Ch10: Coronary Heart Disease

Preparatory Mindset

Coronary heart disease (CHD / ischaemic heart disease) is the number-one cardiovascular exam topic and the leading cause of adult death worldwide (~25% of all deaths). The core skill is the ACS spectrum: stable angina → unstable angina (UA) → NSTEMI → STEMI — one disease continuum (ruptured coronary plaque + thrombosis), differing in whether the artery is fully occluded (STEMI) and whether myocardial necrosis has occurred (troponin rise) (CM exam tested). Exam essentials: (1) chest-pain differential and ECG/infarct-location mapping (II/III/aVF = inferior, V1–V3 = anteroseptal, etc.), (2) "Time is muscle" reperfusion — primary PCI within 12 h, fibrinolytic if PCI unavailable, (3) the antiplatelet + anticoagulant + anti-ischaemic cocktail (aspirin + P2Y12 inhibitor + LMWH + nitrate + β-blocker + statin + ACEi), and (4) risk stratification (GRACE, high-risk features). The HKHA ACS protocol is LMCHK-critical — commit the drug doses to memory.

Core Concepts

Definition & epidemiology

• CHD/IHD = myocardial ischaemia from an imbalance between coronary blood supply and myocardial demand — almost always due to coronary atherosclerosis.
• Age >40 y; leading cause of death (~25% of deaths); accounts for 30–35% of acute coronary syndromes and 45–50% of chest-pain presentations (15% will infarct) (17CM & 18CM exam tested).
• Risk factors: smoking, hypertension, diabetes, dyslipidaemia, family history, age, male sex, obesity, sedentary lifestyle.

Pathophysiology

• Atherosclerotic plaque → plaque rupture/erosion → platelet activation + thrombosis → partial occlusion (UA/NSTEMI) or complete occlusion (STEMI).
• Chronic stable angina = fixed stenosis with demand-supply mismatch (exertional); ACS = acute plaque event (rest).
• VEC (vascular endothelial cell) dysfunction and SMC (smooth muscle cell) proliferation are the cellular basis of the plaque.

Clinical classification

NSTE-ACS = UA + NSTEMI (no persistent ST elevation); ACS = UA + NSTEMI + STEMI; CCS = chronic coronary syndrome (stable).

Diagnosis

- Inferior: II, III, aVF (RCA); Lateral: I, aVL, V6 (LCX); Anteroseptal: V1–V3 (LAD); Anterolateral: V4–V6; Anterior: V1–V6 (LAD); Right ventricular: V3R, V4R.

• History: chest pain — retrosternal pressure/crushing, radiating to left arm/jaw, exertion/emotion-induced, relieved by rest/nitrates; duration >20 min at rest, diaphoresis, dyspnoea → ACS; atypical (neck ache, epigastric pain) in elderly/diabetic — "Treatment Delayed is Treatment Denied".
• ECG: stat + serial (at least daily ×3 days for MI evolution); ST-elevation criteria — new ST elevation at J-point in ≥2 contiguous leads: ≥2.5 mm (men <40 y), ≥2 mm (men ≥40 y), ≥1.5 mm (women) in V2–V3; ≥1 mm in other leads (no LVH/LBBB).
• Infarct location by ECG leads:
• Cardiac biomarkers: hs-troponin (rule-in/rule-out — ESC 0h/1h algorithm), CK-MB; serial.
• Imaging: stress ECG (treadmill — ≥2.0 mm ST depression, or ≥1 mm in stage I = positive), stress echo/nuclear, coronary CT angiography, PET-CT; coronary angiography (DSA) = gold standard for anatomy; echocardiogram (wall motion, EF).
• Differential: aortic dissection, PE, pericarditis, oesophageal spasm, GERD, musculoskeletal, panic; also heart failure, arrhythmia.

Management — stable angina

• Lifestyle + risk-factor control (smoking cessation, BP/lipids/DM, weight).
• Anti-ischaemic: sublingual nitrates (0.6 mg or spray) for attacks; β-blocker (reduce HR/BP, first-line); calcium-channel blocker or long-acting nitrate if β-blocker contraindicated; ivabradine.
• Secondary prevention "ABCDE": Aspirin/antiplatelet, BP control, Cholesterol (statin), Diabetes control, Exercise/Edu.
• Revascularisation (PCI/CABG) for refractory symptoms or high-risk anatomy.

Management — NSTE-ACS (UA/NSTEMI)

• Admit CCU if very high/high risk; bed rest + continuous ECG monitoring; ECG stat + serial ×3 days; serial hs-troponin (0h/1h algorithm); CXR, lipids within 24 h; correct precipitant (anaemia, hypoxia, tachyarrhythmia); morphine 2–5 mg IV if pain not relieved by nitrates; stool softener; O₂ only if SaO₂ <90%.
• Antithrombotic: Aspirin 160–320 mg loading → 80–100 mg daily; Clopidogrel 300–600 mg stat → 75 mg daily OR Ticagrelor 180 mg stat → 90 mg BD; LMWH — enoxaparin 1 mg/kg SC q12h (nadroparin weight-based).
• Anti-ischaemic: nitrates (SL TNG 1 tab q5 min ×3; IV TNG first 48 h for persistent ischaemia/HF/HTN; contraindicated if sildenafil within 24 h); β-blocker titrate to HR <70 (if not contraindicated).
• Other: statin regardless of baseline LDL; ACEi within first 24 h if LVEF <40% (ARB if intolerant); PPI if high GI-bleed risk.
• High-risk features (consult cardiologist → early invasive): haemodynamic instability, cardiogenic shock/acute HF, recurrent/refractory pain, life-threatening arrhythmia, established NSTEMI, dynamic new ST/T changes, GRACE >140.

