrest in body builders.^22–24 When referring to patients older than 35 years, most SCDs are caused by CAD, compared to younger individuals, where arrhythmias and inherited abnormalities are more common.^20,25,26 With a 33% increase in the number of Americans over the age of 65 over the past decade, which is expected to double by 2060,²⁷ SCA could become a more common entity.

Hypertrophic Cardiomyopathy

One of the congenital etiologies linked to SCD in young athletes is hypertrophic cardiomyopathy (HCM), which causes asymmetric thickening of the ventricular septum in 90% of affected individuals, and less commonly involves hypertrophy of the left ventricular wall. Although this condition is inherited in an autosomal-dominant pattern, with an average presentation in the third decade of life, it unfortunately can also occur sporadically without any preceding family history.

Unlike other causes of hypertrophy, in which myocytes grow in an orderly and uniform fashion, patients with HCM suffer from a genetic mutation that causes myocyte disarray, with disorderly cell growth and fibrosis. This leads to diastolic dysfunction and arrhythmias. Figure 4-1 shows classic changes that can be seen on EKG in these patients. The first sign or symptom of HCM may be VF, resulting in SCD. A history of exertional syncope or a positive family history of SCD should prompt further cardiac workup. This condition is more challenging to recognize because these patients routinely have a normal physical examination and are asymptomatic.^7,28

HCM can occur with or without outflow tract obstruction. In patients with no outflow tract obstruction, cardiac hypertrophy causes increased wall stiffness and diastolic dysfunction. The resultant elevated end-diastolic pressure creates back pressure throughout the cardiopulmonary system, leading to dyspnea on exertion. Patients with outflow tract obstruction differ in their pathophysiology. A hypertrophied septum causes obstruction of the lower ventricle outflow tract, which is amplified by high demand and is more so when combined with intravascular volume depletion commonly seen in athletes. This dehydration causes a decrease in the size of the lower ventricle chamber, bringing the hypertrophied septum and anterior leaflet of the mitral valve closer together, resulting in outflow obstruction.⁷ This can lead to syncope from transiently decreased cerebral blood flow.

These patients can have exercise-induced cardiac ischemia, which, over time, causes myocardial fibrosis and cell death.²⁹ This, in combination with the unorganized hypertrophic changes, can predispose an individual to further atrial and ventricular arrhythmias as well as heart failure. The hypertrophy in HCM decreases compliance, which differs from the hypertrophy occurring with a seasoned athlete, who has no focal hypertrophy and maintains a normal left ventricle cavity size, with no left atrial enlargement.²⁸

Beta blockers are the typical therapy for individuals with HCM, improving diastolic filling by decreasing chronotropy and inotropy. They also allow for a decrease in the left ventricular outflow tract pressure gradient.^7,28 However, pharmacologic therapy alone does not prevent SCD, which has led to the advent of ICD placement to prevent fatal arrhythmias in these patients.^7,30

Arrhythmogenic Right Ventricular Cardiomyopathy

Another well-known cause of SCD is arrhythmogenic right ventricular cardiomyopathy (ARVC). ARVC involves the infiltration and replacement of the myocardium and the His-Purkinje bundle with adipose and fibrous tissue, classically in the right ventricle.^29,31 Because of this pathology, it is associated with arrhythmias, heart failure, and SCD.³¹ The incidence is highest in the second to fifth decades of life.³² Patients can have palpitations and syncope; however, unfortunately, SCD can be the first symptom, like many of the other conditions discussed in this chapter.³¹ One study found that nearly one-quarter of SCDs that occurred in adolescents and young adults during sports were due to ARVC from an exercise-induced catecholamine increase.^33,34 However, another study found that of the individuals diagnosed with ARVC, most died during normal daily activities or when sedentary.29 Treatment consists of placement of an ICD.^32,33

The presence of an anomalous coronary artery is another cause of SCD in athletes and was found in one study to account for 17% of deaths.21 The most common abnormality is the occurrence of the left coronary artery origin from the right sinus of Valsalva. This anomalous artery can be constricted when passing between the aorta and pulmonary artery, causing poor cardiac perfusion. The condition can become worse with exertion, given the increased demand on the heart, leading to VF and SCD. Anomalous coronary arteries are ultimately corrected with surgical intervention.³⁵

Long and Short QT Syndrome

Long QT syndrome can be congenital or acquired (Figure 4-2). Congenital causes involve loss of function mutations in potassium channels and gain of function mutations in sodium channels.³⁶ In elite athletes, the prevalence of prolonged QT is 0.4%.³⁷ Numerous medications, including many antiarrhythmics, antibiotics, and antipsychotics, can cause a prolonged QT interval (Table 4-3).³⁷ This condition increases the risk of pVT, also known as Torsades de pointes, with precipitation into VF.¹⁰ Torsades de pointes is a cardiac rhythm that necessitates prompt treatment (Figure 4-3). The first-line therapy is magnesium sulfate and should be given as soon as possible when this rhythm is identified.

