🔬 Coronary Angiography

An invasive diagnostic procedure using X-ray fluoroscopy and iodinated contrast to visualise the coronary arteries and identify stenoses or occlusions.

The primary indications include the management of acute coronary syndromes (STEMI, NSTEMI, and unstable angina) to facilitate primary or urgent percutaneous coronary intervention (PCI). It is also indicated for the investigation of stable chest pain when non-invasive tests (such as CT coronary angiography) are inconclusive or suggest high-risk disease. Other indications include pre-operative assessment for valvular heart surgery and the investigation of unexplained heart failure or survived sudden cardiac death.

The procedure is performed in a cardiac catheterisation lab under local anaesthesia and often conscious sedation. Arterial access is typically gained via the radial artery (preferred in the UK) or the femoral artery. A catheter is advanced to the coronary ostia under fluoroscopic guidance, and a radiopaque iodine-based contrast medium is injected. Multiple X-ray projections are recorded to visualise the left and right coronary systems and their branches.

A normal angiogram demonstrates smooth, regular vessel walls without evidence of luminal narrowing, filling defects, or calcification. Contrast should flow briskly to the distal aspects of all major epicardial vessels (Left Main, Left Anterior Descending, Circumflex, and Right Coronary Artery) and their branches, reaching the microvasculature (TIMI 3 flow). There should be no evidence of collateral vessel formation or anatomical anomalies.

Interpretation involves a systematic visual or quantitative assessment of the coronary tree. The degree of stenosis is expressed as a percentage reduction in luminal diameter across multiple orthogonal views. Fractional Flow Reserve (FFR) or Instantaneous Wave-free Ratio (iFR) may be used during the procedure to assess the physiological significance of borderline (50-70%) stenoses. Results are used to classify disease as single, double, or triple-vessel, which informs the Heart Team's decision-making process.

Significant coronary artery disease is identified by luminal narrowing of >50% in the left main stem or >70% in major epicardial vessels. Findings may include discrete eccentric stenoses, diffuse 'pipe-stem' calcification, or total occlusions with collateralisation. In the context of ACS, features of plaque rupture (ulcerated margins or filling defects suggesting thrombus) are critical. Non-obstructive coronary artery disease (MINOCA) may also be identified where clinical symptoms exist without epicardial stenosis.

Coronary angiography remains the 'gold standard' for defining coronary anatomy and determining the feasibility of revascularisation via PCI or CABG. It is the primary diagnostic and therapeutic pathway for patients presenting with STEMI and high-risk NSTEMI. In stable angina, it is typically reserved for patients whose symptoms are poorly controlled on medical therapy or those with high-risk features on non-invasive ischaemia testing.

A 'normal' luminogram does not exclude microvascular angina or vasospastic (Prinzmetal) angina. Overlying structures or foreshortening of vessels in certain views can lead to the 'misdiagnosis' of a stenosis; hence, multiple angles are mandatory. Clinicians must ensure the patient is sufficiently hydrated and that renal function has been Checked (eGFR) prior to the use of iodinated contrast.

Angiography is a two-dimensional 'luminogram' and may underestimate the total plaque burden within the vessel wall. It carries procedural risks including vascular access complications (haematoma, pseudoaneurysm), contrast-induced nephropathy, and rare but serious risks of stroke, myocardial infarction, or coronary artery dissection. It is less effective at evaluating the microcirculation compared to epicardial vessels.

Students must understand the indications for 'primary PCI' versus 'elective' angiography. Recognition of the major coronary arteries (LAD, Circumflex, RCA) on angiographic views is a frequent OSCE and written exam requirement. Awareness of the 'radial-first' approach as the UK standard of care is essential.