Causes of Cardiac Arrest in Teenagers
The primary causes of sudden cardiac arrest in teenagers are heritable cardiomyopathies (especially hypertrophic cardiomyopathy) and inherited channelopathies (particularly long QT syndrome), followed by structural congenital heart disease, myocarditis, and coronary artery abnormalities 1.
Major Etiologic Categories
Heritable Cardiomyopathies
These represent the most common structural causes:
- Hypertrophic cardiomyopathy (HCM) - Most prevalent, occurring in approximately 1:500 persons 1
- Arrhythmogenic right ventricular cardiomyopathy (ARVC)
- Dilated cardiomyopathy
- Left ventricular non-compaction cardiomyopathy
These conditions are highly treatable when identified, making them critical targets for screening 1.
Inherited Channelopathies (Ion Channel Disorders)
These electrical disorders occur without structural heart abnormalities:
- Long QT syndrome (LQTS) - Incidence approximately 1:2,000 persons 1
- Brugada syndrome
- Catecholaminergic polymorphic ventricular tachycardia (CPVT) - Notably has the highest incidence of sudden cardiac arrest at 45%, with 77% presenting with exercise-related syncope or arrest 2
- Short QT syndrome
Critical clinical pearl: CPVT patients typically present with exercise-induced syncope or sudden cardiac arrest, making any exercise-related syncope a red flag requiring immediate cardiac evaluation 2.
Structural Congenital Heart Disease
Approximately 40,000 children are born annually with congenital heart disease in the United States. These patients have elevated risk compared to the general population, with sudden cardiac arrest accounting for 15-25% of deaths, particularly as they age into adolescence and early adulthood 1. The combination of ventricular dysfunction, scarring, hypertrophy, and fibrosis increases sudden cardiac arrest risk 1.
Acquired Conditions
- Myocarditis - Represents a significant proportion of structural causes at autopsy 3
- Anomalous coronary arteries - Particularly anomalous origin of the left coronary artery from the right sinus of Valsalva (ALCA-R), which most commonly presents with exercise-related chest pain, syncope, or sudden cardiac arrest 2
- Substance-related cardiac toxicity - Including cocaine, amphetamines, and anabolic steroids 4
- Commotio cordis - Blunt chest trauma causing ventricular fibrillation 5
Additional Risk Factors
- Wolff-Parkinson-White syndrome - Ventricular preexcitation carries a small but real risk of sudden cardiac arrest even in asymptomatic patients 6, 5
- Systemic conditions - Sarcoidosis, chronic kidney disease, and autonomic dysfunction 4
Epidemiologic Patterns
Age-dependent risk: After early infancy, the prevalence of sudden cardiac death falls in early childhood and begins rising again in adolescence 1. The incidence ranges from 1-2 per 100,000 person-years in Western countries 4.
Gender disparity: Males have approximately 2:1 higher risk compared to females across all teenage years 1.
Unexplained Sudden Cardiac Death
A critical caveat: Even with comprehensive autopsy, 6-40% of sudden cardiac deaths in young people remain unexplained 3. These cases are often attributed to cardiac channelopathies (ion channel dysfunction) that are undetectable on conventional autopsy, emphasizing the importance of genetic testing and family screening even when no structural cause is found 3.
Clinical Presentation Patterns
Family history is the most common reason for identification of patients with LQTS and HCM before symptoms occur 2. However, ALCA-R typically presents with symptoms (exercise chest pain or syncope), and CPVT has the highest rate of presenting as sudden cardiac arrest itself 2.
Warning symptoms to never dismiss:
- Exercise-related chest pain, syncope, or near-syncope (not vasovagal)
- Unexplained dyspnea or excessive fatigue with exercise
- Palpitations during exercise
- Family history of sudden death before age 50
The diagnostic evaluation requires ECG and echocardiography as fundamental tools, with cardiac MRI, exercise stress testing, and genetic testing added based on clinical suspicion 3, 6.