Sudden cardiac death in children and adolescents.
Sudden cardiac death in children and adolescents is rare but seems to be more frequent than previously reported. The occurrence of such an event is very devastating. Primary caretakers should be aware of the etiologies and the importance of screening. This article will discuss etiologies of sudden cardiac death in children and adolescents and will describe strategies for education and prevention.
Keywords: sudden cardiac death, CPR, automatic external defibrillators, Project Adam
Sudden cardiac death (SCD) in the pediatric and adolescent population is an uncommon event. Within our community we have had seven episodes of sudden cardiac death in high school student-athletes in the last 18 months. Only one of those students survived. These episodes, along with the deaths of some high-profile athletes over the last several years, have raised the anxiety levels of physicians, parents, and teachers, as well as students themselves. This article will review the risks and etiologies of SCD in children and adolescents and will offer an opinion with regard to prevention.
It is estimated that the risk of SCD in children and adolescents is 1 in 200,000 to 400,000. Data suggests that an estimated 5 million athletes compete at the high school level. Therefore, although the incidence of SCD in children and adolescents is much less than in adults (300,000 to 400,000 episodes of SCD in adults annually), it is not a minor problem.
SCD in children and adolescents has been reported during many different competitive athletic events. However a review of the literature has suggested that the events with the greatest frequency were basketball and football, the former the most common. Though the reason for this is not exactly clear, one can speculate that it may be related to the high intensity of the sport.
Causes of Sudden Cardiac Death in the Pediatric and Adolescent Population
The predominant cause of SCD in adults is atherosclerotic coronary artery disease. This etiology is virtually unheard of in children and adolescents. The causes in children are much more diverse and are usually congenital. With rare exception (see Table I), a child or adolescent with a normal heart'' is not at risk for SCD. A possible classification of the etiologies of SCD in children or adolescents is also offered in Table I.
This table offers one of many possible classification schemes. The clinical relevance of the above is that apparent congenital heart disease identifies a subset of patients at highest risk for SCD. Pediatric cardiologists typically follow these patients with surgically corrected or palliated congenital heart disease closely. Unfortunately, in the population at large, there is another subset of patients in whom structural heart disease is recognized only after a fatal or an aborted episode of SCD occurs. It is this group of patients that we will focus on in the remainder of this article. Therefore, there is this subset of patients who are asymptomatic yet have potentially life-threatening cardiac disease and are unknown to us. In order to prevent SCD in this group of patients, several issues should be raised:
What is our method for screening these patients? Is the routine pre-participation sports physical adequate? How can it be optimized? Is routine screening of all high school athletes with ECG and echocardiography reasonable? Will it be effective? If screening cannot identify all children and adolescents at risk, are there other ways that SCD may be prevented?
Identification of Patients at Risk for Sudden Cardiac Death
Survival rates in children and adolescents after sudden cardiac death is extremely poor. Therefore, it is a very big challenge to identify, prospectively, those children and adolescents, ostensibly healthy and asymptomatic, who have cardiac abnormalities that place them at risk for SCD. In many of these patients ventricular arrhythmias and SCD may be the only manifestation of heart disease. The difficulty in identifying these patients is obvious and is very challenging.
Current screening techniques are not able to identify all children and adolescents at risk of SCD. However, it is essential that screening be very thorough. The current screening involves thorough history, family history, and physical examination.
Although the majority of the children and adolescents at risk are asymptomatic, some do have symptoms that may be subtle, or that are denied. Palpitations, chest pain or syncope, especially with exertion, are symptoms that are concerning. In addition, a careful family history is essential. A known family history of hypertrophic cardiomyopathy, LQTS, cardiomyopathy or ARVD warrants further work-up. In addition, a family history of SCD at a young age in other family members may be important. Some schools and pediatricians have developed a pre-participation checklist for student athletes. This checklist will ask all relevant questions with regard to history and family history, and may uncover a symptom in the past, or a family member's death, that might warrant further investigation. Finally, a careful physical examination may uncover a heart murmur or an irregular heart beat. Usually, however, the physical examination is entirely normal in this population of children and adolescents.
Should high school athletes he routinely screened with EGG and echocardiography? It has been estimated that this approach would cost $250,O00-$500,000 per each case detected. For an individual case it does not seem appropriate to argue against universal screening from a cost-benefit perspective. However, is it appropriate to argue against screening from a healthcare allocation standpoint? The answer is not clear and is certainly controversial. However, we do believe that, even with universal screening of high school athletes with EGG and echocardiography, there will be many children and adolescents that will still not be detected. Some of the cardiac abnormalities that place children and adolescents at risk are very difficult to image, such as a coronary artery abnormality. It would be unlikely that these could be detected by mass screening.
Further Discussion of Some of the Specific Causes of SCD in Children and Adolescents
Hypertrophic cardiomyopathy (HCM) is the most frequent cause of sudden cardiac death in undiagnosed student athletes. It is more common than previously recognized with a prevalence of 1 in 500 in the U.S. population. It is thought to be the result of mutations in any one of four components of the cardiac sarcomere.
SCD is a well-known complication of hypertrophic cardiomyopathy. The literature suggests an annual incidence of SCD of 0.6% but may be as high as 1%. HCM may be difficult to identify in that the physical examination is typically normal. A careful family history may provide the best clue, because HCM can be familial. A history of early and/or unexplained SCD in other family members or a known history of HCM is important. Factors that increase the risk of SCD in patients with HCM include a family history of HCM with SCD, clinical symptoms, and a history of ventricular arrhythmias.
