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InFocus: CV Diseases Most Common Cause of Sudden Death in Young, but Few Have Symptoms to Predict Risk

Roberts, James R. MD

doi: 10.1097/01.EEM.0000512771.08130.7c
InFocus

Dr. Robertsis a professor of emergency medicine and toxicology at the Drexel University College of Medicine in Philadelphia. Read the Procedural Pause, a blog by Dr. Roberts and his daughter, Martha Roberts, ACNP, CEN, athttp://bit.ly/EMN-ProceduralPause, and read his past columns athttp://bit.ly/EMN-InFocus.

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Sudden death among children and young adults is an unexpected and always devastating event for family and friends. A young individual who comes to the ED in cardiac arrest is stressful all clinicians, paramedics, and even other patients. Many young victims of cardiac arrest had no prior discernible medical problems, seemed perfectly healthy, and died suddenly for no apparent reason.

A common cause of sudden death these days of a young person is drug overdose, but one must be careful in assuming that etiology without further information. It's probably best not to speculate on a cause of death when a previously healthy young person dies in your ED of nontraumatic reasons and with a medical history that is without apparent clinical clues.

The epidemiology and clinical or pathophysiologic characteristics of young individuals who die suddenly is poorly defined. Unlike older individuals who die of sudden death primarily from coronary artery disease, those between the ages of 1 and 35 suffer cardiac arrest primarily from structural heart disease and arrhythmogenic disorders. The cause of death, though, even after in-depth investigations, remains unexplained in about 10-20 percent of such cases.

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A Prospective Study of Sudden Cardiac Death among Children and Young Adults

Bagnell RD, et al.

N Engl J Med

2016;374(25):2441

The authors of this study of almost 500 sudden deaths in young people in Australia and New Zealand prospectively collected clinical, demographic, and autopsy information on all causes of sudden death in those ages 1 to 35 over a two-year period. At least 59 genes were analyzed for clinically relevant gene mutations.

Previous studies have demonstrated about 0.5 to two deaths per 100,000 patient years in young people. About a quarter of the cases of sudden cardiac death among children and young adults have remained unexplained even after extensive evaluation that includes toxicology analysis and histologic studies. Generally, a sudden cardiac death in such cases has been attributed to epilepsy, Brugada syndrome, a prolonged QT syndrome, or catecholamine-induced polymorphic ventricular tachycardia in the absence of drug- or trauma-related deaths. These conditions will not be diagnosed at autopsy. Other causes include aortic dissection, intracranial hemorrhage, myocarditis, pulmonary embolism, and asthma, but these are usually readily evident at autopsy. A genetic cause of death has been postulated in about a third of individuals subject to postmortem genetic testing, but genetic studies are rarely performed at autopsy.

Table Ca

Table Ca

This extensive study involved comprehensive autopsy examination and genetic testing in individuals from ages 1 to 35 who suffered sudden cardiac arrest. It included data from all major forensic pathology centers in Australia and New Zealand. Unexplained sudden cardiac death was defined as death for which no cause was identified after a complete and comprehensive autopsy examination that included histologic and toxicologic studies. Sophisticated analysis of DNA was performed on 51 of 113 cases. Overall, 59 cardiac genes related to arrhythmias and cardiomyopathy were analyzed.

A total of 198 (40%) of the 490 cases of sudden cardiac death remained unexplained on initial evaluation. DNA testing was available on 113 patients. Seventy-two percent of the patients were male with a mean age of 24 +/- 10 years, with the greatest number of cases occurring in those 31 to 35. A structurally normal heart was found in about half of the cases. Coronary artery disease was found in 24 percent, a variety of cardiomyopathies were found in 16 percent of cases, myocarditis occurred in seven percent of cases, and aortic dissection was seen in four percent. The vast majority of cases (65%) occurred while the individual was sleeping or at rest. Only 15 percent of cases of sudden death occurred during or proximal to exercise.

