Invasive Coronary Angiography: Indications and Vascular Access

Definition and Clinical Role

Invasive coronary angiography (ICA) is a catheter-based investigation that visualizes the coronary arterial tree after selective intracoronary contrast injection under fluoroscopy. The procedure is performed by advancing guidewires and diagnostic catheters from a percutaneous arterial access site to the aortic root, engaging the coronary ostia, and acquiring multiple angiographic projections.

Although traditionally regarded as an anatomical examination, contemporary ICA can provide complementary functional and structural information. Coronary pressure measurements permit assessment of the physiological significance of selected stenoses using fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR). Other invasive techniques can quantify coronary flow reserve (CFR), assess microvascular resistance, and investigate coronary vasospasm. Intravascular ultrasound (IVUS) and optical coherence tomography (OCT) provide cross-sectional information about plaque morphology and may clarify the mechanism of an acute coronary syndrome or guide percutaneous coronary intervention (PCI).

ICA therefore has three principal roles:

• Defining the anatomical distribution and severity of epicardial coronary artery disease (CAD).

• Assessing the haemodynamic significance of lesions whose angiographic severity is uncertain.

• Supporting decisions regarding revascularization and, in selected patients, identifying microvascular or vasomotor coronary disorders.

The investigation should be undertaken when its diagnostic or therapeutic consequences are likely to outweigh procedural risks. This balance forms part of shared clinical decision-making.

Pathophysiological and Diagnostic Considerations

Angiographic severity and physiological severity do not always correspond. Visual estimation of luminal narrowing may therefore be insufficient when deciding whether an intermediate lesion should be revascularized. Coronary pressure assessment is consequently recommended to complement ICA, particularly for intermediate non-left-main coronary stenoses.

Myocardial ischaemia may occur despite the absence of significant epicardial obstruction. In patients with anginal symptoms and unobstructed or non-obstructive coronary arteries, possible mechanisms include microvascular obstruction, endothelial dysfunction and epicardial coronary spasm. The absence of obstructive CAD on ICA should therefore not automatically be interpreted as evidence that the patient’s symptoms are non-cardiac.

In acute coronary syndrome (ACS), the angiographic culprit lesion may appear as an eccentric stenosis with scalloped or overhanging margins and a narrow neck. These findings may reflect plaque disruption or thrombus. A rounded or polypoid intraluminal mass and lesion haziness raise suspicion of thrombus, although haziness is not specific.

Intravascular imaging can identify plaque disruption, thrombus and other structural features that may not be evident on angiography alone. It is particularly useful when ACS occurs without significant obstructive CAD or when more than one potential culprit lesion is present.

Clinical Indications

Suspected Chronic Coronary Syndrome

The decision to perform ICA is based on the clinical likelihood of obstructive CAD, symptoms, findings from non-invasive testing and the anticipated effect of the result on management.

ICA with available coronary pressure assessment is recommended in patients with a very high clinical likelihood of obstructive CAD, defined in the source material as greater than 85%, particularly when one or more of the following are present:

• Severe symptoms despite guideline-directed antianginal treatment.

• Typical angina or dyspnoea at a low level of exertion.

• Left ventricular dysfunction suggesting extensive obstructive CAD.

• A high-risk result on non-invasive testing.

• Symptoms that are strongly suggestive of obstructive CAD.

• Uncertain or inconclusive non-invasive test results, when confirmation or exclusion of obstructive CAD is clinically important.

In patients with newly developed symptoms that are highly suggestive of obstructive CAD and occur at a low level of exercise, ICA with a view to possible revascularization may be used as the first diagnostic test after cardiological assessment.

Non-invasive findings that support ICA include:

• CCTA showing at least 50% left main coronary stenosis.

• At least 70% proximal left anterior descending artery stenosis in the setting of single- or two-vessel CAD.

• More than 70% proximal three-vessel disease.

• Moderate-to-severe inducible ischaemia on stress testing.

In these circumstances, ICA and coronary pressure assessment are used for additional risk stratification and to determine whether revascularization is appropriate.

