Risk Factors of Sudden Cardiac Death
Potential risk factors for SCD that have been analyzed include a family history of SCD, race, gender, or a lack of screening. Although physical exertion increases risk, death rates from athletes are similar to the general population for sudden death, and some student-athlete SCDs did not occur during physical activity.6 Race and gender suggest some minor changes in risk stratification. Blacks are slightly more at risk than Whites in various epidemiological studies.1,10-13 Epidemiological research has suggested that males are at greater risk than females.8 However, the rate of sports participation is greater in males compared to females, making an unstratified sample difficult in comparison.
Other risk factors for cardiac conditions include history of syncope, or unexplained collapse, and family history. A difficulty with cardiac conditions is that the initial presentation includes seizurelike activity and unconsciousness. This increases diagnostic difficulty if there was no family or personal history of collapse because some clinicians may assume it was a seizure, and a detailed history is not possible if the patient is unconscious. At a minimum, asking questions related to these factors as part of the preparticipation evaluation is an effective screening process.8-13
Cardiac Screening for Prevention of Sudden Cardiac Death
Health care professionals must strive, at 2 distinct times, to limit the potential of death from a sudden cardiac condition. First, the preparticipation evaluation should serve as an efficient and thorough risk screening. Second, once an episode occurs, a simple and effective EAP must be in place.8 Many strategies and recommendations for practice exist regarding the prevention of SCD. Because most death occurs as a result of structural abnormality, imaging via echocardiogram is considered by many as a gold standard in preseason screening.14-16 This is effective in diagnosing many with HCM, but true sensitivity and specificity have yet to be determined for all causes.9 The price of individual testing via echocardiogram makes it unattainable for many.15 Other screening strategies include preseason resting electrocardiogram (EKG) analysis and review as part of the process.8,9,11,12 Although effective, this assessment is somewhat subjective according to the practitioner and is based on electrical activity. Electrical and structural dysfunction in the heart are sometimes unrelated, which complicates specific recommendations. Some athletes gain ventricular thickness secondary to normal adaptation to intense training, known as athletic heart. Those with athletic heart are not at risk of SCD but can sometimes be diagnosed with HCM and be excluded from participation needlessly. Proponents of echocardiogram screening advocate in favor of disqualifying too many because they are saving lives for some with HCM.17 More evidence regarding the effectiveness of electrocardiogram in preparticipation screenings is discussed in Chapter 11.
It is widely accepted that preseason screening for cardiac pathology is important in preventing SCD.8 However, a consensus regarding best practice for screening has yet to be established. The American Heart Association (AHA) history questions are standard, but because symptoms are often not present until a major episode, their effectiveness is limited.16 The effect of implementing a rigorous and mandatory screening protocol in the Veneto region of Italy resulted in a drastic incidence decrease from 4.19 to 0.21/100,000 athletes.18 Standard EKGs and exercise restrictions have reduced incidence but may limit participation for those without contraindication to exercise.15 A lack of consistency in interpretation of resting EKG analysis has also compromised the efficiency of a more cost-effective screening method.19 Drezner et al9 attempted to limit inconsistency with a template of step-by-step interpretation for physicians. Recommendations supported to date include a minimum of the 12-question AHA questionnaire, auscultation, and physical examination.8,11,12,16 Further screening that is recommended is routine EKG read by a trained physician.8,9 Follow-up echocardiogram is supported only when other methods suggest pathology or when resources are provided at a minimum cost.7,15,18 In a recent study, history and physical examination identified 40% of potentially fatal conditions, and EKG was deemed appropriate in confirming or identifying more pathologies.17 At a minimum, anyone participating in organized athletics should receive basic screening, including the cardiac screening questionnaire from the AHA,16 blood pressure, pulse, and auscultation as part of his or her physical examination.8,11,12,15
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Emergency Planning for Sudden Cardiac Death
The second potential for saving lives from cardiac pathology occurs once a patient collapses. If a cardiac episode presents, timing is key. EAPs that have been reviewed and practiced lead to better outcomes.8,11,12,19 Three actions that save lives in these instances include early emergency medical services activation, cardiopulmonary resuscitation, and automated external defibrillator application.8,11,12,19 The rate of survival decreases 10% for every minute of delay in treatment in cardiac arrest. Education and training for athletes, coaches, and strength staff can help expedite recognition and implementation of life-saving techniques.8,11,12 Recent incidence data on SCD suggest that current practices have been successful at decreasing the number of deaths. In a study based in Minnesota, SCD was infrequent, and a prompt EAP was responsible for saving 33% of potentially fatal episodes.11 Another study demonstrated 85% effectiveness for high school athletes and 61% survival in others given quick access to automated external defibrillators housed in high schools.12 However, most instances were not a result of sport participation but involved bystanders (coaches, teachers, and fans).11,12,19 Experts agree on consistent recommendations regarding expedited recognition and treatment for cardiac episodes. Although limited evidence is available to support these recommendations, sports medicine professionals do not disagree with these standards. Large cohort studies are underway to demonstrate the best prevention methods for SCD.
Exertional sickling occurs when muscle cells are deprived of oxygen during physical activity because the red blood cells of the athlete are deformed. Athletes at risk of exertional sickling are carriers of sickle cell trait. It is an inherited condition found predominantly in Black, Hispanic, and Mediterranean populations.20 When intense or long-term exercise ensues, sickle cell trait causes red blood cells to take on an abnormal sickle shape (Figure 7-1). When this occurs, logjams or blood clots can occur in the blood vessels, depriving cells of oxygen or nutrients. Ultimately, rhabdomyolysis occurs due to muscle breakdown, which stresses the kidneys, heart, and blood vessels.8,20 If not corrected, renal failure, hyperkalemia, myocardial infarction, stroke, and pulmonary edema are possible and often fatal. Athletic trainers must quickly recognize the signs and symptoms of exertional sickling and apply life-saving treatment promptly to prevent