34
Angiographic Views: Coronary Arteries and Grafts, Left Ventricle, Aorta, Coronary Anomalies, Peripheral Arteries, Carotid Arteries

I. Right coronary artery

A. Course

The right coronary artery (RCA) courses over the right AV groove, turns around and continues over the posterior AV groove, then reaches the intersection of the AV groove and the posterior interventricular groove (designated the crux), where it gives the PDA and PLB branches.

B. Branches (proximally to distally) (Figure 34.1)

Conus branch (CB) is the first RCA branch. It supplies the RVOT and has a separate ostium in 50% of individuals.
Sinus node branch (SN) originates from the RCA in 60% of individuals and from the LCx in 40%.
Acute marginal branches (AM) supply the RV (1–3 branches).
Posterior descending artery (PDA) runs on the posterior interventricular groove and supplies inferior septal branches to the inferior 25–30% of the septum (known as “inferior wall”). PDA runs parallel to the LAD, which supplies the anterior 70–75% of the septum.
Posterolateral branches (PLBs) originate from the posterior AV groove past the crux and supply the posterior wall. This part of the RCA gives rise to the AV nodal branch.

C. Segments of the RCA

Proximal RCA: RCA before the AM branches.
Mid-RCA: RCA around the AM branches.
Distal RCA: RCA past the AM branches, including distal RCA at the level of the crux, PDA, and PLBs.

Figure 34.1 RCA course and branches. The intersection of the AV groove and the inferior septum is the crux.

Figure 34.2 (a) Left coronary system on LAO cranial view. (b) LV walls on cross-sectional view of the LV.

II. Left coronary artery

A. Left main (LM) branches into the left anterior descending and left circumflex arteries

B. Left anterior descending artery (LAD) (see Figure 34.2)

LAD courses over the anterior interventricular groove, then reaches and frequently (80%) wraps around the apex distally. LAD gives: (i) diagonal (Dg) branches, usually 1–3 large diagonal branches which supply the anterior and high lateral walls; and (ii) septal branches which supply the anterior septum, i.e., ~70–75% of the thickness of the septum. The inferior septum is supplied by the PDA, which runs parallel to the LAD. Some patients have a dual LAD system, in which one trunk (frequently intramyocardial) gives all the septal branches and another trunk gives all the diagonal branches.
Segments
- Proximal LAD = LAD proximal to the first septal branch (which is often, but not always, proximal to the first diagonal branch)
- Mid LAD = LAD around all the major diagonal branches
- Distal LAD = LAD distal to the major diagonal branches

C. Left circumflex coronary artery (LCx) (see Figure 34.2)

LCx courses over the left AV groove (like the RCA on the opposite side). It does not usually reach the crux, unless the left system is dominant.
Branches
1. One to several obtuse marginal (OM) branches supply the LV free lateral wall.
2. One or more left PLBs arise from the left AV groove before the crux. These left PLBs are adjacent to the right PLBs.
3. PDA branch may arise from the distal LCx at the crux level in a dominant or co-dominant left system.

D. Ramus intermedius (RI) branch

Sometimes, the left main (LM) trifurcates into LAD, RI, and LCx (instead of bifurcating into LAD and LCx). RI is, in a way, a very proximal diagonal or a very proximal OM, and supplies the anterolateral wall.

Dominance refers to which artery, RCA or LCx, gives the PDA (inferior wall) and the PLB branches (posterior wall).

RCA dominance (85% of the population): RCA gives both the PDA and the PLBs. LCx gives only the OM branches and may give some, but not all, PLBs. LCx does not reach the crux.
Left dominance (8% of the population): LCx gives both the PDA and the PLBs. In this case, RCA is small and does not reach the crux.
Co-dominance (7% of the population): RCA gives the PDA while LCx gives all of the PLBs and sometimes a second, parallel PDA.

At or near the crux, the dominant artery gives rise to the AV nodal branch.