Overall, a clinically relevant cardiac gene mutation was identified in 27 percent of unexplained sudden cardiac death in which genetic testing was performed. The authors said adding genetic testing to autopsy would substantially increase the identification of the probable cause of sudden cardiac death among children and young adults. The most common explained causes of sudden cardiac death were coronary artery disease (24%) and inherited cardiomyopathies (16%). No specific cause of death was ultimately identified in about 30 percent of cases. Thirteen percent of the families that could be studied had inherited arrhythmogenic disease or inherited cardiomyopathy.

The authors were unable to explain why the majority of sudden deaths occurred when a person was sleeping or at rest as opposed to during activity or exercise. Apparently, patients were not included in the analysis if a toxicology cause was expected.

Comment: Nontraumatic death in young patients is well known to emergency clinicians, yet it remains a memorable event. Other investigators have also concluded that the main cause of sudden death in teenagers and young adults is due to cardiovascular conditions. Van Camp, et al., reported on 126 high school athletes and 34 college athletes who suffered a nontraumatic death. (Med Sci Sports Exerc 1995;27[5]:641) As with most studies, male athletes predominated. They found that hypertrophic cardiomyopathy and congenital coronary abnormalities were the most common cause of death in these athletes. A more recent study by Harmon, et al., found that cardiovascular-related sudden death was the leading cause of death, with 75 percent of sudden death occurring during exertion. (Circulation 2011;123[15]:1594.) The incidence of sudden cardiac death was one in 43, or 770 participants per year, in an analysis of NCAA-related deaths.

Attempting to identify children and young adults prospectively who are at risk for sudden cardiac arrest, Drezner, et al., (J Am Board Fam Med 2012;25[4]:408) investigated warning symptoms and family history of cardiovascular disease gleaned from questionnaires of families whose child or young adult suffered sudden cardiac arrest. The average age at death was 16, predominantly white men, in the 87 families that completed this study. About three-quarters of sudden cardiac arrest victims were reported by the parents to have had at least one cardiovascular symptom before their fatal event. These symptoms included a rather nonspecific complaint of fatigue (44%) and near syncope or lightheadedness (30%).

It is unlikely that an otherwise healthy individual would have a cardiac workup with only these symptoms. Interestingly, 24 percent of sudden cardiac arrest victims had one or more episodes of syncope or unexplained seizure that was not diagnosed as a cardiac disorder before the sudden death. These symptoms occurred on average 30 months before sudden cardiac arrest, but the symptom was brought to the attention of a child's physician in only 41 percent of the cases.

Syncope can be a benign event or a tipoff to a future sudden death. Most emergency clinicians are not very excited about evaluating a young individual who has had a syncopal event for no reason. After a normal physical exam, a negative past medical history, and normal basic testing, it's almost impossible to get these patients admitted to the hospital for observation or further workup. A vasovagal episode is usually diagnosed.

Three diagnosable cardiac conditions can cause syncope prior to sudden death: Wolff-Parkinson-White syndrome, long QT interval, and Brugada syndrome. An ECG in the ED specifically looking for these abnormalities is axiomatic for any age group with syncope.

Many seizure disorders are cardiac in nature from a fleeting arrhythmia, but again, that process is difficult to diagnose in the ED. Most patients with a seizure are usually referred to a neurologist, not a cardiologist, if they are not admitted.

The ED approach to otherwise healthy individuals with syncopal events varies greatly among clinicians. One rarely finds a cause through history, physical exam, or basic laboratory or ECG testing. Hospital discharge is usually the outcome when all these return as normal. Few clinicians would discharge an 80-year-old who had an obvious syncopal event with normal findings, but the incidence of serious causes of syncope in young people paints a different picture.

A family history certainly should be taken in as much detail as possible, the ECG checked and rechecked for subtle abnormalities, and a certain period of ECG monitoring done for the young patient with syncope. Most of us have been taught that syncope during exercise is a tipoff to heart disease, but most patients died suddenly while resting or asleep. The first episode of syncope is rarely followed by sudden death in a few hours, so an outpatient workup is suggested. I would generally do an echocardiogram while the young patient is still in the ED because structural cardiac abnormalities and sudden cardiac arrest are a common cause of syncope, but I must say that my positive rate has been quite low. Picking up a hypertrophic cardiomyopathy in an athletic adolescent may just save his life.

