Sudden Cardiac Death — SAQ

Stem

A candidate is asked to manage a classic presentation of Sudden Cardiac Death in an exam setting. Use precise definitions, scores, doses, and decision thresholds.

Core knowledge (model answer backbone)

Sudden cardiac death (SCD) is the sudden, unexpected death from a cardiac cause occurring within one hour of symptom onset (witnessed), or within 24 hours of last being seen alive and well (unwitnessed). It is the leading natural cause of death in the industrialised world, accounting for roughly 300,000 to 400,000 events per year in the United States and 4 to 5 million globally. The final common pathway in 80 to 90 percent of cases is a ventricular tachyarrhythmia (rapid polymorphic VT degenerating to ventricular fibrillation), with bradyasystole and pulseless electrical activity accounting for the rest. Coronary artery disease underlies 75 to 80 percent of adult SCD; the remainder arise from cardiomyopathies (hypertrophic, dilated, arrhythmogenic right ventricular), inherited channelopathies (long QT, Brugada, CPVT), severe valvular disease, myocarditis, drug toxicity, electrolyte disturbance, anomalous coronary arteries, commotio cordis, and massive pulmonary embolism. Management is the chain of survival (early CPR, early defibrillation, early advanced life support), targeted temperature management at 32 to 36 degrees C for 24 hours, urgent coronary angiography when a cardiac cau

Red flags

• Survivor of cardiac arrest from VF or pulseless VT, not due to a fully reversible cause - secondary prevention ICD before discharge (AVID, CIDS, CASH trials); 30 to 50 percent one-year recurrence without one
• Commotio cordis - blunt, non-penetrative chest blow over the precordium during the 10 to 30 ms vulnerable window just before the T-wave peak triggers VF in a structurally normal heart - immediate CPR and defibrillation are the only effective therapy
• Syncope on exertion in a young athlete or with a family history of SCD under 40 - think HCM, ARVC, anomalous coronary, long QT, CPVT - restrict sport, ECG, echo, exercise test, cardiac MRI, genetic testing
• Family history of SCD in a first-degree relative under 40, or two or more relatives under 50 - mandatory cascade screening of first-degree relatives with ECG, echo, exercise test, and targeted genetic testing if a proband mutation is found

High-yield structure examiners expect

Cover: Overview & Definition, Classification, Epidemiology & Risk Factors, Pathophysiology, Clinical Presentation, Differential Diagnosis.

Key doses / thresholds (from topic teaching)

• ALS with adrenaline 1 mg IV every 3 to 5 min and amiodarone 300
• Adrenaline 1 mg IV after the 2nd shock, then every 3 to
• Amiodarone 300 mg IV after the 3rd shock, 150 mg after th
• Adrenaline 1 mg IV immediately, then every 3 to 5 min
• adrenaline 1 mg intravenously every 3 to 5 minutes** (s
• amiodarone 300 mg intravenous bolus after the third shock

Questions

a) Define the condition and give the most important classification or severity framework used in exams. (3 marks)

• Clear one-line definition matching standard teaching.
• Named classification / stages / types with discriminating features.
• One sentence on why classification changes management.

b) Outline pathophysiology in a mechanism chain that explains the main clinical features. (3 marks)

• Initiating insult → intermediate pathway → end-organ effect.
• Link at least two symptoms/signs to mechanism.
• Mention one complication pathway (e.g. shock, perforation, herniation, arrhythmia).

c) List discriminating clinical features and bedside assessment. (3 marks)

• Classic presentation plus one atypical group (elderly, pregnancy, child, immunocompromised).
• Named signs/manoeuvres if relevant.
• What must never be missed on exam/bedside (pregnancy test, airway, glucose, etc.).

d) Investigations with thresholds and one named score if applicable. (3 marks)

• First-line tests and what positive findings mean.
• Gold-standard or definitive investigation when needed.
• Score components reproduced exactly if a named score is standard for this topic.

e) Immediate resuscitation and definitive management with doses where standard. (3 marks)

• ABC / time-critical steps first.
• First-line drug(s) with agent + dose + route (or procedure steps).
• Escalation triggers (theatre, ICU, thrombolysis window, antidote, etc.).
• Disposition and safety-netting.

Marking tips

Full marks require specificity (numbers, names, doses) not generic "give antibiotics/fluids." Regional practice (ICMR / NICE / AHA) may be cited as alternative where relevant.