Similar to individuals with a prolonged QT, those with a short QT interval are at risk for arrhythmias, both atrial and ventricular (Figure 4-4). This is caused by a mutation in the potassium channel gene.³⁵ The first symptom can be atrial fibrillation or, unfortunately, SCD.³⁸ Patients with this condition are more prone to arrhythmia on exertion due to the catecholamine surge that occurs with the tachycardia of exercise. This causes an even shorter QT interval, leading to deadly arrhythmias.³⁹

Brugada Syndrome

Another cardiac ion channelopathy is Brugada syndrome. In this condition, a sodium channel abnormality allows for a greater potassium efflux from cells compared to sodium influx.⁴⁰ This causes the well-recognized cove-shaped ST-segment elevation in the right precordial leads on EKG (Figure 4-5). Unfortunately, an athlete’s heart can mimic those changes seen in Brugada syndrome; thus, EKG criteria must not be used in isolation for this diagnosis—it must also be based on clinical criteria.⁴¹ Many patients might not even have any EKG changes. However, under the right circumstances, such as a febrile state, hypothermia, hyper- or hypokalemia, hypercalcemia, or cocaine and alcohol toxicity, a patient can experience sudden syncope with decompensation into VF and SCD.³⁵ Unlike the other causes of SCD, this syndrome does not typically present itself during exercise and occurs mostly during rest.41 Therapy involves placement of an ICD.³⁵

Commotio Cordis

Picture a baseball pitcher getting hit in the chest by a line drive. He suddenly collapses and is not moving. What do you do? Commotio cordis occurs with ball-related sports, such as baseball and lacrosse, when there is blunt trauma to the precordium. It has become a more widely recognized etiology of SCD in recent decades. Many of these individuals are found to be in VF and require the same treatment and resuscitation as other patients with this rhythm.^42–44 The location and timing of the impact to the chest is important for development of commotio cordis. The impact must occur on the chest wall directly over the heart during the upslope of the T wave in the cardiac cycle (Figure 4-6).^42,45 Smaller spherical objects are more likely to cause SCA due to a sudden increase in left ventricular pressure, resulting in VF.^45,46 This phenomenon was thought to occur more in younger athletes compared to older individuals due to the increased rate of participation in ball-related sports.⁴³ However, more recent data suggest that the size of an individual is likely the main factor contributing to the increased incidence in younger athletes.⁴⁷ Although previously thought to be shielding, chest protectors have been shown to not be effective in the prevention of SCA from commotio cordis.⁴⁸ Individuals who experience SCA secondary to commotio cordis can resume regular activity if no predisposing cardiac abnormality is identified.⁴⁹

Commotio cordis differs from cardiac contusion, which occurs after blunt trauma, such as a motor vehicle accident, causing structural cardiac damage.⁴² This could include contusion of the myocardium, cardiac chamber rupture, or heart valve disruption and can lead to ventricular arrhythmias. Isolated asymptomatic tachycardia also can be associated with myocardial contusion and might be the only sign of cardiac damage.⁴⁴ At collision speeds of greater than 50 mph, SCD is more likely to be due to structural cardiac damage rather than commotio cordis.⁵⁰

Myocarditis and Pericarditis

Myocarditis is defined as inflammation of the heart muscle, ultimately leading to cell death. The most common etiology is the Coxsackie B virus. Symptoms include chest discomfort, dyspnea, peripheral edema, and fatigue. Cardiogenic shock may occur in severe cases. Treatment is mainly symptomatic with close observation of cardiac function. After clinical resolution, the patient should refrain from vigorous activity for 6 months, have no signs of arrhythmia, and have normal cardiac function prior to return to activity.⁵¹

Pericarditis involves inflammation of the pericardium that surrounds the heart. Pericarditis is typically idiopathic in origin, but can also be due to a viral infection, much like myocarditis. To make the diagnosis of pericarditis, 2 of 4 clinical criteria are necessary: positional chest pain (eg, pain typically better when sitting than supine), pericardial friction rub, EKG changes (eg, non-vascular distribution of ST elevations and PR segment depressions), and new or worsening pericardial effusion.⁵² Both myocarditis and pericarditis can present similarly; thus, a troponin value is useful in determining the diagnosis.

Pericarditis alone should not have any increase in troponin value compared to myocarditis, which should have a moderately elevated level. However, pericarditis should not be thought of as less dangerous, as these patients can develop cardiac tamponade acutely due to large pericardial effusion and in later stage due to constrictive pericarditis. This is due to poor ventricular filling during diastole from a rigid, fibrous pericardium that can develop after an episode of acute pericarditis and can lead to decreased stroke volume and cardiac output, resulting in hypotension.7 If pericarditis is diagnosed in an otherwise well-appearing patient, the first-line therapy is non-steroidal anti-inflammatory drugs. Athletes should refrain from physical activity until symptoms have resolved and there are no longer clinical or laboratory signs of disease, such as resolution of pericardial effusion on echocardiogram and normalization of erythrocyte sedimentation rate and C-reactive protein.⁵³

Related posts:

6 Respiratory Emergencies 2 Mass Casualty Incidents 8 Shock 5 Endocrine Emergencies 12 Abdominal Emergencies 13 Emergencies Related to Conditioning and Exercise

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