Athletic Field Disasters: Understanding the Risks of Sudden Cardiac Death in Sports

As I am writing this review article, the sports world continues to be in shock from the surreal episode that unfolded during the live Monday Night Football game between the Buffalo Bills and the Cincinnati Bengals last month on January 2, 2023. Following a seemingly routine and innocuous tackle by Bills’ safety, Damar Hamlin, Hamlin collapsed and became lifeless. Sideline trainers and EMS personnel quickly realized that this was not a mundane orthopedic issue that appears so commonly during the course of every NFL game. For unclear reasons, as of this writing, Hamlin required immediate CPR and intubation to address his state of extremis. There are unfortunately a subset of clinical conditions that may never be discovered unless they are unmasked during the throws of some athletic event. Here, I will discuss 4 conditions that may initially present themselves on the athletic field as sudden cardiac death and the crucial role of Advanced Cardiac Life Support (ACLS) in saving lives on the athletic field and beyond. As the old adage goes, “the eyes cannot see what the mind does not know.” If you are unaware of, and/or don’t recognize any of the following four conditions, your patient(s) may suffer dire consequences: (1) hypertrophic cardiomyopathy, (2) coronary artery anomalies, (3) long QT syndrome, and (4) commotio cordis.

Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is one of the many genetic cardiac maladies that can afflict the structure and ultimate function of the heart. This condition is generally characterized by asymmetric hypertrophy and fibrosis of the interventricular septal muscle which precludes normal outflow of blood from the left ventricle into the proximal aorta and further relaxation of the left ventricle precluding normal filling during diastole. As the heart hypertrophies, the risk of sudden cardiac death from ventricular arrhythmias escalates, especially in adolescents and young adults. As such, any young adult who presents with a history of syncope, especially during exertional activities, or an unexplained period of unconsciousness, must be queried as to any family members with similar issues, a family or personal history of hypertrophic heart disease, or any premature/unexplained death or arrhythmia in any family member.

HCM is a condition that has no sex or ethnic predilections, but 60% of patients have a known family member with similar disease. Echocardiography is the most common diagnostic modality used to suggest the diagnosis of HCM, but additional confirmation can be accomplished by septal biopsy demonstrating the typical myofibril disarray and lack of normal parallel alignment of cardiac myofibrils that is classically characteristic on histologic specimens.

Clinical manifestations of HCM tend to logically follow along the underlying degree of disease genetically expressed in each individual. Those with greater degrees of cardiac muscle fibrosis tend to have worsened diastolic dysfunction, whereby the ventricles are unable to normally relax and fill with blood during diastole. The resultant increase in left intraventricular pressure causes fluid to back up into the pulmonary system, especially during exercise or in the supine position (orthopnea). Those with greater degrees of ventricular hypertrophy and resultant left ventricular outlet obstruction will also develop the expressions of elevated diastolic filling pressures with exertional dyspnea, heart failure, and syncopal episodes due to poor cardiac output and/or ventricular arrhythmias. Ventricular arrhythmias can arise from the stretching and consequent malfunction of the electrical system of the heart from myocardial hypertrophy. The epicardial coronary arteries that must traverse the thickened myocardium and provide nourishment to the underlying cardiac musculature can also become compressed, especially during activity, when the heart is beating faster and a subsequent oxygen supply/demand mismatch evolves yielding the typical chest pain or anginal equivalent symptoms. This myocardial hypoperfusion, if not brought back into check, can also yield supraventricular and ventricular arrhythmias, myocardial ischemia, and ultimately a syncopal event.

Physical examination clues to the presence of previously undiagnosed HCM are suggested by brisk and bounding peripheral pulses and a harsh midsytolic 3-4/6 murmur heard best between the heart apex and left sternal border. The murmur can be augmented with the Valsalva maneuver and upright position, which decreases venous return to the heart and subsequent left ventricular blood volume. The literature suggests a prominent S4 is helpful in making the diagnosis by auscultation, but I am lucky if I can hear myself think during the course of my ED shift, much less hear a 4th heart sound. I surmise my prehospital colleagues would also attest to the difficulties in performing an adequate cardiac auscultatory exam in the field. EKG abnormalities suggestive of left ventricular hypertrophy (LVH) and deep septal Q waves from a hypertrophied interventricular septum are the two most common findings in HCM.

Treatment and management for a patient that has suffered a syncopal episode or an apparent sudden cardiac death event due to HCM or suspected HCM, does not deviate from any other ACLS algorithm. When the diagnosis is suspected in the pediatric age group though, serious consideration should be made to getting the patient to a tertiary care pediatric medical center with cardiology and cardiothoracic services for a higher level of evaluation and management. These patients tend to benefit the most from implanted cardioverter/defibrillators to address the underlying dysrhythmia causing the presenting complaint. With medicinal and/or surgical treatment, patients can live a normal life expectancy. Unfortunately, though, HCM is still the most common cause of sudden cardiac death on the athletic field, and tends to disproportionately afflict young adults and adolescents.

