Coronary artery disease: Chronic stable angina

Introduction to Chronic Stable Angina

Coronary artery disease is a condition due to imbalance in oxygen demand and supply resulting predominantly from atherosclerotic disease of the coronary artery.
Its incidence is on the rise worldwide as a result of epidemiologic transition from communicable to non-communicable diseases.

Risk factors for Chronic Stable Angina

  1. Diabetes mellitus
  2. Hypertension
  3. Cigarette smoking
  4. Obesity
  5. Dyslipidaemia
  6. Advanced aging
  7. Male gender

Pathogenesis of Chronic Stable Angina

Atherosclerosis is the major underlying pathogenic factor (See diagram below)

Pathogenesis of Coronary artery disease

Epicardial coronary artery stenosis:

  • 60% occlusion is compensated for at rest
  • 60%-90% occlusion causes ischaemia when there is increased oxygen demand
  • 90% occlusion results in ischaemia even at rest

Chronic stable angina (angina pectoris)

Clinical features

Symptoms

  • Typically retrosternal chest pain or
    heaviness worsened by exertion that radiates to the left upper arm

Angina equivalents include:

  • Dyspnoea
  • Palpitation
  • Giddiness
  • Fatigue
  • Silent ischemia may occur in the diabetics & elderly

Signs

There may be no specific abnormal finding.
Nicotine stain of the nails and cardiomegaly may be observed

Differential diagnoses

  1. Pulmonary embolism
  2. Gastro-esophageal (GERD)
  3. Pericarditis
  4. Aortic dissection
  5. Mitral valve prolapse syndrome
  6. Esophageal spasm
  7. Costochondritis

Investigations

Resting ECG:

  • Normal in 50% of patients
  • ST depression
  • May show Q wave of previous MI

Exercise stress ECG:

  • Positive test evidenced by ST depression ≥ 1 mm (planar or down sloping)
  • Arrhythmias or fall in BP
  • Sensitivity (68%);
  • Specificity (77%)

Echocardiography
Laboratory evaluation:

  • Fasting Blood Glucose
  • Lipid profile
  • Electrolytes, urea & creatinine

Coronary angiography: Gold standard.
invasive, expensive & done only when
coronary artery bypass graft CABG or
angioplasty is planned.

Treatment for Coronary artery disease

Antipatelet therapy:

  • Acetylsalicylic acid: 75 mg orally daily

Or:

  • Clopidogrel 75 mg orally daily

Lipid lowering drugs:

  • HMG-CoA reductase inhibitors
  • Atovarstatin 10-20 mg orally daily

Nitrates:

  • Short acting Glycerin Trinitrate tablets 0.3 – 1mg sublingually, repeated as required; 400
    microgramspray/metered dose 1-2 doses under tongue

OR

  • Intravenous infusion, 10-200
    micrograms/minute, adjusted according to response; max. 400 micrograms/minute

Long acting Isosorbide dinitrate 30-120 mg three times daily, and up to 240 mg if required

Or

Intravenous infusion, 2-10 mg/hour, higher doses up to 20mg/hour may be required
Betablockers:

  • Cardioselective (atenolol 50-100 mg
    daily; metoprolol 50-200 mg daily).
  • Target pulse rate of 55-60 bpm
  • Taper over 3-10 days

Calcium channel blockers

  • Dihydropyridine
    • Amlodipine 5-10 mg daily

Or:

    • Nifedipine 20-60 mg daily

Or:

  • Non-dihydropyridine:
    • Verapamil 80-120 mg 8 hourly

Angiotensin converting enzyme inhibitor:

  • Captopril 6.25 12.5 mg daily.
  • Other  ACEIs may be used in patients with hypertension

Angiotensin receptor blockers:

  • Valsartan 80-160 mg daily

Revascularization:

  • Percutaneous coronary intervention
  • Coronary artery bypass graft