Suspected ANOCA or INOCA

In patients with suspected angina or ischaemia with non-obstructive coronary arteries, ICA may demonstrate no significant epicardial CAD or only intermediate lesions with normal FFR or iFR. When symptoms persist despite medical treatment, quality of life is poor and the diagnosis remains clinically relevant, invasive coronary functional testing is recommended to identify potentially treatable endotypes.

This assessment may include:

• Index of microcirculatory resistance (IMR).

• CFR.

• Invasive vasoreactivity testing with acetylcholine or ergonovine when indicated.

Acute Coronary Syndrome

Invasive management is time-sensitive in ACS.

Patients with a high suspicion of ongoing coronary artery occlusion, including persistent ST-segment elevation or equivalent findings, should undergo emergency angiography as soon as possible when triaged to an immediate invasive strategy.

In high-risk NSTE-ACS, an early invasive strategy means angiography within 24 hours. High-risk features include:

• NSTEMI confirmed using the 0 h/1 h or 0 h/2 h diagnostic algorithms.

• Dynamic ST-segment or T-wave changes.

• Transient ST-segment elevation.

• A GRACE risk score greater than 140.

An early invasive approach is favoured over a selective invasive strategy in NSTE-ACS patients with ST-segment changes or a positive troponin assay at presentation, or when these features develop during the subsequent 24 hours, provided there is no contraindication and the coronary anatomy is suitable.

The early invasive approach is not recommended when extensive comorbidity makes the risks of revascularization greater than its likely benefit, or in patients with acute chest pain whose clinical likelihood of ACS is low and whose troponin assay is negative.

Before Valve Intervention or Surgery

Coronary anatomy should be assessed when valve surgery or an intervention is planned, so that the information is available for Heart Team deliberation.

In patients with a low or moderate pre-test likelihood of obstructive CAD, defined as 50% or less, CCTA is recommended to exclude relevant CAD with high sensitivity. In patients with a high or very high pre-test likelihood, invasive coronary angiography is recommended before valve intervention.

For patients undergoing surgery for infective endocarditis:

• ICA is recommended in patients at high risk for CAD when aortic valve vegetations are absent.

• In haemodynamically stable patients with aortic valve vegetations who require surgery and have high CAD risk, high-resolution multislice coronary CTA is recommended.

• ICA may be considered selectively despite aortic valve vegetations in patients with known CAD or a high likelihood of significant obstructive CAD.

• In emergency circumstances, valve surgery without pre-operative coronary anatomy assessment may be considered regardless of CAD risk.

The presence of aortic valve vegetations may increase concern about iatrogenic embolization during invasive angiography. Conversely, emergencies may preclude detailed pre-operative coronary assessment.

Patients Undergoing TAVI

In TAVI candidates, omission of ICA should be considered when the procedural planning CT angiography is of sufficient quality to exclude significant CAD. This is particularly relevant because severe aortic stenosis, extensive coronary calcification and atrial fibrillation may impair the specificity and interpretability of CCTA.

In patients with a primary indication for TAVI:

• PCI should be considered for coronary stenosis of at least 90% in a vessel with a reference diameter of at least 2.5 mm.

• PCI may be considered for stenosis of at least 70% in a proximal segment of a major coronary vessel, based partly on symptoms.

The timing of PCI remains individualized and should account for coronary lesion complexity, valve design and the expected difficulty of coronary access after TAVI.

Patients With Valvular Heart Disease

Coronary pressure measurements and FFR may be altered by concomitant valvular heart disease. Functional haemodynamic assessment is not well established in this setting, and interpretation requires caution, particularly in severe aortic stenosis.

For patients with a primary indication for valve surgery:

• CABG is recommended when coronary stenosis is at least 70%.

• CABG should be considered when stenosis is between 50% and 70%.

In severe ventricular secondary mitral regurgitation, ICA is recommended as part of CAD assessment.

Pre-Procedural Clinical Assessment

Selection for ICA should integrate:

• Clinical presentation and symptom burden.

• The estimated pre-test likelihood of obstructive CAD.

• Electrocardiographic findings.

• Echocardiographic assessment, including left ventricular function.

• Blood-test results.

• Stress-test findings.

• CCTA or MRCA findings when performed.

• The potential for revascularization or a change in medical management.

