Write a short note on chronic coronary syndrome (stable angina) and non-invasive testing for myocardial ischaemia.

Definition

Chronic coronary syndrome (formerly stable ischaemic heart disease) is the stable phase of coronary artery disease, characterised by reversible myocardial ischaemia occurring when oxygen demand exceeds supply, without acute plaque rupture.

Stable angina is chest discomfort that is:

1. Retrosternal, of characteristic quality and duration

2. Provoked by exertion or emotional stress

3. Relieved by rest or nitrates within minutes

Typical angina has all three features; atypical angina has two; non-anginal chest pain has one or none — a simple classification that determines pre-test probability and hence which test to order.

Pathophysiology

Fixed atherosclerotic stenosis limits coronary flow reserve. Symptoms typically appear when the lumen is narrowed by more than 70%. Ischaemia begins in the subendocardium, which is most vulnerable because it is perfused last and compressed during systole — producing ST depression on the ECG.

Determinants of myocardial oxygen demand: heart rate, contractility and wall stress (preload and afterload) — which is exactly why beta-blockers, which reduce heart rate and contractility, are so effective.

Other mechanisms of angina: microvascular angina (angina with normal coronaries), vasospastic (Prinzmetal) angina (rest pain with transient ST elevation, responsive to calcium channel blockers, precipitated by smoking and cocaine), and secondary angina from anaemia, thyrotoxicosis, aortic stenosis or arrhythmia.

Clinical Assessment

History — the most important tool: site, character (heaviness, tightness, constriction — patients often clench a fist over the sternum, "Levine's sign"), radiation, provoking and relieving factors, duration (minutes, not seconds or hours), and stability over time.

Canadian Cardiovascular Society (CCS) grading:

Examination is often normal but should assess: risk factors, anaemia, thyroid status, blood pressure, murmurs (aortic stenosis is a critical differential), signs of heart failure, and peripheral vascular disease and carotid bruits as markers of generalised atherosclerosis.

Differential diagnosis: acute coronary syndrome, aortic dissection, pericarditis, pulmonary embolism, gastro-oesophageal reflux and oesophageal spasm, musculoskeletal chest wall pain, and anxiety.

Non-invasive Testing for Myocardial Ischaemia

The choice of test depends on pre-test probability, the ability to exercise, the baseline ECG, and local availability.

Choosing the test:

• Low to intermediate probability, able to exercise, interpretable ECG → exercise ECG or CT coronary angiography
• Unable to exercise → pharmacological stress (dobutamine echo or vasodilator perfusion imaging)
• Abnormal baseline ECG → an imaging-based test
• High probability with limiting symptoms → proceed to invasive coronary angiography

Invasive coronary angiography remains the gold standard for anatomy, and fractional flow reserve (FFR) assesses the functional significance of intermediate lesions — an important refinement, since anatomical severity does not always equate to ischaemia.

Management

1. Anti-anginal therapy — to relieve symptoms

• Beta-blockers — first-line; reduce heart rate, contractility and demand.
• Calcium channel blockers — alternative or add-on; non-dihydropyridines (verapamil, diltiazem) reduce rate but must not be combined with beta-blockers (risk of bradycardia and heart block) or used in heart failure; dihydropyridines (amlodipine) are safe with beta-blockers.
• Nitrates — sublingual for acute relief and prophylaxis before exertion; long-acting for prevention, with a nitrate-free interval to prevent tolerance.
• Second-line: ivabradine (rate reduction in sinus rhythm), ranolazine, nicorandil, trimetazidine.

2. Disease-modifying therapy — to prevent events (the more important half)

• Antiplatelet — aspirin (clopidogrel if intolerant).
• High-intensity statin for all, irrespective of baseline cholesterol; add ezetimibe or a PCSK9 inhibitor to reach targets.
• ACE inhibitor — particularly with diabetes, hypertension, LV dysfunction or CKD.
• Optimal control of blood pressure, diabetes and weight.
• SMOKING CESSATION — the single most effective intervention.
• Cardiac rehabilitation and structured exercise; Mediterranean-type diet; stress management.

3. Revascularisation

• PCI with stenting — relieves symptoms effectively; in stable disease it improves symptoms but has not been shown to reduce mortality or infarction compared with optimal medical therapy in most patients (the COURAGE and ISCHEMIA trials) — an important point that examiners like and that patients deserve to be told.
• CABG (coronary artery bypass grafting) — improves survival in left main stem disease, three-vessel disease (especially with LV dysfunction or diabetes), and complex anatomy (high SYNTAX score).
• Decisions are made by a heart team, weighing anatomy, comorbidity and patient preference.