CardiologyTier 2Topic

Coronary angiography

What it is

Invasive contrast imaging of the coronary arteries, the reference standard for coronary anatomy
Access: radial (default in Australia) > femoral
- Radial: lower bleeding, lower mortality in ACS (MATRIX/RIVAL), earlier ambulation. Femoral for large-bore devices, IABP, structural work
Standard views: LAO/RAO with cranial/caudal angulation to open bifurcations
- "Spider" view (LAO caudal) - left main bifurcation
Left ventriculography (RAO 30) for EF and MR if echo inadequate

Gives a luminogram - the silhouette of the lumen, not the vessel wall
- Glagov positive remodelling means a plaque can be large with a preserved lumen -> angiographically "normal"
Anatomical, not physiological - a 50-70% stenosis by eye may or may not cause ischaemia
- -> physiological assessment (FFR/iFR) or intravascular imaging closes the gap

Inter-observer variability in visual stenosis grading is substantial (~20% absolute)
Roughly 1 in 3 intermediate lesions judged significant by eye are not significant on FFR (and vice versa)
INOCA / ANOCA - ischaemia or angina with non-obstructive coronaries in up to 50% of women and 30% of men undergoing angiography for angina

Right dominant ~85% (PDA from RCA), left dominant ~8%, co-dominant ~7%
SA nodal artery: RCA 60%; AV nodal artery: RCA 90% -> inferior MI causes AV block

Left main disease - highest risk; historically surgical
Proximal LAD - large territory
Bifurcation, calcification, tortuosity, chronic total occlusion (CTO) - raise procedural complexity
Thrombus grade, plaque rupture vs erosion
SYNTAX score - anatomical complexity; guides PCI vs CABG in multivessel and left main disease

FFR = pressure distal to the lesion / aortic pressure, at maximal hyperaemia (IV or IC adenosine)
- FFR <=0.80 = haemodynamically significant (a pressure drop of more than 20% across the lesion)
- FAME/FAME-2: FFR-guided PCI reduces stents, events and cost vs angiography alone
- Unreliable where microvascular disease blunts hyperaemia - severe LVH, recent MI, ostial lesions, severe AS
iFR / RFR / dPR (non-hyperaemic indices) - cutoff <=0.89, no adenosine needed; non-inferior to FFR (DEFINE-FLAIR, iFR-SWEDEHEART)
CFR (coronary flow reserve) <2.0 and IMR (index of microcirculatory resistance) >25 -> microvascular dysfunction
Acetylcholine provocation -> epicardial spasm (vasospastic angina) vs microvascular spasm

Grade	Flow
0	No antegrade flow beyond the occlusion
1	Faint antegrade flow, incomplete distal filling
2	Complete distal filling but delayed
3	Normal flow, complete prompt distal filling

TIMI 3 flow post-PCI is the procedural goal and predicts outcome
TIMI myocardial blush grade 0-3 - tissue-level (microvascular) reperfusion; TIMI 3 epicardial flow with blush 0 = no-reflow**

	IVUS	OCT
Modality	Ultrasound	Near-infrared light
Penetration	Deeper - good for left main, ostia, vessel wall	Shallow
Resolution	~100 um	~10 um - best for thrombus, dissection, stent apposition, plaque erosion
Contrast needed	No	Yes (caution in CKD)

Imaging-guided PCI reduces target-lesion failure and stent thrombosis vs angiography alone in complex lesions (ILUMIEN IV, OCTOBER, RENOVATE-COMPLEX-PCI) - now a guideline recommendation for complex PCI
Essential in MINOCA work-up: identifies plaque erosion, SCAD, spontaneous thrombus

A. Indications

STEMI - primary PCI (target door-to-balloon <90 min)
NSTEACS - invasive strategy, timing by risk (<2 h if very high risk: haemodynamic instability, refractory angina, life-threatening arrhythmia, mechanical complication; <24 h if high risk: GRACE >140, dynamic ST/T changes, rise/fall in troponin)
Stable angina - refractory to medical therapy, high-risk non-invasive test, or high-risk anatomy on CTCA
Pre-operative assessment for valve surgery
Unexplained ventricular arrhythmia, new cardiomyopathy of uncertain cause, out-of-hospital cardiac arrest
MINOCA work-up
Note: ISCHEMIA showed no mortality benefit from routine revascularisation over optimal medical therapy in stable moderate-severe ischaemia without left main disease - symptoms are the main driver in stable disease

B. Preparation

Consent for angiography and possible PCI; explain radiation and contrast
Renal function, hydration in CKD (isotonic saline pre/post; minimise contrast volume)
Metformin - withhold on the day and for 48 h after if eGFR <30 or contrast nephropathy risk
Continue aspirin; antiplatelet loading per protocol; anticoagulant management per access and indication
Allergy history (contrast, shellfish myth - iodine allergy is not a thing; prior contrast reaction matters)

C. Revascularisation decision

Heart Team for left main, multivessel, complex anatomy, diabetes
CABG favoured: left main with high SYNTAX, three-vessel disease especially with diabetes (FREEDOM), LV dysfunction (STICH)
PCI favoured: single/two-vessel, low SYNTAX, high surgical risk, ACS culprit
Complete vs culprit-only revascularisation in STEMI: staged complete revascularisation is superior (COMPLETE)

D. Post-procedure

	Rate
Death (diagnostic)	~0.1%
MI, stroke	~0.1-0.2% each
Access site (haematoma, pseudoaneurysm, AV fistula, radial occlusion)	1-5% (femoral > radial)
Contrast-associated AKI	1-5%, higher with CKD + diabetes
Arrhythmia (VF on injection)	<1%
Coronary dissection / perforation	~0.2%
Cholesterol embolisation	Rare - livedo, blue toe, eosinophilia, renal failure
Retroperitoneal haemorrhage (femoral)	~0.5% - unexplained hypotension post-femoral access
Contrast anaphylactoid reaction	<1%

Radiation - operator and patient dose; skin injury in prolonged CTO cases
No-reflow - microvascular obstruction despite a patent epicardial vessel
Stent thrombosis (acute, subacute, late, very late) vs in-stent restenosis (neointimal hyperplasia, months-years, presents as recurrent angina not ACS)

CTCA - excellent negative predictive value; first-line for low-intermediate pre-test probability stable chest pain. Adds FFR-CT and plaque characterisation. Poor with heavy calcification, stents, high/irregular heart rate
Functional imaging (stress echo, MPI, stress CMR) - detects ischaemia; better for intermediate lesions and known CAD
Invasive angiography - reserved for high pre-test probability, ACS, or when revascularisation is intended

1. Does this patient have coronary disease? -> CTCA

2. Is the lesion causing ischaemia? -> FFR/iFR or functional imaging

3. Will revascularising it help? -> symptoms, territory at risk, LV function, ISCHEMIA/COMPLETE data

4. PCI or CABG? -> SYNTAX, diabetes, LV function, Heart Team

Treating an angiographic stenosis without establishing ischaemia is the classic error - the "oculostenotic reflex"

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