The anticipated procedural consequence is important. ICA is most informative when the findings will guide revascularization, refine risk stratification or clarify an uncertain diagnosis.

The patient should be informed in advance of the potential benefits, procedural risks and possible therapeutic consequences. This is particularly important because ICA is invasive and may lead to PCI, CABG or continued medical therapy depending on the coronary anatomy and physiological findings.

Technical Procedure

ICA is performed using the Seldinger technique. After insertion of a valved sheath into a percutaneous arterial access site, a flexible J-tipped guidewire is advanced under fluoroscopy toward the aortic root. A diagnostic catheter is then passed over the wire. Once the catheter reaches the aortic root, the guidewire is removed, the catheter is flushed and connected to the contrast injection system.

Under fluoroscopic guidance, the catheter tip is selectively positioned at the coronary ostium. Small contrast injections are delivered into the coronary artery while the x-ray system is positioned to obtain appropriate projections. Multiple views are used to characterize the coronary arterial tree and reduce the possibility that a lesion is underestimated because of vessel overlap or foreshortening.

Vascular Access

Radial Access

Radial arterial access is the preferred route when ICA is indicated. Guideline recommendations support radial access with the highest stated recommendation category and level of evidence in the source material.

Its principal advantages include:

• Lower major bleeding risk than femoral diagnostic catheterization.

• Lower mortality.

• Earlier mobilization.

• Rapid ambulation after the procedure.

Radial access should therefore be used whenever feasible, while accounting for the patient’s vascular anatomy and the technical requirements of the procedure.

Femoral Access

Femoral diagnostic catheterization has been associated with a composite major complication rate of approximately 0.5%–2.0%, with bleeding requiring transfusion forming the principal component of these complications. Although femoral access remains relevant in selected circumstances, the reduction in bleeding and mortality associated with radial access has made the radial route standard whenever possible.

Angiographic and Physiological Assessment

Coronary Angiography

ICA provides direct anatomical information about:

• The presence or absence of epicardial CAD.

• The distribution of disease.

• The number of affected vessels.

• The location and apparent severity of stenoses.

• Potential culprit lesions in ACS.

• Coronary anatomy relevant to PCI or CABG.

The angiographic estimate alone may not define whether a lesion limits coronary blood flow. This is particularly important for intermediate stenoses, for which physiological assessment should be readily available.

FFR and iFR

FFR and iFR are invasive coronary pressure-based techniques used to determine the functional significance of coronary stenoses. They are recommended for assessment of intermediate non-left-main lesions before revascularization.

For intermediate left-main stenoses, measurement of FFR or iFR should be considered before revascularization. IVUS should also be considered for evaluating the severity of intermediate left-main stenosis.

Coronary Flow and Microvascular Assessment

Contemporary invasive assessment can measure:

• CFR.

• Microvascular resistance, including IMR.

• Vasomotor responses during invasive vasoreactivity testing.

In suspected ANOCA or INOCA, these measurements can help identify microvascular dysfunction or vasospastic disease and select a potentially treatable mechanism.

Intravascular Imaging

IVUS and OCT

IVUS and OCT are invasive cross-sectional imaging modalities that characterize plaque morphology. They are most frequently used to guide and optimize coronary stent implantation, but they also have diagnostic value.

In ACS patients without significant obstructive CAD on angiography, intravascular imaging may help exclude an atherothrombotic mechanism in the major coronary arteries. This distinction can affect immediate invasive management and decisions about prolonged antithrombotic treatment.

Intravascular imaging is also useful when the culprit lesion is uncertain. Ambiguity may occur when several lesions could account for the clinical syndrome.

For ACS with a clearly identified culprit lesion suitable for PCI, intravascular imaging—particularly IVUS in the evidence summarized—has a role in guiding the intervention. When the culprit is ambiguous, imaging, with OCT preferred in the guideline summary, may assist diagnosis and treatment selection, although the recommendation is less strong.

Intravascular Imaging in SCAD

In suspected spontaneous coronary artery dissection, OCT or IVUS should be used cautiously when angiography leaves genuine diagnostic uncertainty. Coronary instrumentation may itself increase risk, particularly in tortuous vessels, small-calibre arteries or distal lesions. Before advancing an imaging catheter, the guidewire must be confirmed to lie in the true lumen.