In ~25% of patients with RCA dominance, there are significant anatomic variations in the origin of the PDA: double PDA, early origin of the PDA proximal to the crux, or partial supply of the PDA territory by a low AM branch that wraps around the inferior RV wall and reaches the inferior septum (streaker branch). Also, the inferior wall may be partially supplied by a long wraparound LAD or by OM branches that wrap around the posterior wall.

III. Coronary angiography views. Recognize the angle of a view: LAO vs. RAO, cranial vs. caudal

A. Differentiate left anterior oblique (LAO) from right anterior oblique (RAO) views

Look at the spine or the central catheter in the descending aorta (if femoral access), then see whether the tip of the catheter is at its left (LAO) or right (RAO). For example, in the LAO view, one “grabs” the catheter tip with the left hand while “grabbing” the central aortic catheter (or spine) with the right hand (Figure 34.4). If the catheter tip overlaps with the central catheter or the spine, it is an anteroposterior (AP) view or a shallow-angled view. Other technique: look at the ribs, and see if they are going down toward your left hand (LAO) or right hand (RAO).

B. Differentiate cranial from caudal views

In cranial views, the dome of the diaphragm is seen over the heart shadow (Figure 34.5).

IV. Coronary angiography views. General ideas: cranial vs. caudal views

Caudal views properly assess the distal LM bifurcation, proximal LAD, and the whole LCx. The mid and distal LAD segments are usually foreshortened and overlapped with the Dg branches.
Cranial views properly assess the mid and distal LAD, diagonal branches, and septal branches. Cranial views are usually good views for the ostial LM, but are often inadequate for the LM bifurcation area (distal LM and proximal LAD and LCx) (Figure 34.6).

Figure 34.3 The top two rows show the difference in morphology between stable stenoses (usually smooth), unstable stenoses, and thrombus.

The bottom row shows hazy lesions. A hazy lesion could be an eccentric stenosis with no angiographic view orthogonal to the narrow lumen (a and b, arrows are angiographic angles). The narrow lumen is white and falsely projects as a large lumen at all angles. A hazy lesion could also be (c) a ruptured plaque, or (d) a lesion surrounded by a concentric shell of calcium. It often implies severe or unstable stenosis.

Figure 34.4 LAO view, cranial. Note the diaphragm overlapping with the heart shadow, and note the catheter tip at the left of the central aortic catheter/spine.

Figure 34.5 Shallow RAO view, cranial. Note the diaphragm overlapping with the heart shadow and the catheter tip slightly to the right of the central catheter in the descending aorta (the catheter tip is grabbed with the right hand, while the central catheter is grabbed with the left hand). Also, if the ribs are looking down towards the right-hand side of the operator, the view is RAO.

Figure 34.6 Illustration of the difference between caudal and cranial views. Caudal views show well the LM bifurcation into the LAD and LCx, as well as the LCx. Cranial views pull the LCx up and do not properly show the LM bifurcation and the proximal LAD–LCx area, but show the areas outside it (mid and distal LAD and ostial LM). The circles indicate the areas that are not well seen in each view.

Figure 34.7 View orthogonal to a segment vs. view foreshortening a segment.
In fact, on the caudal views, LCx is down, LAD is up; LAD and LCx are well separated, and their bifurcation off the LM is well visualized. On the cranial views, LCx moves up, along with the cranial angulation, and overlaps with the proximal LAD ± first diagonals; in addition to the overlap, the distal LM bifurcation and the proximal LAD are foreshortened. Yet, in patients with a vertical heart or a long LM, the caudal views may not open up the LM bifurcation properly; the cranial views may prove better for this purpose, particularly upon deep inspiration, which makes the heart even more vertical.

V. Coronary angiography views. General ideas: foreshortening and identifying branches

A. Foreshortening

A coronary segment is best assessed by a view orthogonal to it, i.e., a view that lays it out and fully expands it. Foreshortening implies looking at a coronary segment in line with its path, which, in two-dimensional imaging, condenses this segment and hides a stenosis by the contrast filling proximal and distal to it (Figure 34.7).

B. Arteries running on the border of the heart shadow

On any standard view, arteries that run on the border of the heart shadow, or are directed towards that border or touch it are usually diagonal or OM branches (depending on the view), not LAD.

VI. Left coronary views (see Figure 34.8)

A. RAO caudal (15° RAO, 25° caudal)

This is the best overall view and the best LCx view (Figures 34.9–34.12). In addition, it allows good assessment of the distal LM and the proximal LAD. The mid LAD is not well seen on this view as it is often foreshortened and overlapped with Dg branches that run above it and underneath it. The very distal apical LAD is usually well seen. If the ostial LCx overlaps with the distal LM, going more caudal will better separate the ostial LCx and the distal LM.

The RAO caudal view may be confusing when the LAD is totally occluded, in which case a large diagonal may simulate the LAD; a diagonal aims toward the heart border, whereas the LAD remains within the center of the heart shadow (Figure 34.13). In this instance, the cranial views further define whether the artery in question is LAD or Dg.

In patients with a tortuous or sharply angulated LCx, this view may foreshorten the proximal LCx, the proximal tortuosity, and even a proximal stenosis. This is reduced by deep inspiration (elongates the LCx). Also, AP caudal or LAO caudal complements this limitation of RAO caudal by showing the ostial/proximal angulation and tortuosity.

The AP caudal view often gives similar information to the RAO caudal view (Figure 34.14).

Schematic illustration of heart in an anteroposterior view. — **Figure 34.8** Heart in an anteroposterior view. Imagine how you look at the coronary arteries from various angles.

Schematic illustration of RAO caudal view (25°, 25°). — **Figure 34.9** **RAO caudal view** (25°, 25°).

Schematic illustration of RAO caudal view. — **Figure 34.10** **RAO caudal view.** Distal LM bifurcation area is well seen; if not, the view may be angled more caudally to pull the LCx down. The mid-LAD is foreshortened and overlapped with diagonal branches. The foreshortened area looks more dense, as it is “squashed.” The proximal LCx has a foreshortened area: this may be improved by imaging in deep inspiration, which straightens tortuosities.

Photo depicts RAO caudal view in a patient with a vertical heart. — **Figure 34.12** **RAO caudal view in a patient with a vertical heart.** Note that, in this particular case, even the LM bifurcation is not well opened. The distal LM, ostial LCx, and ostial LAD are overlapped (*left arrow*). This bifurcation may be opened by going more caudal; since the LCx follows the image intensifier, going more caudal pulls the LCx down and the LAD up, which opens up the bifurcation. In addition, the first diagonal is overlapped with the proximal/mid LAD (*right arrow*), which is expected in RAO caudal view.

Image described by caption. — **Figure 34.13** **(a)** RAO caudal with a large diagonal and a totally occluded LAD. The arrow points to a diagonal branch that simulates the LAD. The fact that it goes *out towards the heart border* implies that it is a diagonal branch rather than LAD, the LAD being totally occluded.

**(b)** LAO cranial of the same patient. LAO cranial shows the Dg going to the side, towards the heart border. No LAD is seen in the center of the heart shadow; the LAD is occluded past the diagonal and septal branches. Of note, the LAD usually runs parallel to the spine on this view (*dashed arrow*). This view confirms that the LAD is occluded when the RAO caudal view is suspicious.

Photo depicts AP caudal view. — **Figure 34.14** **AP caudal view.** Similarly to RAO caudal view, the AP caudal view shows the distal LM and the proximal LAD and LCx. The LM trifurcation is well visualized here. Note the foreshortening of the mid-LAD, wherein a large mid-LAD loop is looking towards the detector. The ramus reaches out towards the heart border, while the LAD remains inside the heart shadow.

B. LAO caudal (40° LAO, 30° caudal)

This view allows a good assessment of the LM, proximal LAD, proximal LCx, and proximal branches (Figure 34.15).

To obtain a good LAO caudal view, angle the image intensifier so that the tip of the catheter is positioned in the center of the cardiac silhouette. If it is not in the center of the cardiac silhouette, move the image intensifier more caudal or less LAO to obtain a good LAO caudal view, or instruct the patient to hold his breath in end-expiration, which makes the heart more horizontal.

This view looks at the heart from below and is best in patients with a horizontal heart, where the image intensifier can be almost perpendicular to the heart. This view may not properly open the LM bifurcation in patients with a vertical heart, and may be suboptimal in obese patients with a lot of soft tissue attenuation (may skip this view in those cases and rather obtain an AP caudal view). On the other hand, in patients with a vertical heart or a long LM, cranial views may allow better delineation of the distal LM and proximal and early mid-LAD than caudal views (Figures 34.16, 34.17, 34.18).

Schematic illustration of LAO caudal view (40°, 30°). — **Figure 34.15** **LAO caudal view** (40°, 30°). Catheter tip is at the center of heart shadow. LM is at the center, LAD is up, and LCx is down. OM and Dg are in the sector between LAD and LCx.

Photo depicts LAO caudal view of a vertical heart. — **Figure 34.16** **LAO caudal view of a vertical heart.** The catheter tip (*star*) is not in the center of the heart shadow (delineated by the *blue line*); hence, the distal LM bifurcation is not properly opened. The view needs to be angled more caudally or less LAO to center the catheter tip, or the view needs to be taken in deep expiration to make the heart horizontal. LAO caudal is difficult to optimize in patients with a vertical heart.

Photo depicts LAO caudal view of a horizontal heart. — **Figure 34.17** **LAO caudal view of a horizontal heart.** Note that the catheter tip is at the center of the cardiac silhouette, and the delineation of the LM bifurcation is excellent. 1, LAD; 2, LCx; 3, diagonal; 4, OM; x, LCx stenosis.

C. AP cranial or shallow RAO cranial (5° RAO, 35° cranial) (shallow RAO moves the left main away from the spine)

This view allows good assessment of the mid and distal LAD, as well as the diagonal and septal branches that originate from the mid and distal LAD and their points of bifurcation from the LAD. The distal LM, proximal LAD, proximal LCx, and the proximal branches are overlapped together and not well delineated (Figures 34.19, 34.20). Disease in the proximal portion of the LAD, LCx, ramus, or Dg may look like distal LM disease. Away from the LM bifurcation, the ostial LM is often well seen, as in most cranial views.

Sometimes, however, in patients with a vertical heart or a long LM, the distal LM bifurcation is well seen, especially with deep inspiration.

Schematic illustration of shallow RAO cranial view (5°, 35°). — **Figure 34.19** **Shallow RAO cranial view** (5°, 35°).

Photo depicts shallow RAO cranial view. — **Figure 34.20** **Shallow RAO cranial view.** Note the overlap of the distal LM, proximal LAD, proximal LCx, and proximal ramus (*circled area*). When LCx is dominant, the distal LCx and distal OMs (left PLB branches) may be well seen on cranial views, including this view, but more so on the LAO cranial view.

D. LAO cranial (40° LAO, 30° cranial)

This view allows a good assessment of the mid and distal LAD, as well as the diagonal and septal branches that originate from the mid and distal LAD. The distal LM, proximal LAD, and proximal LCx are overlapped and foreshortened. The LCx is not well seen because of its overlap with the OM branches, but the mid/distal segments of the OM branches may be well seen as they run over the heart border (Figures 34.21–34.24). Similarly to the AP cranial view, the distal LM bifurcation may be well seen without foreshortening in patients with a vertical heart or long LM, particularly with deep inspiration.

Schematic illustration of LAO cranial view (40°, 30°). — **Figure 34.21** **LAO cranial view** (40°, 30°). The LCx and OMs run on the border of the heart shadow in this view, whereas the LAD runs over the center of the heart shadow, parallel to the spine. Steeper LAO is required to move the LAD away from the spine. The diagonal and OM branches are in the sector between the LAD and LCx.

Schematic illustration of LAO cranial view. — **Figure 34.22** **LAO cranial view.** Note the overlap at the level of the distal LM.