Once identified, the patient with HCM can undergo treatment. The medical and/or surgical treatment of HCM and its role in the prevention of SCD is beyond the scope of this report.
Congenital Coronary Artery Abnormalities
SCD may be the presenting symptom in patients with undiagnosed coronary artery abnormalities, and may be discovered only at the time of autopsy. Some patients may develop symptoms of chest pain and or syncope with exertion with documented ischemia. Generally, the ischemia is caused by either an abnormal coronary artery origin, an intramural course of the coronary artery within the aorta, compression of the coronary artery between the aorta and the pulmonary artery, and/or origin of the coronary artery from the pulmonary artery. In any case, the resultant coronary ischemia may be life-threatening. The potential coronary artery abnormalities that may be associated with SCD include:
* Left main coronary artery arising from the right sinus of Valsalva
* Coronary ostial stenosis (may be associated with aortic stenosis)
* Single coronary ostia
* Right coronary artery from the left sinus of Valsalva
* Anomalous origin of the left coronary artery form the pulmonary artery
If the congenital coronary artery can be diagnosed, surgical intervention may correct or palliate the lesion and either prevent or minimize the risk of SCD.
Long QT Syndrome (LQTS)
Patients with congenital or acquired LQTS can present with SCD. Congenital LQTS is hereditary with a dominant mode of inheritance. The heterozygous form is most common and is called Romano-Ward Syndrome. The Jervell-Lange-Nielsen Syndrome is more severe, is the rarer homozygous form, and is associated with congenital deafness. A corrected QT interval of greater than 0.44 seconds is considered to be abnormal; however SCD seems to be a risk when the corrected QT interval is markedly prolonged, in the range of 0.50 seconds or more. The prolongation of the QT interval can trigger life-threatening ventricular arrlrythmias, including Torsades de Pointes and ventricular fibrillation.
SCD may be the presenting symptom of LQTS. An early family history of SCD, syncope, unusual seizure, drops attacks or congenital deafness should alert the caretaker to the possibility of LQTS. Once diagnosed, treatment may include beta-blockers, mexilitene, stellate ganglionectomy, pacemaker therapy, implantable defibrillator, or combinations of the above. Treatment is thought to reduce but not eliminate the risk of SCD.
Wolf-Parkins on-White Syndrome (WPW)
The incidence of WPW in children and adolescents is 0.1%. WPW can be associated with SCD. For SCD to occur in patients with WPW, a rapidly-conducting accessory pathway plus atrial fibrillation are necessary. This manifests as an irregularly, irregular wide QRS tachycardla, and is a life-threatening arrhythmia. SCD can occur as this combination can result in ventricular fibrillation. It is rare for this combination to occur in children under the age of eight years old. The treatment of choice is intravenous procainamide or synchronized DC cardioversion. Patients with this rhythm should undergo electrophysiologic testing and radiofrequency ablation of the accessory pathway. This will eliminate the risk of SCD in patients with WPW.
Commotio cordis has only recently been described. A blunt blow to the chest with resultant ventricular tachycardia or fibrillation causes it. It has been described in baseball players and hockey players. It is postulated that in order for a life threatening arrhythmia to occur, the blunt trauma must come during "the electrically vulnerable" period of the cardiac cycle. Although extremely rare, this potential entity has caused some to advocate for the use of chest protectors for young athletes in the sports that place them at highest risk.
Intervention for Children and Adolescents Who Present with SCD. How We Can Stack the Deck in Our Favor
The screening methods, no matter how good they are, will not allow for detection of every case that places the child or adolescent at risk for SCD. It is our contention that education and early intervention will save the lives of many of the children and adolescents that present with SCD. Pooled adult cardiac arrest studies suggest that the outcome for patients with documented ventricular fibrillation is improved with early and rapid defibrillation. Studies suggest that there is a 10% increase in mortality for every minute of delay of defibrillation in the patient who has had SCD from ventricular fibrillation. There is considerable controversy with regard to the frequency of ventricular fibrillation in children and adolescents who present with SCD. Many studies suggest that children and adolescents have a much lower incidence of ventricular fibrillation than adults. However it is agreed that the studies undoubtedly underestimate the true incidence of ventricular fibrillation in the younger subgroup.
It is our contention that early deployment of CPR and rapid defibrillation will save the lives of some of the children and adolescents who experience SCD. We have undertaken an educational/deployment project, Project Adam, within the high schools in the state of Wisconsin. It is our goal to explore the feasibility of teaching CPR to all high school students before graduation. It is also a goal to place automatic external defibrillators in all high schools and at all high school athletic events; and to train a group of teachers, coaches, trainers, custodial staff, parents and students in their use. Public access defibrillation has been popularized over the last several years and the early information suggests that this is a useful treatment modality in the adult population. We are currently assessing a cost-effectiveness model of such an approach in the high school setting.
References upon request.
Table 1 Patients with known, previously recognized heart disease Congenital Tetralogy of Fallot Transposition of the great arteries (Mustard or Senning operation) S/P Fontan operation Aortic stenosis Marfan syndrome Eisenmenger syndrome Congenital heart block Postoperative heart block Acquired Kawasaki syndrome Dilated cardiomyopathy Myocarditis Patients with previously unrecognized, undiagnosed heart disease With structural heart disease Hypertrophic cardiomyopathy Congenital cardiac abnormalities Arrhythmogenic right ventricular dysplasia Without structural heart disease Long QT syndrome Wolf-Parkinson-White syndrome Primary ventricular tachycardia and ventricular fibrillation Primary pulmonary hypertension Patients without an underlying cardiac condition Commotio cordis Drug abuse (cocaine and other stimulants)