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Sudden Cardiac Death in Young Military Recruits: Guarding the Heart of a Soldier

Posted on: Friday, 10 December 2004, 03:00 CST

Sudden unexpected death is always tragic, but especially so when it occurs in soldiers. Death in combat is devastating, but it is an inherent risk of an occupation that calls for individuals to put their life at risk for others. Sudden cardiac death during basic military training should raise concern because it implies failures at many levels: a potentially fatal cardiovascular abnormality that fails to generate symptoms or signs of the underlying disorder; the patient's failure to recognize and report unusual symptoms; the physician's failure to recognize nonspecific symptoms that may represent a serious underlying cardiovascular condition; routine screening methods that fail to detect obscure cardiovascular abnormalities; and, finally, resuscitation efforts that fail to restore spontaneous circulation. However, most of these "failures" do not invoke blame; rather, they present a challenge to the medical and scientific community to prolong life by reducing the occurrence of sudden unexpected death.

In this issue, Eckart and colleagues (1) take another step toward a better understanding of sudden death by providing more evidence that certain cardiovascular conditions account for most sudden deaths in military recruits. The identification of these conditions raises the possibility that their subsequent improved detection could reduce the incidence of sudden cardiac death. This retrospective cohort study included 6.3 million U.S. military recruits over a 25-year period (1977-2001). All recruits, who were enlisted m all branches of military service, underwent a preenlistment screening evaluation that consisted of a personal history and physical examination. Each death that occurred at a military site before the completion of initial training led to a thorough investigation and an autopsy. Of those who died, 90% were men, and the median age was 19 years. The authors defined sudden death as death that occurred within 1 hour of the incident event. Of 126 nontraumatic sudden deaths (13/100000 recruit-years), 108 (86%) were exercise-related. Despite thorough investigation, a large proportion (35%) of sudden deaths were unexplained.

Sixty-four of the deceased (51%) had an identifiable cardiac abnormality. The most common cardiac condition, which accounted for 33% of identified cardiac abnormalities and 16% of deaths, was an anomalous coronary artery, in which the left coronary artery originates at the right anterior sinus of Valsalva and courses between the aorta and pulmonary artery to reach the left ventricle. Myocarditis accounted for 20% of cardiac abnormalities and 10% of deaths, and hypertrophic cardiomyopathy represented 12% of cardiac abnormalities and 6% of deaths. Premortem symptoms (for example, syncope, chest pain, dyspnea, and palpitations) were reported significantly more frequently in recruits with cardiac abnormalities than in deceased recruits with no identified cause of death. However, the occurrence of such symptoms in the entire cohort of recruits is not known; therefore, it is not possible to measure specificity of these findings as predictors of sudden death.

The findings reported by Eckart and colleagues (1) are unique because they focus on the causes of sudden nontraumatic death in military recruits. Their study, when considered along with other reports that more broadly describe the causes of nontraumatic death in the military (2-6) (Table), suggest several conclusions: nontraumatic death is rare; most nontraumatic deaths among the military are exercise-related; cardiovascular abnormalities account for many nontraumatic deaths in the military; and the most common cardiovascular conditions are anomalous coronary arteries, hypertrophic cardiomyopathy, and myocarditis among military personnel younger than 30 years of age and atherosclerotic coronary disease among those older than 30 years of age. Taken together, these findings are remarkably similar to those found in reports that define the incidence and causes of sudden death during exercise in the nonmilitary population-specifically, young athletes in the United States (7, 8).

The estimated incidence of sudden death in high school and college athletes is 1/133 333 men and 1/769 230 women. In both young and older persons, sudden death related to exercise is more common in men (8). Despite the low absolute risk for sudden cardiac death during exercise, the rate of sudden death is considerably greater during exercise than at rest (9, 10). The risk for sudden death during exercise in young persons is much lower than among middle- aged adults (6 to 7/100 000 exercisers per year) because so few young persons have advanced coronary artery disease and because congenital and genetic cardiovascular problems (for example, hypertrophic cardiomyopathy, anomalous coronary arteries, congenital long QT syndrome) are so rare. The estimated prevalence of these conditions in the young athletic population is 0.2% (11), which is probably similar to the prevalence in young military recruits. Among young athletes, hypertrophie cardiomyopathy and congenital coronary artery anomalies are the most common conditions associated with sudden cardiac death (7). Emotional stress, myocardial ischemia, sympatheto-vagal imbalance, and hemodynamic changes that occur during exercise in the presence of these conditions probably trigger life-threatening ventricular arrhythmias and sudden death (7).

Hypertrophic cardiomyopathy may be difficult to detect; the nonobstructive form is most common, and the physical examination is therefore generally unrevealine. Most persons with this condition are asymptomatic, and many have no family history of premature sudden cardiac death (11). The most common coronary anomalies associated with sudden death and exercise-related death are the left main coronary artery originating from the right coronary sinus, the right coronary artery originating from the left coronary sinus, and either artery coursing between the pulmonary artery and aorta (12). With exercise, the pulmonary artery and the aorta dilate and compress the already narrowed ostium. Symptoms, when they do occur, include syncope and exertional angina. Without overt symptoms, these anomalies are difficult to identify, although affected patients may present with resting electrocardiographic abnormalities (13).

Table. Nontraumatic Deaths in the Military Services*

The medical screening conducted at a Military Entrance Processing Station consists of a personal medical history and a physical examination with cardiac auscultation. Electrocardiography is performed only if abnormalities are identified. Although several cardiovascular diagnoses are sufficient cause to disqualify someone from military service, many cardiovascular conditions are clinically silent and would escape detection by the current screening program. These diagnoses include abnormalities in the conduction system, myocardial diseases, atherosclerotic coronary disease, and many congenital or genetic heart diseases. Since no screening test or procedure will yield 100% sensitivity and specificity or guarantee a zerorisk outcome, what can be done to further improve detection? The American Heart Association does not recommend routine electrocardiography or echocardiography in the initial screening evaluation of young athletes because of the poor diagnostic accuracy and high aggregate cost in this low-risk population (7). Accordingly, in view of the very low incidence of sudden cardiac death in military recruits, routine noninvasive testing is not warranted until better, more accurate, and lower-cost testing methods for highrisk cardiac conditions are available.