When angiography establishes SCAD and the intended strategy is medical therapy, additional coronary instrumentation and intravascular imaging are not recommended on safety grounds.

Physical Examination and Electrocardiography

The source material emphasizes clinical presentation, pre-test likelihood and integration of ECG into the diagnostic pathway, but it does not provide a detailed physical-examination protocol or a comprehensive description of ECG findings for routine ICA selection.

In suspected vasospastic angina, a resting 12-lead ECG obtained during an episode of angina is recommended. Repetitive rest angina accompanied by transient ST-segment changes that resolve with nitrates or calcium antagonists supports the need for invasive functional angiography to confirm the diagnosis and evaluate underlying atherosclerotic disease.

Laboratory Findings and Biomarkers

Troponin measurement is central to the invasive strategy in NSTE-ACS. Patients ruled in as NSTEMI using the 0 h/1 h or 0 h/2 h algorithms are regarded as high-risk candidates for early angiography within 24 hours.

Conversely, an early invasive strategy is not recommended for patients with acute chest pain, a low clinical likelihood of ACS and a negative troponin assay.

The source material does not provide a broader laboratory evaluation, specific troponin thresholds or additional biomarker recommendations.

Management After Angiography

ICA may be followed by one of three broad management pathways:

• PCI, when the anatomy and clinical context are appropriate.

• CABG, when surgical revascularization is indicated.

• Continued medical therapy, when revascularization is not indicated or its risks outweigh its expected benefit.

The decision should incorporate the anatomical findings, physiological lesion assessment, symptoms, ventricular function, comorbidities, procedural risk and the anticipated benefit of revascularization.

In NSTE-ACS, an invasive strategy reduces cardiovascular composite outcomes and hospital length of stay compared with a delayed or selective strategy, although the summarized evidence does not demonstrate a mortality reduction with the early invasive approach. Over longer follow-up, differences between early invasive and selective strategies may diminish because patients initially managed selectively subsequently undergo revascularization.

Drug Therapy

The source material gives a specific pharmacological recommendation for vasospastic angina:

• Calcium-channel blockers are recommended for isolated vasospastic angina to control symptoms, prevent ischaemia and reduce potentially fatal complications.

No drug doses or broader antianginal, antithrombotic or secondary-prevention regimens are specified in the source material. Accordingly, specific doses and additional drug strategies are not detailed here.

Guideline-Based Recommendations

Procedural Risk and Safety

ICA is associated with a small but clinically important risk of major complications. The composite risk of death, myocardial infarction or stroke with radial access is approximately 0.1%–0.2% in the summarized guideline material. Femoral diagnostic catheterization carries a higher reported composite rate of major complications, approximately 0.5%–2.0%, predominantly because of bleeding requiring transfusion.

Risk assessment should therefore consider:

• The likelihood that angiography will alter management.

• The probability of significant obstructive CAD.

• The feasibility and expected benefit of revascularization.

• Bleeding and vascular-access risk.

• Comorbidities and procedural risk.

• The urgency of the clinical presentation.

Prognosis and Follow-Up

Prognosis after ICA depends primarily on the underlying coronary anatomy, the presence or absence of obstructive disease, ventricular function, the physiological significance of lesions and the selected management strategy.

Patients with non-obstructive coronary findings may still have clinically important ischaemia related to microvascular dysfunction or coronary spasm. Identification of these endotypes through invasive functional testing may improve symptoms and quality of life by permitting more targeted treatment.

In ACS, early invasive management reduces cardiovascular composite outcomes and hospital stay, although the summarized data do not demonstrate a mortality reduction compared with a delayed or selective strategy. Longer-term differences may become less apparent because patients initially managed selectively may later undergo revascularization.

Follow-up should be directed by the final diagnosis and treatment pathway, including:

• Review of symptoms and functional status.

• Assessment of response to medical therapy.

• Evaluation after PCI or CABG when performed.

• Ongoing management of identified vasospastic or microvascular disease.

• Reassessment when symptoms persist despite apparently non-obstructive coronary anatomy.

The source material does not specify a uniform post-angiography surveillance schedule or detailed long-term medication regimen.