Ischaemic Heart Disease & Coronary Revascularisation

❤️ IHD & Coronary Revascularisation

Stable angina, ACS, STEMI — CABG vs PCI indications, the LIMA–LAD graft, and cardiopulmonary bypass principles.

The IHD Spectrum

Ischaemic heart disease exists on a spectrum from stable angina (fixed plaque, supply-demand mismatch) through acute coronary syndromes (plaque rupture) to ST-elevation myocardial infarction (complete occlusion). The unifying pathology is atherosclerosis of the epicardial coronary arteries — but the clinical presentation, risk, and urgency differ fundamentally.

Condition	Pathology	ECG	Troponin	Immediate Management
Stable Angina	Fixed atherosclerotic plaque. Supply-demand mismatch on exertion. No plaque rupture or thrombus. Predictable, reproducible on exertion, relieved by rest/GTN.	ST depression on exercise testing; normal at rest	Normal	Sublingual GTN for acute episodes. Prophylaxis: beta-blockers, calcium channel blockers, long-acting nitrates. Statin, aspirin, ACE inhibitor. Risk factor modification. Revascularisation (PCI/CABG) if medically refractory or high-risk anatomy.
Unstable Angina (UA)	Plaque rupture + partial coronary occlusion (thrombus). Rest pain or crescendo pattern. No myocardial necrosis.	ST depression, T-wave inversion, or normal	Normal (no necrosis)	DAPT (aspirin + ticagrelor/clopidogrel), LMWH, nitrates, beta-blocker. GRACE score → early invasive angiography (within 24–72h) if high-risk.
NSTEMI	Plaque rupture + partial occlusion + myocardial necrosis (subendocardial). Troponin elevated distinguishes from UA.	ST depression, T-wave inversion (subendocardial pattern)	Elevated (peaks 12–24h)	As UA. GRACE score guides timing of invasive strategy. High-risk (raised troponin, haemodynamic instability): invasive within 24h. Very high-risk: immediate angiography.
STEMI	Complete coronary occlusion → transmural infarction of entire myocardial wall thickness. Time-critical.	ST elevation in territory (≥1mm limb leads, ≥2mm precordial) OR new LBBB	Elevated (peaks 12–24h, may be elevated on presentation)	Primary PCI within 90 min of first medical contact (preferred). Thrombolysis if PCI not available within 120 min. DAPT, anticoagulation, beta-blocker, statin, ACE inhibitor.

ECG Territory Localisation

Territory	Artery	ECG Leads	Complications
Anterior	LAD (Left Anterior Descending)	V1–V4	Anterior LV dysfunction. Cardiogenic shock. Bundle branch block. VT/VF. Anterior LV aneurysm.
Lateral	LCx (Left Circumflex)	I, aVL, V5–V6	Lateral wall motion abnormality. Often less haemodynamically significant.
Inferior	RCA (Right Coronary Artery — 85%) or LCx (15%)	II, III, aVF	RV infarction (check V4R). AV block (RCA supplies AV node in 85%). Bradycardia. Hypotension — give fluids not diuretics.
Posterior	RCA or LCx	Reciprocal ST depression V1–V2 (posterior STEMI). Dominant R wave in V1/V2.	Often missed. Apply posterior leads (V7–V9) — ST elevation confirms.

🧠 STEMI Territory Memory Aid

SIFL — Superior (anterior) = LAD; Inferior = RCA; Floor of mouth (Lateral) = LCx

Inferior STEMI → always do right-sided leads (V4R) to exclude RV infarction
RV infarction triad: Hypotension + Elevated JVP + Clear lung fields (in context of inferior STEMI)
Treatment: IV fluids (preload dependent), avoid nitrates/diuretics (will kill them)

GRACE Score — Risk Stratification in ACS

The GRACE (Global Registry of Acute Coronary Events) score predicts in-hospital and 6-month mortality in ACS. Includes: age, heart rate, systolic BP, creatinine, Killip class, cardiac arrest, ST deviation, and raised cardiac biomarkers.

Low risk (GRACE ≤108)

Invasive within 72h

Or consider conservative management

High risk (GRACE >108)

Invasive within 24h

Also: rising troponin, dynamic ECG changes, TIMI ≥3

Very high risk

Immediate angiography

Haemodynamic instability, VT/VF, refractory chest pain

STEMI target

≤90 min

First medical contact to balloon inflation (primary PCI)

Killip Classification — Heart Failure in ACS

Killip I: No signs of heart failure. 30-day mortality ~6%
Killip II: S3 gallop or basal rales. Mild LV dysfunction. Mortality ~17%
Killip III: Frank pulmonary oedema. Mortality ~38%
Killip IV: Cardiogenic shock (SBP <90 + end-organ hypoperfusion). Mortality ~81%. Emergency primary PCI ± IABP ± Impella.

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