⚡ Sudden cardiac death (SCD) refers to an unexpected death caused by an abrupt loss of heart function. While rare in the young, it is devastating and often highly publicised. In older adults 👴, SCD is usually linked to coronary artery disease (CAD), whereas in younger people 👦👩‍🦱 it is more commonly due to cardiomyopathies or inherited ion-channelopathies.

📌 About

👨‍🦱 SCD is significantly more common in young males.
🏃‍♂️ College athletes face a 2–3× higher incidence, often due to hidden structural heart disease like arrhythmogenic right ventricular cardiomyopathy (ARVC).

🧬 Heritable Causes

Hypertrophic Cardiomyopathy (HCM): Prevalence ~1 in 500; a leading cause of athletic SCD.
Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC): Fibrofatty infiltration of the RV myocardium → ventricular arrhythmias.
Dilated Cardiomyopathy: Ventricular dilation + impaired contraction.
Left Ventricular Non-Compaction: Excess trabeculae → impaired systolic/diastolic function.
Heritable Channelopathies:
- ⏱️ Long QT Syndrome (LQTS): ~1 in 2,000; predisposes to torsades de pointes.
- ⚡ Short QT Syndrome: Rare, linked with malignant arrhythmias.
- 🔥 Brugada Syndrome: Characteristic ECG with risk of VF arrest.
- 🏋️ Catecholaminergic Polymorphic VT (CPVT): Exercise or stress-triggered arrhythmias.

🫀 Structural Congenital Heart Disease (CHD)

Combination of scarring, hypertrophy, and fibrosis predisposes to arrhythmias even after corrective surgery.
Tetralogy of Fallot: Classic example, with ongoing SCD risk (0.1–0.2% per year post-repair).

🩺 Structurally Normal Heart (but electrical risk)

🔥 Brugada Syndrome: ST elevation V1–V3, VF risk.
⏱️ Congenital LQTS: Prolonged QTc → torsades risk.
💊 Acquired LQTS: Drugs/electrolyte imbalance.
⚡ Pre-Excitation Syndromes (e.g., WPW): AF with rapid conduction → VF risk.
🏏 Commotio Cordis: Chest trauma during vulnerable repolarisation phase → VF arrest.
😰 Catecholamine-Induced VT: Stress or exertion triggers malignant arrhythmia.

❤️ Structurally Abnormal Heart

Ischaemic Heart Disease (IHD): 🫀 ACS or MI precipitating VF/VT.
ARVC / ARVD: Fibrofatty replacement of RV → malignant arrhythmias.
Hypertrophic Cardiomyopathy: Thick walls, arrhythmia-prone myocardium.
Aortic Stenosis: Severe LV outflow obstruction → exertional syncope, arrhythmia risk.

🧾 Causes of Sudden Cardiac Death

💡 SCD is not always purely cardiac - non-cardiac triggers exist too.

Category	Cause	Clinical Details	Diagnostic Details
🫁 Noncardiac	🧠 CNS Hemorrhage	Sudden neuro decline → cardiac arrest	CT/MRI brain
	🫁 Massive Pulmonary Embolus	Right heart strain & collapse	CT-PA, D-dimer
	💊 Drug Overdose	Cardiotoxicity/CNS depression	Toxicology screen
	🌬️ Severe Lung Disease (Hypoxia)	Respiratory failure → arrest	ABG, CXR, sats
	🩸 Aortic Dissection	Acute chest/back pain → collapse	CT angiogram
❤️ Cardiac	⚡ Ventricular Fibrillation	Chaotic rhythm → immediate collapse	ECG, defibrillation
	🫀 Myocardial Ischaemia	Reduced coronary flow → arrhythmia	ECG, troponins
	⏱️ Long QT Syndrome	QT prolongation → torsades	ECG, genetics
	⚡ Brugada Syndrome	ST elevation V1–V3 → VF risk	ECG ± sodium channel blocker challenge
	🏋️ Ventricular Tachycardia	Rapid broad-complex VT → collapse	ECG, EPS
	🐢 Bradyarrhythmias	Sinus pauses, AV block → syncope/arrest	ECG, Holter
	🔒 Aortic Stenosis	LV outflow obstruction → exertional collapse	Echocardiogram
	🩸 Pericardial Tamponade	Fluid compressing heart	Echo, pericardiocentesis
	🦠 Endocarditis Complications	Valve destruction/emboli → sudden arrest	Echo, cultures
	💔 Hypertrophic Cardiomyopathy	Arrhythmia or LVOT obstruction	Echo, MRI, genetics
	🩹 Kawasaki Arteritis	Coronary aneurysm rupture/occlusion	Echo, angiography

🔍 Investigations

📈 ECG: Key screening tool for LQTS, WPW, HCM, Brugada.
👩‍⚕️ Clinical History & Exam: Syncope, family history, exertional symptoms.
🫀 Echocardiography: Structure & function - cardiomyopathies, valve disease.

📊 ECG Findings Raising SCD Risk

⏱️ QTc >450ms (men), >470ms (women).
⬇️ T-wave inversion, prolonged QRS, LBBB.
⚡ Non-sustained VT episodes on Holter.
💔 Poor LV function (echo, MRI).

🛠️ Management

ICD (Implantable Cardioverter-Defibrillator): 💡 Life-saving in high-risk patients, but consider device-related complications in younger patients.
Device Complications: ⚠️ Inappropriate shocks, lead malfunctions, anatomical challenges in children/young adults.

📚 References

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Sudden Cardiac Death (SCD)