Coronary Artery Anomalies

Coronary artery anomalies are another collection of inherited conditions like HCM, that affect the course or origin of the three primary epicardial coronary arteries (right coronary artery, left anterior descending artery, left circumflex artery). The inclusion of coronary artery anomalies in this discussion is again relevant to it being one of the common etiologies of sudden cardiac death in the pediatric, adolescent, and young adult populations.

When discussing coronary artery anomalies, the dialogue should focus on the three primary epicardial arteries: right coronary artery, left anterior descending artery, and left circumflex artery. Numerous genetic variations exist for this condition, but those that afflict <1% of the population tend to be the ones focused upon in the cardiology literature. Normally the coronary arteries will arise from the proximal aorta, just distal to the aortic root outflow. The coronary arteries will then get their flow during diastole, as blood courses passively into their ostia. The most common anomaly of coronary origin is from some alternate location on the ascending aorta. Other less common positions of origin include takeoffs from a multitude of positions on the pulmonary arterial trunk or atresia of the left main coronary artery. Anomalies of coronary artery course exist when the coronary arteries deviate from their normal course following their takeoff from the aorta, then along the surface (epicardial) of the heart, and finally a dive and divide into the cardiac musculature to provide their nourishment. When the coronary arteries travel through the myocardial musculature (myocardial bridging) they can be subject to compression during the systolic phase of the cardiac cycle, similar to that noted above in the discussion on HCM. The course of the coronary arteries can also be affected by a congenital aneurysm of the artery or one that develops as a result of some acquired medical disease (i.e., syphilis, Kawasaki’s Disease). Fortunately, the presence of the more common anomalous coronary origins and courses are not associated with any other congenital abnormalities, but the rarer subtypes tend to be associated with complex heart diseases.

As with the discussion on the genetic cardiac condition, HCM, above, the clinical expression of coronary artery anomalies is directly correlated with the paucity of blood flow that the condition allows. In the most simplistic of illustrations, if oxygenated blood cannot make it to the tissues, the tissues will manifest altered behavior (i.e., direct effects of ischemia), then die. As such, when the body’s tissue oxygen demand is increased, like during exercise or other exertional activities, the expression of this anomaly becomes more pronounced. Hence, the increased prevalence of this condition in the active pediatric and adolescent populations. When the coronary arteries originate from the pulmonary trunk, the lethality of the condition may be determined by which of the three main coronary arteries has its origin at that location and the subsequent perfusion shortfall. Right coronary artery origins from the pulmonary trunk tend to have later discovery in life due to milder anginal and exertional symptoms versus the left anterior descending artery, which tends to have a more lethal and earlier expression of its presence. Nevertheless, even slight variances in the origin of the coronary arteries can have a marked impact on the timing of discovery or the lethality of the condition. Although the clinical significance of coronary aneurysms is not completely understood, when the coronary arteries abnormally course through the myocardial musculature in myocardial bridging, the arteries can be compressed during systole and yield typical anginal symptoms. During exertional activities, the ischemic oxygen supply/demand mismatch becomes even more pronounced leading to myocardial infarctions, dysrhythmias, and sudden cardiac death.

Anomalous coronary arteries must be in the differential diagnosis of any pediatric, adolescent, or young adult with an exertional syncopal episode or apparent sudden cardiac death event. While EKG is not the gold standard for diagnosis, it can be performed in the prehospital setting and may indicate indirect signs of ischemia. Although echocardiography is helpful and suggestive of the diagnosis, direct coronary angiography using CT technology or newer coronary magnetic resonance imaging are now the preferred means to noninvasively make this sometimes obscure diagnosis. The ubiquitous availability of newer generation multidetector CT scanners in the ED have fortunately made the ability to evaluate this issue much easier. As would be expected, surgery is the preferred way to address the underlying anatomic abnormalities of this condition. While surgery is being contemplated and planned for those clinically relevant variants of this disorder, exercise restriction is the mainstay of preventing the catastrophic outcomes of this ailment.

Long-QT Syndrome

Long-QT syndrome (LQTS) is another genetic malady of the heart, but one that has its predilection for the electrical system, as opposed to the structural framework (HCM, anomalous coronary arteries) of the heart. Without getting too deep into the biochemical bases of LQTS, the basic genetic defect manifests itself with an insufficient efflux of potassium out of the heart cells and/or an inappropriately elevated influx of sodium or calcium into the cardiac myocytes. This ionic imbalance yields a lengthening of the QT interval, especially during exertional or emotionally provocative scenarios. The resultant unexpected syncopal or sudden cardiac arrest often appears when the pediatric, adolescent, or young adult is in the midst of some sporting event where definitive defibrillator or pacing support is excessively delayed.

