Question
A 59-year-old man is reviewed 4 weeks after being discharged following an acute ST-elevation myocardial infarction treated with primary PCI. He is clinically stable but anxious about his future risk. Which of the following factors is most strongly linked to the risk of sudden cardiac death during the first six months after a myocardial infarction?
A. Frequent isolated ventricular premature beats on monitoring
B. Ongoing tobacco use
C. Extensive coronary artery disease involving multiple vessels
D. Reduced left ventricular systolic function
E. Persistently elevated LDL cholesterol
Answer
D. Reduced left ventricular systolic function
Detailed discussion (exam relevance)
The single most powerful predictor of early and late mortality after myocardial infarction is left ventricular systolic dysfunction, usually quantified by a reduced left ventricular ejection fraction (LVEF). A low LVEF reflects the extent of irreversible myocardial damage and adverse ventricular remodelling, both of which create a strong substrate for malignant ventricular arrhythmias and progressive heart failure.
In the first six months post-MI, sudden cardiac death is most commonly due to ventricular tachyarrhythmias, particularly ventricular tachycardia degenerating into ventricular fibrillation. Patients with significantly impaired systolic function are at markedly higher risk—often quoted as 5–10 times higher mortality compared with those who preserve ventricular function.
Other factors listed in the question are important but less predictive in the early post-MI period. Ventricular ectopics, once thought to be high-risk, have been shown to be poor independent predictors unless they occur in the context of severe LV dysfunction. Cigarette smoking, while a major risk factor for recurrent infarction and long-term mortality, does not outperform LVEF in predicting early sudden death. Triple-vessel coronary disease predicts adverse long-term outcomes but does not correlate as strongly with early arrhythmic death as systolic failure. Elevated LDL cholesterol is a risk factor for atherosclerosis progression but has minimal short-term prognostic value immediately post-MI.
For MRCP candidates, it is crucial to link low LVEF → heart failure → electrical instability → sudden death. This is also the physiological basis for evidence-based therapies such as ACE inhibitors, beta-blockers, mineralocorticoid receptor antagonists, and in selected patients, implantable cardioverter-defibrillators (ICDs) once the myocardium has stabilised (usually ≥40 days post-MI).
Cheat sheet (exam-oriented)
- Strongest predictor of post-MI mortality: Low LVEF
- Mechanism of sudden death post-MI: Ventricular tachyarrhythmias
- New systolic heart failure post-MI: Indicates large infarct size
- Ventricular ectopics: Poor independent predictor without LV dysfunction
- Smoking: Long-term risk, not strongest early predictor
- 3-vessel disease: Prognostic for long-term outcomes
- LDL cholesterol: Minimal short-term prognostic value
- Key exam link: Low EF = arrhythmia + heart failure risk
- Therapies improving prognosis: ACEi, beta-blockers, MRAs
- ICD consideration: Persistent low EF after recovery phase
Flash cards
- Most important predictor of sudden death post-MI? → Low LVEF
- What does reduced EF reflect? → Extent of myocardial damage
- Commonest cause of death after MI? → Ventricular fibrillation
- Time window of highest arrhythmic risk post-MI? → First 6 months
- Pathophysiology linking MI to arrhythmia? → Scar-related re-entry
- Are ventricular ectopics strong predictors alone? → No
- Smoking increases what risk post-MI? → Recurrent events, long-term mortality
- Triple-vessel disease predicts what? → Adverse long-term prognosis
- LDL relevance immediately post-MI? → Low
- Clinical marker of large infarct size? → New systolic heart failure
- Drug class reducing sudden death risk post-MI? → Beta-blockers
- ACE inhibitors help by? → Preventing adverse remodelling
- EF threshold often considered high risk? → ≤35–40%
- ICD timing post-MI? → After stabilisation (≈40 days)
