General Medicine
Acute MI and Ischaemic Heart Disease
Acute myocardial infarction and ischaemic heart disease for MBBS: acute coronary syndrome classification, ECG triage, reperfusion, drug therapy and complications, mapped to NMC codes IM2.4 to IM2.21.
MedNext Academy | 3 min read
Acute MI and Ischaemic Heart Disease
Acute myocardial infarction and ischaemic heart disease for MBBS: acute coronary syndrome classification, ECG triage, reperfusion, drug therapy and complications, mapped to NMC codes IM2.4 to IM2.21.
This chapter covers the spectrum of ischaemic heart disease from stable angina to acute coronary syndrome, with emphasis on rapid ECG-based triage and reperfusion. It integrates the anti-ischaemic drug bundle, antiplatelet and statin therapy, complications and long-term secondary prevention.
High-yield: Acute MI and Ischaemic Heart Disease
- Acute coronary syndrome covers unstable angina, non-ST-elevation myocardial infarction and ST-elevation myocardial infarction, separated by the ECG and troponin.
- The universal definition of myocardial infarction requires a rise or fall in troponin plus ischaemic symptoms, ECG changes or imaging evidence.
- ST-elevation myocardial infarction is a clinical and ECG diagnosis that must not wait for troponin before reperfusion.
- Primary percutaneous coronary intervention is the preferred reperfusion strategy when it can be delivered within the recommended time window.
- When timely percutaneous intervention is unavailable, fibrinolysis should be given within 12 hours of symptom onset in ST-elevation infarction.
- The immediate anti-ischaemic bundle can be remembered as morphine, oxygen if hypoxic, nitrates, aspirin and a second antiplatelet.
- Dual antiplatelet therapy combines aspirin with a P2Y12 inhibitor such as ticagrelor, prasugrel or clopidogrel.
- High-intensity statin therapy is started early in all acute coronary syndrome patients regardless of baseline lipids.
- Reciprocal ST depression on the ECG supports a true ST-elevation infarction rather than pericarditis.
- Right ventricular infarction is preload dependent, so nitrates can cause dangerous hypotension and fluids are the initial treatment.
- Troponin is more sensitive and specific than the older CK-MB for myocardial injury.
- Mechanical complications such as papillary muscle rupture and ventricular septal rupture typically appear in the first days after infarction.
- Killip class stratifies mortality risk in acute infarction based on the degree of heart failure at presentation.
- Secondary prevention combines aspirin, a statin, a beta-blocker and an ACE inhibitor with lifestyle change.
- Cardiac rehabilitation after infarction reduces mortality and improves functional recovery.
Acute coronary syndrome at a glance
- **Triage:** ECG separates ST-elevation infarction from non-ST-elevation events; troponin confirms myocardial injury.
- **Reperfusion:** Primary percutaneous intervention is preferred; fibrinolysis within 12 hours if timely intervention is unavailable.
- **Initial drugs:** Aspirin plus a P2Y12 inhibitor, high-intensity statin, nitrates, and morphine or oxygen as needed.
- **Watch for:** Right ventricular infarct (avoid nitrates), mechanical complications and arrhythmia in the early days.
NMC competencies in this chapter
- **IM2.4:** Pathogenesis and natural history of ischaemic heart disease
- **IM2.5:** Definitions and classification of acute coronary syndrome
- **IM2.10:** Interpretation of the electrocardiogram in acute coronary syndrome
- **IM2.11:** Chest X-ray and cardiac biomarkers
- **IM2.15:** Medications used in acute coronary syndrome
- **IM2.16:** Thrombolysis, percutaneous intervention and bypass surgery
- **IM2.19:** Complications of acute coronary syndrome
- **IM2.21:** Advanced cardiac life support in acute coronary syndrome
Frequently Asked Questions
How is ST-elevation infarction distinguished from other acute coronary syndromes?
It is diagnosed on the ECG by persistent ST elevation or new left bundle branch block with ischaemic symptoms, and unlike other acute coronary syndromes it demands immediate reperfusion without waiting for troponin.
What is the preferred reperfusion strategy?
Primary percutaneous coronary intervention is preferred when it can be delivered within the recommended time window; otherwise fibrinolysis is given within 12 hours of symptom onset.
Why avoid nitrates in right ventricular infarction?
The right ventricle depends on preload to maintain output, so nitrates can drop preload and cause severe hypotension; the initial treatment is intravenous fluids instead.
How does this chapter help for NEET-PG?
ECG localisation, reperfusion timing, the antiplatelet and statin bundle and mechanical complications are recurring exam themes, so structured management knowledge maps straight to questions.
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