The prevalence of clinically relevant LQTS is often cited as 1:2000. The clinical manifestations of the disease may be completely silent in those who do not enjoy an active lifestyle, allowing disease detection to evade the pediatric and adolescent populations and present in the later young-adult populations. In either event, the presentation will be expressed with some sort of short or prolonged syncopal episode due to one of the ventricular tachyarrhythmias (i.e., ventricular tachycardia, torsades-de-pointes, etc.). Because seizure-like activity can accompany LQTS, and any syncopal episode that reduces blood flow to the brain, LQTS can be mistakenly overlooked as a neurological occurrence instead of a primary cardiogenic event.

The wide availability of cardiac monitors and EKGs in the prehospital setting will easily make the diagnosis for those prehospital providers who include this condition within their differential diagnosis of an unexplained syncopal event. A calculated corrected QT interval (QTc) ≥ 480 (normal < 440ms) is suggestive of the condition and may warrant further confirmatory genetic testing. A prior history of an unexplained syncopal event, a family history of sudden cardiac death, or a personal history of congenital deafness, which can accompany this condition, are further suggestive of this potentially lethal condition. First line therapy for LQTS are the beta blocker class of medicines. In particular, propranolol and nadolol are the most efficacious in this class of medications. Contrarily, commonly available metoprolol and atenolol in most EDs, tend to be minimally if not effective at all for this condition. Implantable cardioverter-defibrillator devices and Left cardiac sympathetic denervation are invasive means to manage the dysrhythmias resulting from this condition. While it is quite obvious how the cardioverter-defibrillator is protective from the arrhythmogenic manifestations of LQTS, the left cardiac sympathetic denervation procedure, which is a surgical technique to remove the first three to four thoracic ganglia, intriguingly tends to have an antifibrillatory effect by shortening the QTc interval. The threshold to implant a cardioverter-defibrillator is predicated on one or more of the following criteria: QTC > 500-550ms, prior cardiac arrest or events, patients with syncope despite maximal beta blocker therapy discussed above.

Commotio Cordis

Commotio cordis is a non-genetic, sudden death phenomenon, that only manifests itself upon an abrupt blunt impact to the anterior chest wall. This condition, which was initially described in the 18th century among industrial workers has become essentially an occurrence relegated to the athletic arenas (i.e., pitched baseball to the chest, vigorous impact during a football tackle, fall onto the chest from pole vaulting, etc.). Approximately 10-20 cases are reported to the Commotio Cordis Registry yearly, with a primary incidence (95%) in the adolescent male demography (mean age of 15). The pathophysiology of the condition is thought to be reflected in the more compliant chest wall of this younger demographic, which allows the chest wall to be suddenly compressed, possibly during an inopportune moment in the cardiac electrical cycle, and causing ventricular fibrillation, which may or may not suddenly abate. While no structural cardiac damage occurs in this condition (i.e., cardiac contusion), it has been postulated that there may be some individual susceptibility to commotio cordis, such as those with undiagnosed LQTS (see discussion above). As an aside, there may be those of you who have utilized a brisk precordial thump for those with ventricular fibrillation, that spontaneously developed in a patient in front of the healthcare provider. A review of the commotio cordis literature seems to support the utility of this procedure that is ubiquitously available to us all. It should go without saying though, that performing a precordial thump on the conscious patient subjects the provider to significant scrutiny amongst your peers, medical licensing authorities, and possibly the criminal justice system. Should a singular precordial thump not initially convert the patient affected by the commotio cordis episode, routine ACLS processes should be followed to address the presenting dysrhythmia.

Kenneth Alan Totz, DO, JD, FACEP, CLCP

No information within this report should be construed as medical or legal advice. Independent medical and/or legal advice should be sought based on each individual’s particular circumstances.

Sources

• Marian, Ali J., et al. Hypertrophic Cardiomyopathy Genetics, Pathogenesis, Clinical Manifestations, Diagnosis, and Therapy. Clinical Research. September 15, 2017.
• Gentile, Francesco, et al. Coronary Artery Anomalies. Circulation. 2021; 144:983-996.
• Schwartz, Peter J, et al. Long-QT Syndrome From Genetics to Management. Circ Arrhythm Electrophysiol. August 2012.
• Link, Mark S. Commotio Cordis. Circ Arrhythm Electrophysiol. April 2012.