While waiting for improved screening tests, what can we do to minimize the number of military recruits who die suddenly? I suggest that the military entrance evaluation include the following measures. First, teach those responsible for medical evaluations and supervision of recruits about the most common causes of sudden death in recruits so that they are alert to signs and symptoms of cardiac conditions during a routine medical history or at any time during recruit training. Second, include in the initial medical history questions about chest discomfort (particularly during exertion); syncope or presyncope; excessive or newonset dyspnea during exercise; and a family history of premature or sudden death, hypertrophie cardiomyopathy, and inherited (genetic) cardiovascular diseases. Third, assess global cardiovascular risk by using the Framingham Risk Score (14), particularly in persons 30 years of age and older; in persons who are at intermediate or high 10-year risk for coronary heart disease, further assessment with resting electrocardiography and exercise stress testing should be considered (15). Fourth, include in the basic physical examination a careful assessment for abnormal heart rate and rhythm, elevated jugular venous pressure, vascular bruits, abnormal heart size, and abnormal heart sounds; these findings should prompt further cardiovascular testing. Finally, report a recruit who develops chest discomfort, syncope or presyncope, or excessive dyspnea during basic training to medical personnel for an appropriate evaluation.

References

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2. Drehner D, Neuhauser KM, NeuKauser TS, Blackwood GV. Death among U.S. Air Force basic trainees, 1956 to 1996. Mil Med. 1999; 164:841-7. [PMID: 10628154]

3. Gardner JW, Gutmann PD, Potter RN, Kark JA. Nontraumatic exerciserelated deaths in the U.S. military, 1996-1999. Mil Med. 2002;167:964-70. [PMIO: 12502168]

4. Phillips M, Robinowit/ M, Higgins JR, Bonn KJ, Reed T, Virmani R. Sudden cardiac death in Air Force recruits. A 20-year review. JAMA. 1986;256: 2696-9. [PMID: 3773175]

5. Scoville SL, Gardner JW, Magill AJ, Potter RN, Kark JA. Nontraumatic deaths during U.S. Armed Forces basic training, 1977- 2001. Am J Prcv Med. 20(M;26:205-12. [PMlH: 15026099]

6. Amital H, Glikson M, Burstein M, AfeU A, Sinnreich R, Web Y, et al. Clinical characteristics of unexpected death among young enlisted military personnel: results of a three-decade retrospective surveillance. Chest. 2004;I26:52833. [PMlD: 15302740]

7. Maron BJ, Chaitman BR, Ackerman MJ, Bayes de Luna A, Corrado D, Cross-on JE, et al. Recommendations tor physical activity and recreational sports participation For young patients with genetic cardiovascular diseases. Circulation. 2004:109:2807-16. [PMID: 15184297]

8. Van Camp SP, Bloor CM, Mueller PO, Cantu RC, Olson HG. Nontraumatic sports death in high school and college athletes. Mcd Sci Sports F.xerc. 199-5:27:641-7. [PMlD: 76748671

9. Thompson PD, Funk EJ, Carleton RA, Stumer WQ. incidence of death during jogging in Rhode Island from 1975 through 1980. JAMA. 1982;247: 2535-8. [PMID: 6978411]

10. Siscovick DS, Weiss NS, Fletchcr RH, Lasky T. The incidence of primary cardiac arrest during vigorous exercise. N Engl J Med. 1984;311:874-7. [PMID: 6472399]

11. Maron BJ, Thompson PD, Puffer JC, McGrew CA, Strong WB, Douglas PS, et al. Cardiovascular preparticipation screening of competitive athletes. A statement for health professionals from the Sudden Death Committee (clinical cardiology) and Congenital Cardiac Defects Committee (cardiovascular disease in the young), American Heart Association. Circulation. 1996;94:850-6. [PMID: 87727111

12. Taylor AJ, Rogan KM, Virmani R. Sudden cardiac death associated with isolated congenital coronary artery anomalies. J Am Coll Curdiol. 1992;20:640-7. [PMID: 1512344]

13. Barth CW 3rd, Roberts WC. Left main coronary artery originating from the right sinus of Valsalva and coursing between the aorta and pulmonary trunk. J Am Coll Cardiol. 1986:7:366-73. [PMID: 3944356]

14. Wilson PW, D'Agostino RB, Levy D, Belanger AM, Silbershatz H, Kannel WB. Prediction of coronary heart disease using risk factor categories. Circulation. 1998:97:1837-47. [PMID: 9603539]

15. Balady GJ, Larson MG, Vasan RS, Leip EP, O'Donnell CJ, Levy D. Usefulness of exercise testing in the prediction of coronary disease risk among asymptomatic persons as a function of the Framingham risk score. Circulation. 2004:110:1920-5. [PMID: 15451778]

2004 American College of Physicians

Gary J. Balady, MD

Boston University School of Medicine

Boston, MA 02118

Potential Financial Conflicts of Interest: None disclosed.

Requests for Single Reprints: Gary J. Balady, MD, section of Cardiology, Boston Medical Center, 88 East Newton Street, Boston, MA 02118; e-mail, gary.balady@bmc.org.

Ann Intern Med. 2004;141:882-884.

Copyright American College of Physicians Dec 7, 2004

Source: Annals of Internal Medicine

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