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PA26.6 | Ischaemic Heart Disease & Acute Coronary Syndromes — SDL Guide (Part 4)

Special Situations — Variant Angina and Sudden Cardiac Death

A three-panel medical diagram compares reversible coronary vasospasm in variant angina with the ischaemia-induced ventricular fibrillation mechanism of sudden cardiac death. — **Panel A:** Coronary artery lumen, coronary vasospasm, contracted vascular smooth muscle, atheromatous plaque, reduced coronary blood flow, restored coronary blood flow, transient ST elevation, ECG baseline recovery, nitrates, calcium-channel blockers.. **Panel B:** Rest pain, early morning onset, transient episode timeline, normal troponin, normal CK-MB, prolonged spasm exception, avoid beta-blockers, nitrates, calcium-channel blockers.. **Panel C:** Heart, major coronary artery, severe atherosclerotic stenosis greater than 75%, acute plaque change, healed prior MI scar, ischaemia-induced electrical instability, ventricular fibrillation ECG, sudden cardiac death within 1 hour, implantable cardioverter-defibrillator, statin, antiplatelet therapy..

Variant (Prinzmetal) Angina:
Coronary vasospasm causes transient, severe reduction or complete cessation of coronary blood flow. Occurs at rest (often early morning), associated with transient ST elevation on ECG that resolves completely. Pathology: severe but reversible vasospasm, often at the site of an atheromatous plaque. Treated with calcium-channel blockers and nitrates; avoid beta-blockers. Troponin typically remains normal unless spasm is prolonged.

Sudden Cardiac Death (SCD):
- Defined as unexpected death within 1 hour of symptom onset, from a cardiac cause
- IHD (atherosclerosis ± acute plaque change) accounts for >80% in adults
- Mechanism: ventricular fibrillation triggered by ischaemia-induced electrical instability
- Pathological finding at autopsy: >75% stenosis in at least one major coronary artery; acute plaque change in ~50%; healed prior MI scars common
- Prevention: implantable cardioverter-defibrillators (ICDs) in patients with prior MI and reduced EF; statins/antiplatelets for secondary prevention

SELF-CHECK

A 48-year-old male smoker with no prior cardiac history is found to have the following test results 6 hours after onset of severe chest pain: Troponin I = 0.02 ng/mL (ref <0.04), CK-MB = 4 U/L (ref <25), ECG shows 1 mm ST depression in leads V4–V6. He is admitted and troponin is repeated at 3 hours: Troponin I = 0.18 ng/mL. What is the MOST LIKELY diagnosis?

A. Unstable angina — troponin is still below the diagnostic threshold

B. STEMI — ST changes confirm complete coronary occlusion

C. NSTEMI — rising troponin (delta) with ischaemic ECG changes but no ST elevation

D. Stable angina with demand ischaemia

Reveal Answer

Answer: C. NSTEMI — rising troponin (delta) with ischaemic ECG changes but no ST elevation

NSTEMI = ACS + rising troponin (the 'delta' — a rise from 0.02 to 0.18 ng/mL over 3h clearly crosses the diagnostic threshold) + ischaemic ECG changes (ST depression V4–V6) WITHOUT ST elevation. Unstable angina would show no troponin rise. STEMI requires ST elevation. Stable angina produces no biomarker change and symptoms only with exertion.

High-Yield Summary Table

Four-panel medical summary comparing stable angina, unstable angina, NSTEMI, and STEMI by coronary occlusion, ECG findings, troponin pattern, and MI type. — **Panel A:** Coronary artery cross-sections showing fixed stenosis, partial transient thrombus, partial sustained thrombus, complete thrombotic occlusion, subendocardial injury, and transmural injury.. **Panel B:** ECG comparison showing ST depression with exertion, ST depression or T-wave inversion, and ST elevation patterns.. **Panel C:** Troponin time-course graph showing normal baseline in angina and rise-and-fall elevation in myocardial infarction.. **Panel D:** High-yield comparison table listing syndrome, mechanism, occlusion, ECG change, troponin status, and MI type..

Use this table for rapid revision:

Syndrome	Mechanism	Occlusion	ECG	Troponin	MI type
Stable Angina	Fixed stenosis	None	ST↓ (exertion)	Normal	None
Unstable Angina	Partial thrombus	Partial, transient	ST↓/T↓	Normal	None
NSTEMI	Partial, sustained	Partial, sustained	ST↓/T↓	↑↑ (rise+fall)	Subendocardial
STEMI	Complete occlusion	Complete	ST↑, Q waves	↑↑↑	Transmural
Variant Angina	Vasospasm	Transient complete	Transient ST↑	Usually normal	None (unless prolonged)

MI evolution timeline (must memorise):
• 0–12h: normal light microscopy / wavy fibres
• 12–24h: coagulative necrosis + contraction bands
• 1–3d: neutrophils (PMN peak)
• 3–7d: macrophages + phagocytosis
• 1–2wk: granulation tissue
• >2wk–2mo: dense collagen scar

Biomarker rule-of-thumb: Myoglobin rises first (1–3h), CK-MB peaks and returns fastest (48–72h, useful for reinfarction), Troponin is most sensitive/specific and stays longest (TnT up to 14d).