Unstable angina

Pathophysiology - Cracking Plaques

• Foundation: Atherosclerosis leads to vulnerable plaques in coronary arteries.
• Plaque Morphology: Characterized by a thin, rupture-prone fibrous cap over a large, inflammatory lipid-rich necrotic core.
• The Event: Spontaneous or stress-induced rupture/erosion of the plaque exposes its highly thrombogenic contents (e.g., collagen, tissue factor) to the blood.
• Thrombus Formation: This triggers rapid platelet adhesion and aggregation, forming a non-occlusive, platelet-rich (white) thrombus.
• Result: The thrombus reduces coronary blood flow, causing myocardial ischemia and anginal symptoms, but without complete vessel blockage.

⭐ Unstable Angina (UA) and NSTEMI exist on a continuum, sharing the same pathophysiology. The key difference is the severity and duration of ischemia: in UA, it's insufficient to cause detectable myocyte necrosis (i.e., cardiac biomarkers are negative).

Clinical Presentation & Diagnosis - The Heart's Cry

• Chest Pain: Retrosternal, crushing/pressure, radiating to arm/jaw.
  • New onset: Severe, limiting activity.
  • Crescendo: ↑ frequency, duration, or intensity.
  • At rest: Lasting > 20 minutes.
• Physical Exam: Often normal; may show diaphoresis, S4 gallop, or signs of heart failure.

⭐ Key Discriminator: Unstable Angina is defined by the absence of elevated cardiac enzymes (troponins). It represents myocardial ischemia without infarction.

Risk Stratification - Scoring Severity

• TIMI Score: Estimates mortality for patients with UA/NSTEMI. One point for each risk factor.

• HEART Score: Predicts 6-week risk of Major Adverse Cardiac Events (MACE).

⭐ HEART Score Components: History, ECG, Age, Risk factors, Troponin. A score of 0-3 is low risk and supports discharge.

Management - Code Red Care

Initial therapy aims to stabilize the patient and prevent further thrombosis.

📌 MONA-BASH

• Morphine: For refractory angina.
• Oxygen: Supplemental, only if O₂ saturation < 90%.
• Nitrates: Sublingual or IV for active pain. ⚠️ Caution: Avoid in hypotension, RV infarction, or recent PDE5 inhibitor use.
• Antiplatelet Therapy:
  • Aspirin (162-325 mg) chewed immediately, followed by daily 81 mg.
  • P2Y12 inhibitor (e.g., clopidogrel, ticagrelor).
• Beta-blocker: Start within 24 hours if no signs of heart failure or shock.
• Anticoagulation: LMWH (enoxaparin) or UFH.
• Statin: High-intensity (e.g., Atorvastatin 80 mg) initiated early.

⭐ In cocaine-induced ACS, avoid beta-blockers due to the risk of unopposed alpha-stimulation. Use benzodiazepines for anxiety and sympathetic surge.

High‑Yield Points - ⚡ Biggest Takeaways

• Unstable Angina is new-onset, accelerating, or rest angina representing acute myocardial ischemia.
• It is distinguished from NSTEMI by normal cardiac biomarkers; there is no myocardial necrosis.
• EKG findings are often transient ST-segment depression or T-wave inversions, but can be normal.
• Caused by a non-occlusive thrombus over a disrupted atherosclerotic plaque.
• Management focuses on antiplatelet and anticoagulant therapy to prevent progression to MI.
• Risk stratification (e.g., TIMI score) is crucial to guide timing for angiography.