Stable Angina Pectoris

Stable angina is reproducible exertional or stress-related chest discomfort from a fixed supply and demand mismatch, most often due to a flow-limiting epicardial atherosclerotic stenosis of 70% or more. It is the commonest first presentation of chronic coronary syndrome.

Annual incidence is about 1 to 2% in adults over 45 years, with prevalence rising steeply with age.

Risk factors are smoking, hypertension, dyslipidaemia, diabetes, obesity, chronic kidney disease and premature family history.

Annual cardiovascular death or infarction is about 1 to 3%, driven by extent of disease, left ventricular function and inducible ischaemia burden.

Pathophysiology is fixed luminal narrowing plus a reduced coronary flow reserve, with an ischaemic threshold that is stable over weeks.

Angina is graded by the Canadian Cardiovascular Society scale

• Class I: strenuous activity only.
• Class II: slight limitation (walking more than 2 blocks, stairs).
• Class III: marked limitation (walking 1 to 2 blocks).
• Class IV: symptoms at rest or with any activity.

Typical angina meets all three criteria

• Retrosternal pressure or tightness, with radiation to the left arm, jaw or back.
• Provoked by exertion, cold, meals or emotion.
• Relieved within 5 minutes by rest or sublingual nitroglycerin.
• Women, older adults and diabetics more often report dyspnoea, fatigue or epigastric discomfort. Walk-through angina and a second-wind phenomenon occur.
• Examination is often normal between episodes. Look for a fourth heart sound, ischaemic mitral regurgitation, xanthelasma, retinopathy and peripheral vascular disease.
• Red flags for unstable angina are new onset, crescendo pattern, rest pain over 20 minutes, or angina within 2 weeks of infarction.

• Pretest probability guides testing.
• Resting ECG, haemoglobin, HbA1c, lipids, creatinine, TSH and echocardiography are baseline.
• Coronary CT angiography is first line for low to intermediate probability.
• Stress imaging (echocardiography, perfusion SPECT or PET, cardiac MRI) suits intermediate to high probability or known disease.
• Exercise ECG has sensitivity near 68% and specificity near 77%, and is limited by baseline ECG abnormalities.
• Invasive angiography with fractional flow reserve (0.80 or less is significant) is reserved for high risk findings or refractory symptoms.
• High risk features are ischaemia over 10% of myocardium, ejection fraction under 40%, left main or proximal LAD disease.

Risk reduction (all patients)

• Aspirin 75 to 100 mg daily, or clopidogrel 75 mg daily if intolerant.
• Atorvastatin 40 to 80 mg or rosuvastatin 20 to 40 mg daily, targeting LDL cholesterol below 55 mg/dL, adding ezetimibe 10 mg then a PCSK9 inhibitor if needed.
• ACE inhibitor (ramipril 5 to 10 mg daily) for hypertension, diabetes, heart failure or kidney disease.
• Smoking cessation, exercise, weight loss, blood pressure below 130/80 mmHg.

Symptom control

• Sublingual nitroglycerin 0.4 mg, repeated every 5 minutes for up to 3 doses.
• First line: bisoprolol 2.5 to 10 mg daily, metoprolol succinate 50 to 200 mg daily, or diltiazem ER 180 to 360 mg daily. Do not combine a beta blocker with diltiazem or verapamil.
• Add amlodipine 5 to 10 mg, isosorbide mononitrate ER 30 to 120 mg (with a nitrate free interval), ranolazine 500 to 1000 mg twice daily, ivabradine 5 to 7.5 mg twice daily, or trimetazidine 35 mg twice daily.
• Refractory angina: enhanced external counterpulsation, coronary sinus reducer or spinal cord stimulation.

Revascularisation

• Indicated for refractory symptoms, left main disease of 50% or more, proximal LAD with multivessel disease, three vessel disease with diabetes or reduced ejection fraction.
• PCI with drug eluting stents suits low to intermediate SYNTAX scores. Bypass grafting suits complex multivessel disease, especially in diabetics.