- Mechanism of ventricular fibrillation post-MI? → Electrical instability
- Early MI deaths usually due to? → Arrhythmia, not pump failure alone
- Inferior MI complication: → AV block
- Transmural MI early complication: → Acute pericarditis
- Late autoimmune pericarditis: → Dressler syndrome
- LV aneurysm risk: → Thrombus and embolic stroke
MCQs
1. The strongest predictor of sudden cardiac death within 6 months after MI is:
A. Smoking
B. Ventricular ectopics
C. Multivessel coronary disease
D. Reduced ejection fraction
E. Hypercholesterolaemia
Answer: D
2. Reduced LVEF post-MI primarily indicates:
A. Autonomic imbalance
B. Coronary spasm
C. Extent of myocardial necrosis
D. Valvular dysfunction
E. Volume overload
Answer: C
3. Most common immediate cause of death after MI:
A. Cardiogenic shock
B. Asystole
C. Ventricular fibrillation
D. Pulmonary embolism
E. Stroke
Answer: C
4. Ventricular ectopics post-MI are most concerning when:
A. Occurring at rest
B. Frequent but isolated
C. Associated with low LVEF
D. Suppressed by exercise
E. Present in smokers
Answer: C
5. Smoking after MI mainly increases risk of:
A. Early arrhythmic death
B. Recurrent atherosclerotic events
C. Mechanical complications
D. Dressler syndrome
E. Acute pericarditis
Answer: B
6. Triple-vessel disease best predicts:
A. Early sudden death
B. Long-term mortality
C. Bradyarrhythmias
D. Free wall rupture
E. Acute MR
Answer: B
7. LDL cholesterol post-MI is most relevant to:
A. Short-term arrhythmia risk
B. Acute pump failure
C. Long-term secondary prevention
D. AV block
E. Ventricular septal rupture
Answer: C
8. Which drug class most reduces sudden death risk post-MI?
A. Nitrates
B. Statins
C. Beta-blockers
D. Calcium channel blockers
E. Diuretics
Answer: C
9. ICDs are considered post-MI primarily for:
A. Frequent ectopics
B. Ongoing angina
C. Persistent low EF
D. Multivessel disease
E. High LDL
Answer: C
10. New systolic heart failure after MI implies:
A. Small infarct
B. Preserved myocardium
C. Extensive myocardial damage
D. Valvular disease
E. Right ventricular infarction only
Answer: C
11. Common cause of early post-MI pericarditis:
A. Autoimmune reaction
B. Infection
C. Transmural inflammation
D. Cholesterol emboli
E. Papillary muscle rupture
Answer: C
12. Dressler syndrome typically occurs:
A. Within 24 hours
B. 2–6 weeks post-MI
C. At 6 months
D. Only in NSTEMI
E. Only after PCI
Answer: B
13. LV aneurysm is associated with:
A. Low stroke risk
B. Transient ST elevation
C. Persistent ST elevation
D. Normal EF
E. Bradycardia
Answer: C
14. LV free wall rupture usually presents with:
A. Stable angina
B. Pulmonary oedema alone
C. Tamponade and shock
D. Fever and ESR rise
E. Wide pulse pressure
Answer: C
15. Papillary muscle rupture causes:
A. Aortic regurgitation
B. Acute mitral regurgitation
C. Tricuspid regurgitation
D. Ventricular septal defect
E. Pericardial effusion
Answer: B
16. Inferior MI is more commonly complicated by:
A. VF
B. AV block
C. LV aneurysm
D. Acute MR
E. Septal rupture
Answer: B
17. Best investigation to assess post-MI prognostic risk:
A. Lipid profile
B. Holter monitoring
C. Echocardiography
D. Exercise ECG
E. Troponin trend
Answer: C
18. Sudden death post-MI is most often due to:
A. Pump failure alone
B. Re-infarction
C. Malignant arrhythmia
D. Stroke
E. Sepsis
Answer: C
19. ACE inhibitors post-MI reduce mortality mainly by:
A. Lowering LDL
B. Preventing arrhythmias directly
C. Limiting ventricular remodelling
D. Increasing heart rate
E. Improving coronary flow
Answer: C
20. Which finding most strongly justifies aggressive secondary prevention?
A. Occasional ectopics
B. High LDL alone
C. Low EF
D. Smoking history alone
E. Age >60
Answer: C
Summary for quick exam revision
After myocardial infarction, the most powerful predictor of sudden cardiac death in the first six months is reduced left ventricular systolic function. A low ejection fraction reflects the extent of myocardial necrosis and adverse ventricular remodelling, creating a substrate for malignant ventricular arrhythmias, particularly ventricular tachycardia and ventricular fibrillation. Ventricular ectopics, smoking, multivessel coronary disease, and hypercholesterolaemia are all important but are weaker predictors of early sudden death when compared with LV dysfunction. New-onset systolic heart failure post-MI indicates a large infarct size and is associated with a several-fold increase in mortality. Evidence-based therapies such as beta-blockers and ACE inhibitors reduce mortality by limiting remodelling and arrhythmic risk. Assessment of ejection fraction with echocardiography is central to post-MI risk stratification and guides long-term management, including consideration of ICD therapy once the acute phase has passed.
Written for MRCP candidates by a practising physician. Content aligned with UK exam patterns and standard medical teaching.
Reference: Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine.