Definition
Coronary angiography uses radio-opaque contrast agent to delineate the anatomy of the coronary circulation. This may be performed either invasively using specially designed intra-arterial catheters or non-invasively by computerised tomography (CT) imaging. This chapter will focus on invasive coronary angiography and its role in current clinical practice.
Historical Perspective
The Nobel Laureate Werner Forssmann is credited with the first cardiac catheterisation in 1929 although this was exclusively right heart catheterisation via the left antecubital vein. Various reports of non-selective coronary angiography in human subjects followed in the 1940s and 1950s, culminating in the first selective (albeit serendipitous) coronary angiogram performed in 1958 by Frank Mason Sones in his basement laboratory at the Cleveland Clinic. Melvin P Judkins and Kurt Amplatz made significant modifications to the technique in the 1960s. They designed catheters specifically for selective coronary cannulation, developing J-tipped guidewires that were introduced via the catheter lumen, and popularised the Seldinger technique of percutaneous arterial access via the femoral route. Eponymously named catheters designed by Judkins and Amplatz are still routinely used for coronary angiography today.
Indications
Invasive coronary angiography remains the gold standard investigation for the assessment of coronary anatomy. The indications for coronary angiography in the assessment of ischaemic heart disease are described in detail in joint ESC, ACCF, ACC and AHA guidelines for the diagnosis and management of patients with stable ischaemic heart disease, acute coronary syndromes including STEMI, heart failure, sudden cardiac death, valvular heart disease, preoperative evaluation for non-cardiac surgery and major organ transplantation. These are summarised in Table 4.1. A detailed report listing the appropriate use criteria for coronary angiography was published in 2012. Appropriate use of invasive coronary angiography to investigate stable angina is also discussed in section 1.5 of the NICE guidance on the management of stable angina.
Table 4.1 Indications for invasive coronary angiography
| Indicated | Rationale |
|---|---|
| ACS (STEMI/NSTEMI/UA) | High pretest probability of CAD and/or symptoms despite two antianginal medications and/or a positive non-invasive function test and/or in cases where revascularisation may improve prognosis |
| Stable CAD | |
| Prior to non-cardiac surgery | |
| Pretransplant assessment | |
| New diagnosis of heart failure | To delineate coronary anatomy and rule out or confirm significant CAD |
| Survivor following sudden cardiac death/ventricular arrhythmia | |
| Prior to heart value surgery | If age >35 years or postmenopausal at any age |
| Not indicated | |
| Preoperative evaluation | ‘Routine’ angiography in the absence of clinical suspicion or where non-invasive tests indicate low pretest probability |
| Pretransplant | |
Preprocedural Assessment
Route of Arterial Access
The latest available annual report of the British Coronary Interventional Society indicates a steady increase in the use of radial access and a corresponding decline in femoral access for percutaneous coronary intervention (PCI). Diagnostic angiography has also followed a similar trend over the last decade. With multiple clinical trials suggesting a net reduction in adverse clinical events with radial access for PCI, this trend is likely to continue.
Assessment of the peripheral arterial supply is important before deciding the route of access for invasive coronary angiography. Symptomatic lower limb peripheral arterial disease, abdominal aortic aneurysms with thrombus in situ or previous vascular surgery (peripheral arterial bypass and/or grafts) may preclude a femoral approach although femoral access can be gained if necessary through Gore-Tex™ grafts. Increasingly, radial arterial access is utilised, as the hand has a dual arterial blood supply. Confirmation of ulnar artery patency (and/or radial artery patency in patients that have had this artery cannulated previously) is recommended by performing a modified Allen’s (or reverse Allen’s) test, plethysmography or pulse oximetry.
Angiography of coronary artery bypass graft conduits is traditionally performed from a femoral arterial access although the left radial artery is also an appropriate route of access for left internal mammary grafts. In patients awaiting assessment for haemodialysis, it is prudent to avoid radial access as this is a commonly used site for arteriovenous fistulae.
History of Adverse Reaction/Allergy
Any prior history of allergy to contrast agents is an important consideration. The onset and severity of the reaction should be explored as well as the indication for invasive coronary angiography before deciding whether further contrast exposure is justified. Although a history of seafood allergy is often documented, there is no evidence to suggest that this increases the likelihood of adverse reaction to iodinated contrast media. The risk of a serious allergic reaction is reported as 0.02–0.5%. It is routine practice to administer systemic steroids several hours before the procedure and antihistamines 1–2 hours prior to angiography in patients with a history of suspected or confirmed adverse reactions.
Consent
Written informed consent by a competent operator following discussion of potential complications is mandatory prior to the procedure (see Complications section).
Access Site Preparation
The area of skin around the access site (radial artery or femoral artery) may need to be prepared according to standard aseptic surgical practice.
Premedication
An anxiolytic is useful in allaying anxiety and to avoid spasm of the radial artery. This is usually achieved by appropriately timed oral or parenteral benzodiazepines after consent has been obtained.
Prehydration
Acute kidney injury is rare following diagnostic coronary angiography, which typically uses <100 ml of contrast agent. Contrast induced nephropathy (CIN) is a form of acute kidney injury following administration of an iodinated contrast agent and is usually reversible. A 25% rise in serum creatinine levels from baseline at 48 hours after administration of the contrast agent is often set as a threshold for diagnosis of CIN in clinical trials. International guidelines recommend the use of isoosmolar contrast agents to reduce the risk of CIN. Prehydration with isotonic saline has been shown to be effective in preventing CIN especially in women, diabetics and in those requiring high volumes of contrast agent (>250 ml). Trials comparing intravenous saline versus bicarbonate prehydration have failed to demonstrate any advantage of one agent over the other. We recommend the use of 0.9% saline for periprocedural hydration in patients at risk of CIN. Patients are encouraged to drink clear fluids freely in the periprocedural period. A risk score based on eight clinical variables proposed by Mehran et al. more than a decade ago has been validated in a recent study as a reliable tool in predicting the risk of CIN in ACS patients undergoing coronary angiography.
Anticoagulation
A careful review of the indication for anticoagulation and the risk of thrombosis from interruption of anticoagulant therapy should be made in all cases. In an elective setting the anticoagulant is temporarily suspended where possible, although coronary angiography may be performed via the radial route in anticoagulated patients if necessary. Such cases should be discussed with the operator and planned on an individual patient basis. A meta-analysis of studies that compared uninterrupted anticoagulation with interruption ± heparin bridging suggests that coronary angiography may be safely performed by continuing warfarin therapy with a target INR of 2.0–2.5.
Antiplatelet Agents
There is no reason to discontinue antiplatelet therapy prior to diagnostic angiography. In instances where angiography may proceed to PCI it is mandatory to treat the patient with loading doses of antiplatelets according to local protocols.
Many of these preprocedural checks are confirmed with a World Health Organisation (WHO) surgical check list.
Coronary Angiography
Image Acquisition, Analysis and Interpretation
Invasive coronary angiography is an accurate imaging modality to delineate luminal anatomy although, unlike non-invasive CTCA, it cannot comment on the arterial wall. Multiple views (projections) are acquired by radiography by injecting iodinated contrast into the coronary arteries whilst being mindful of minimising contrast and radiation exposure to the patient, as a stenosis in the ‘lumenogram’ may be eccentric or foreshortened and could otherwise be missed. This is especially true in bifurcation lesions.
The right and left coronary arteries arise from the corresponding coronary sinuses immediately above the aortic valve. The right coronary artery runs in the right atrioventricular (AV) groove until the crux (the anatomical intersection of the right and left AV grooves and the posterior interventricular groove). Along its course the RCA supplies the sinoatrial and atrioventricular nodes, the right atrium and right ventricle and frequently the inferoposterior wall of the left ventricle as it enters the posterior interventricular groove as the posterior descending artery (PDA) in over 80% of cases. This is referred to as a right dominant circulation.
The left main coronary artery (LMCA) runs a short course (usually 5–10mm) before bifurcating into the left anterior descending artery (LAD) that runs in the anterior interventricular groove and the left circumflex artery (LCx) which mirrors the course of the right coronary artery in the left AV groove. The LAD supplies most of the interventricular septum through its septal perforating branches and the anterolateral wall of the left ventricle from two or more diagonal branches. Obtuse marginal branches arise from the LCx and supply the posterolateral LV myocardium. In 10% of cases the LCx continues as the PDA (left dominant circulation) in the posterior interventricular groove, while in the remaining 10% of cases both the RCA and the LCx provide branches to the posterior interventricular groove (codominant circulation). Typical coronary angiographic images are represented in Figure 4.1.
