Unstable Angina Pectoris

Part of the acute coronary syndrome (ACS) spectrum, characterized by:
  • New-onset, worsening, or rest angina
  • No myocardial necrosis (i.e., normal cardiac biomarkers)
Pathophysiologically: plaque disruption with non-occlusive thrombosis → transient ischemia

Aetiology

Primary Cause

  • Coronary Artery Disease (CAD) with plaque instability

Contributing Factors

Mechanisms
  • Plaque rupture or erosion
  • Platelet aggregation → non-occlusive thrombus
  • Vasoconstriction (endothelial dysfunction)
Precipitating Factors
  • Infection
  • Anemia
  • Tachyarrhythmias
  • Uncontrolled hypertension

Pathophysiology

Coronary Blood Flow Limitation
  • Fixed stenosis limits coronary flow reserve
  • At rest: adequate perfusion
  • During exertion: inadequate supply → ischemia
Ischemic Cascade
  1. ↓ Perfusion
  1. Metabolic changes (↓ ATP, ↑ lactate)
  1. Diastolic dysfunction
  1. Systolic dysfunction
  1. ECG changes
  1. Chest pain
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Epidemiology

  • Very common manifestation of chronic coronary syndrome
  • Prevalence increases with:
    • Age (>40 years)
    • Male sex (earlier onset)
  • Major global contributor to cardiovascular morbidity

Risk Factors

Modifiable
  • Smoking
  • Diabetes mellitus
  • Hypertension
  • Dyslipidemia
  • Obesity
  • Sedentary lifestyle
Non-Modifiable
  • Age
  • Male sex
  • Family history
 

Clinical presentation

Classical Symptom Complex (Typical Angina)
At least one of the following:
  1. Angina at rest (≥20 minutes)
  1. New-onset severe angina
      • Within last 1 month
      • Marked limitation (≥ CCS Class III
  1. Increasing frequency, severity, or duration (crescendo angina)
Character of Chest Pain (Important for Differentials)
Quality
  • Pressure, tightness, heaviness
  • “Crushing” sensation
  • More intense than
Location
  • Central (retrosternal)
  • Diffuse (patient uses whole hand, not a finger)
Radiation
  • Left arm (ulnar distribution)
  • Neck / jaw
  • Back / interscapular region
  • Occasionally right arm or epigastrium
Duration
  • >20 minutes
  • May be intermittent but recurrent
Precipitating & Relieving Factors
Triggers (↑ Myocardial O₂ Demand)
  • Physical exertion (walking uphill, climbing stairs)
  • Emotional stress
  • Cold weather (vasoconstriction)
  • Heavy meals (postprandial angina)
  • Sexual activity
Relief
  • Rest (↓ demand)
  • Sublingual nitrates (within 1–5 min)
 
Associated Symptoms (Autonomic & Ischemic)
  • Dyspnea (common “anginal equivalent”)
  • Diaphoresis
  • Fatigue
  • Nausea
  • Palpitations / Anxiety / “impending doom”
Anginal Equivalents (High-Yield)
Especially in:
  • Diabetes mellitus (autonomic neuropathy)
  • Elderly
  • Women
Presentation may include:
  • Dyspnea (most common)
  • Unexplained fatigue
  • Dizziness or syncope
Physical Examination Findings
Often subtle but critical for risk stratification
Possible Findings:
  • Normal exam (common)
  • Tachycardia (sympathetic activation)
  • Hypotension (poor cardiac output → high risk)
  • S3 gallop → LV dysfunction
  • S4 gallop → stiff ventricle (ischemia)
Signs Suggesting High-Risk Disease
  • Pulmonary edema
  • New mitral regurgitation murmur
  • Hemodynamic instability

Investigations

ECG
Key Principle
ECG changes are often dynamic and transient, so:
  • Serial ECGs are mandatory
Typical Findings
  • ST-segment depression (subendocardial ischemia)
  • T-wave inversion
  • Occasionally normal ECG
Clinical Interpretation
  • ST depression → higher risk
  • Dynamic changes → ongoing ischemia
 
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Cardiac Biomarkers
Troponin
  • Normal in unstable angina
  • Serial measurement required (0, 3–6 hours)
Elevated troponin → reclassify as NSTEMI
Risk Stratification Tools
TIMI Score (Thrombolysis in Myocardial Infarction)
  • Simple bedside risk assessment
  • Predicts 14-day risk of:
    • All-cause mortality
    • New/recurrent MI
    • Severe recurrent ischemia requiring urgent revascularization
Each variable = 1 point
Criteria
Explanation
Age ≥ 65 years
Increased baseline cardiovascular risk
≥3 CAD risk factors
(HTN, DM, dyslipidemia, smoking, family history)
Known CAD (≥50% stenosis)
Prior angiographic evidence
Aspirin use in last 7 days
Suggests aspirin resistance or severe disease
≥2 angina episodes in 24 h
Active ischemia
ST deviation ≥0.5 mm
Ischemic ECG change
Elevated cardiac biomarkers
Troponin/CK-MB positive
GRACE Score (More Accurate)
Includes:
  • Hemodynamics
  • Renal function
  • ECG findings

Management

Initial Stabilization
  • Oxygen
    • Only if SpO₂ <90% or respiratory distress
    • Start at 4 L/min
  • Nitrates
    • ISDN 5 mg / NTG 0.4-0.5 mg
    • Can be repeated every 5 minutes, max 3x
    • Sublingual/spray → IV if persistent pain
  • Aspirin + P2Y12 inhibitor (clopidogrel/ticagrelor)
    • Aspirin — chewed immediately (160–320 mg)
    • Clopidogrel 300 mg → maintenance 75 mg/day
    • Ticagrelor 180 mg → maintenance 2x90 mg/day
  • Morphine IV 1-5 mg
    • For severe, refractory pain
    • Can be repeated every 10-30 minutes
  • Beta-blocker
    • Unless contraindicated
Disease Modifying Therapy
Antiplatelet Therapy
  • Aspirin (first-line)
  • Clopidogrel if aspirin intolerance
Lipid-Lowering Therapy
  • High-intensity statins
  • Target: aggressive LDL reduction
ACE Inhibitors / ARBs
  • Especially in:
    • Diabetes
    • Hypertension
    • LV dysfunction
Revascularization
Indications
  • Persistent symptoms despite optimal medical therapy
  • High-risk findings on stress testing
  • Significant coronary stenosis
Modalities
1. Percutaneous Coronary Intervention (PCI)
  • Balloon angioplasty + stent
2. Coronary Artery Bypass Grafting (CABG)
  • Preferred in:
    • Left main disease
    • Triple vessel disease
    • Diabetics (better outcomes)