Routine screening of children for potential causes of sudden cardiac arrest is controversial. It is clearly not cost-effective to perform a routine ECG on all pediatric patients. The American Heart Association and the American Academy of Pediatrics state that the most cost-effective initial screening for children and adolescents for cardiac disease is a detailed history and physical examination alone, and an ECG is not recommended as an initial screening test. Even for competitive athletes, a history and physical examination alone are currently recommended to screen for potential sudden cardiac death.

Cardiovascular diseases remain the most common causes of sudden unexpected death in young patients. Unfortunately, many of those with sudden death have few or nonspecific prodromal symptoms to identify those at risk. Although not available at many centers, a molecular autopsy for postmortem genetic testing for channelopathies and cardiomyopathies may become more common.

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Genetic Cardiac Diseases Associated with Sudden Cardiac Death

  • Cardiomyopathies (hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, dilated cardiomyopathy, and restrictive cardiomyopathy)
  • Ion channelopathies resulting in conduction defects (congenital long QT syndrome, Brugada syndrome, short QT syndrome, and catecholaminergic polymorphic ventricular tachycardia)
  • Familial Wolff-Parkinson-White syndrome
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Causes of Sudden Cardiac Arrest in Children and Young Adults

  • Coronary artery disease (29%)
  • Primary arrhythmia electrical conduction defects (22%), including long QT and Wolff-Parkinson-White syndrome
  • Cardiomyopathy (20%), including hypertrophic cardiomyopathy, dilated cardiomyopathy, and myocarditis
  • Congenital cardiac disease (15%), such as tetralogy of Fallot, hypoplastic left heart syndrome, and transposition of the great arteries
  • Other cardiac disorders (8%), including coronary arteritis, anomalous origin of coronary arteries, aortic dissection, and mitral valve prolapse
  • Unspecified cardiac disease (7%)

Source: Circulation 2012;126(11):1363.

Reader Feedback: Readers are invited to ask specific questions and offer personal experiences, comments, or observations on InFocus topics. Literature references are appreciated. Pertinent responses will be published in a future issue. Please send comments to emn@lww.com.

Dr. Roberts: In response to your article, “Managing Opioid Overdose in a New World” (EMN 2016;38[12]:9; http://bit.ly/InFocusDec16), I wanted to note that many health districts in Ontario, Canada, are still teaching laypersons chest compressions only for opioid overdose. Laypersons are misdiagnosing the cause of respiratory failure and applying only compressions in the belief they are saving lives. When one asks during a training session about respiratory assist, one is told chest compressions only is the new standard.

Studies have shown that cardiac arrest is secondary to respiratory arrest in these patients. Two case reports showed that naloxone was ineffective in keeping children alive (http://bit.ly/2hmzt08), and many more case reports showed naloxone is ineffective.

Would you say respiratory assist is essential for anyone who presents with coma, Cheyne-Stokes respiration, cyanosis, and miosis? These laypersons are eager to follow a clinician's instructions to save lives. — J. Gary Thompson, Toronto ON

Dr. Roberts responds: I agree that it makes no sense to avoid assisted ventilations for someone critically ill or even in cardiac arrest from opioids. The problem is identifying those caused by opioids, but your description certainly helps. Note that the current ACLS guidelines do not recommend naloxone for opioid-induced cardiac arrest. Likely once the heart has arrested from opioid-induced respiratory arrest, little will help, but if anything will, it is ventilations. I would assume that since naloxone has no direct effect on the heart, this drug will not help one that is asystolic, but in an otherwise healthy heart, providing oxygen might start it up again. Since cardiac arrest is due to prolonged respiratory arrest, it is not surprising that naloxone would provide no benefit for those who are dead.

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