06. Non-Atherosclerotic Acute Coronary Syndromes
Not all acute coronary syndromes are caused by atherosclerotic plaque rupture. Non-atherosclerotic mechanisms require distinct diagnostic evaluation and conservative medical strategies.
1. Clinical Entities & Electrocardiographic Features
| Clinical Entity | Primary Pathophysiology | Clinical Demographics & Triggers | Electrocardiographic Signatures | First-Line Management Strategy |
|---|---|---|---|---|
| Spontaneous Coronary Artery Dissection (SCAD) | Non-traumatic, non-iatrogenic intramural hematoma $\pm$ intimal tear compressing true lumen. | Young/middle-aged females ($>80\%$), pregnancy/postpartum, fibromuscular dysplasia, emotional surge. | Classic STEMI, NSTEMI, or Wellens pattern depending on dissected vessel (LAD $>60\%$). | Conservative Medical Management (aspirin, beta-blockers) preferred over PCI due to high risk of iatrogenic propagation. |
| Prinzmetal (Vasospastic) Angina | Epicardial coronary artery hyperreactivity / severe focal spasm. | Young smokers, nocturnal resting chest pain (midnight to 8 AM), cold exposure. | Transient, reversible ST-segment elevation that resolves rapidly with sublingual nitrates. | Calcium Channel Blockers (Diltiazem/Amlodipine) + Long-acting Nitrates. Beta-blockers are contraindicated (unopposed $\alpha$-spasm). |
| MINOCA | MI with Non-Obstructive Coronary Arteries ($<50\%$ stenosis on angiogram). | Heterogeneous: plaque disruption, microvascular spasm, thromboembolism. | Dynamic ST-T changes with confirmed Troponin rise/fall. | Multimodality workup (CMR, intravascular ultrasound [IVUS], optical coherence tomography [OCT]). |
| Kounis Syndrome | Allergic / hypersensitivity-mediated coronary vasospasm or plaque rupture. | Drug allergies (antibiotics, NSAIDs), insect stings, contrast media. | ST elevation or depression during systemic anaphylactic/allergic reaction. | IM Epinephrine, Antihistamines, Corticosteroids, IV Nitrates/CCB for spasm. |
2. Multimodality Diagnostic Investigations
- High-Resolution Intravascular Imaging (IVUS / OCT): Identifies intramural hematoma in SCAD or plaque erosion/rupture in MINOCA.
- Cardiac Magnetic Resonance (CMR): Differentiates true ischemic MINOCA from non-ischemic mimics (Myocarditis and Takotsubo Cardiomyopathy).