Management — STEMI ("Time is muscle")

- ≤12 h of symptom onset + eligible → primary PCI (according to centre protocol). - PCI not available → fibrinolytic therapy (protocol per centre). - >12 h with persistent symptoms/haemodynamic instability → consider coronary angiogram ± PCI. - Not eligible for reperfusion → medical therapy (ACEi + statin + LMWH + nitrate).

- Symptomatic bradycardia: atropine 1 mg IV; pacing if unresponsive. - AV block: 1st degree & Mobitz I → conservative; Mobitz II or 3rd degree → temporary pacing (inferior MI with adequate narrow-QRS escape can be observed); also pace for bifascicular + 1st-degree, RBBB + alternating LAFB/LPFB, alternating LBBB/RBBB. - PSVT: ATP 10–20 mg IV; verapamil 5–15 mg IV (caution if low BP/β-blocker/reduced EF). - AF/flutter: digoxin 0.25 mg IV/PO loading (maintenance 0.0625–0.25 mg daily), diltiazem 5–15 mg IV, amiodarone 5 mg/kg over 60 min. - Wide-complex tachycardia: treat as VT until proven otherwise — amiodarone 150 mg IV over 10 min (repeat; then 600–1200 mg/24 h), lignocaine 1 mg/kg IV; synchronised cardioversion (100 J stable monomorphic; 200 J polymorphic). - Pump failure/cardiogenic shock: vasodilators (ACEi) if BP OK; inotropes (dopamine 2.5 μg/kg/min if SBP ≤90, titrate; dobutamine); mechanical circulatory support; revascularise.

• General: CCU bed; bed rest 12–24 h if uncomplicated; O₂ only if SaO₂ <90% (routine O₂ not recommended); morphine 2 mg IV PRN; serial ECG ×3 days; serial hs-troponin/CK-MB; lipids, HbA1c, baseline aPTT/INR (thrombolysis baseline).
• Reperfusion (the critical decision):
• P2Y12 inhibitor for PCI: clopidogrel 600 mg load → 75 mg daily; OR prasugrel 60 mg → 10 mg daily; OR ticagrelor 180 mg → 90 mg BD. For fibrinolysis: clopidogrel 300 mg (age ≤75; no load if >75) → 75 mg daily.
• LMWH: fibrinolysis age <75 — enoxaparin 30 mg IV bolus, then 1 mg/kg SC q12h (15 min later); age ≥75 — no bolus, 0.75 mg/kg SC q12h; up to 8 days or until revascularisation.
• β-blocker (metoprolol 25 mg BD oral if not decompensated HF); ACEi within 24 h (anterior MI/HF; starting doses: perindopril 1 mg, ramipril 1.25 mg, lisinopril 2.5 mg daily); nitrate if persistent pain/HF/HTN.
• Complications & treatment:
• Secondary prevention: aspirin, β-blocker, statin, ACEi (post-MI), cardiac rehab, smoking cessation, BP/DM control.

High-Yield Points

• ACS spectrum: stable angina → UA → NSTEMI (troponin+) → STEMI (ST elevation) — plaque rupture + thrombosis.
• Inferior MI = II, III, aVF (RCA); anterior = V1–V6 (LAD); RV = V3R/V4R.
• Reperfusion: ≤12 h → primary PCI; fibrinolytic if PCI unavailable; >12 h persistent symptoms → angiogram.
• O₂ only if SaO₂ <90% (no routine O₂).
• Antiplatelet: aspirin + clopidogrel/ticagrelor; LMWH enoxaparin 1 mg/kg q12h.
• Statin regardless of LDL; ACEi if LVEF <40% (within 24 h); β-blocker HR <70.
• High risk: shock, recurrent pain, life-threatening arrhythmia, dynamic ST changes, GRACE >140.
• Wide-complex tachycardia = VT until proven otherwise; VF → defibrillate + adrenaline q3–5 min.
• Nitrate contraindicated if sildenafil within 24 h.

Topic Summary

CHD spans stable angina to the ACS continuum (UA, NSTEMI, STEMI) driven by coronary plaque rupture with superimposed thrombosis. Diagnosis combines the chest-pain history, serial ECGs with infarct localisation, and hs-troponin kinetics. Management is time-critical: antiplatelet + anticoagulant + anti-ischaemic therapy (aspirin, P2Y12 inhibitor, LMWH, nitrate, β-blocker, statin, ACEi) plus urgent reperfusion for STEMI (primary PCI ≤12 h, fibrinolysis if unavailable) and early invasive strategy for high-risk NSTE-ACS (GRACE >140, haemodynamic instability). Complications — arrhythmias (atropine, pacing, amiodarone, defibrillation), pump failure, AV block — are managed per the HKHA ACS protocol, which is an LMCHK priority.