Schematic illustration of LAO cranial view showing a dominant LCx. — **Figure 34.23** **LAO cranial view showing a dominant LCx.** The distal PLBs and PDA are well seen on this view. This view is the best view for the distal, dominant LCx.

This is also the best view to determine whether the LCx is a dominant LCx (Figure 34.23). In such a case, the LCx is seen looping all the way down the AV groove until the crux and giving a left PDA which runs parallel to the LAD. Thus, the LAO cranial view allows a good assessment of the distal, dominant LCx as well as the left PDA, the same way it allows a good assessment of the distal RCA and right PDA.

This view is also the view that best differentiates a large Dg branch from the LAD in the case of a totally occluded LAD. Two features distinguish the LAD from an enlarged diagonal:

The diagonal loops to the left and reaches toward the border of the heart shadow, whereas the LAD runs parallel to the spine and loops at the apex (Figures 34.25, 34.26). Occasionally, in an enlarged LV, the apex is moved to the left and thus the LAD course may simulate a diagonal course.
The LAD always gives septal branches, straight parallel branches which buckle very little in systole. In contrast, the diagonal and its branches buckle and curl in systole.

Shallow RAO cranial may also help define a dominant LCx, and may help in the LAD/diagonal differentiation when the LAD is totally occluded.

Schematic illustration of LAO cranial view of the patient from Figure 34.25. — **Figure 34.26** LAO cranial view of the patient from Figure 34.25. What seems like LAD on the RAO caudal view is actually a ramus or a high OM. On Figure 34.25, the outmost branch indicated by the arrow is a diagonal branch (which runs on the heart border of an RAO caudal view), while the other two branches, including the large branch that mimics LAD, are OM branches.

E. RAO cranial (30° RAO, 30° cranial)

Similarly to other cranial views, this view allows good assessment of the mid and distal LAD and the diagonal branches originating from the mid and distal LAD, (Figures 34.27, 34.28). Compared to AP cranial, there is greater superimposition of diagonal branches and wider diaphragm excursion over the coronary arteries, making this view suboptimal. AP cranial is also superior in quality to LAO cranial, which overlaps considerably with the moving diaphragm and the spine. AP cranial is often the best LAD PCI view.

Schematic illustration of RAO cranial view (30°, 30°). — **Figure 34.27** **RAO cranial view** (30°, 30°). The circled area is the area where the distal LM, proximal LAD, first diagonal, and first OM overlap.

Schematic illustration of best views for ostial left main, and best views for distal left main. — **Figure 34.28** Best views for ostial left main, and best views for distal left main.

F. Other views: 90° left lateral, LAO straight, RAO straight

The 90° left lateral view is appropriate for the assessment of the very proximal and the distal LAD. It is usually inadequate for the assessment of the mid-LAD, because of LAD–diagonal overlap at the mid-LAD level. It is particularly useful when other views do not adequately display the ostial/proximal LAD and may be the only view that shows the ostial LAD.

RAO straight resembles RAO caudal, and LAO straight resembles LAO cranial, with more overlap. Straight views are particularly useful during interventions in obese patients. They reduce the blurriness induced by soft tissue (caudal views) or the diaphragm (cranial views).

G. Views useful for left main assessment

For ostial LM: LAO and AP views, straight or cranial. Specifically, the shallow LAO straight view (10–15°) may be the best view for ostial LM and moves it away from the spine. As shown under Figure 35.1, AP and LAO are orthogonal to the left main ostium, allowing it to be well splayed. RAO views, conversely, are aligned with the left main ostium and foreshorten it. Caudal views may overlay the aortic cusp, filled with contrast, over the ostium and obscure it. Collimation with magnification over the LM is also helpful.

For distal LM: all caudal views, as well as shallow RAO straight (15°), which sees the LM as it courses anteriorly beyond its origin.

H. A minimum of two views is required for left coronary assessment

The RAO caudal view and one cranial view may be performed. The former allows the assessment of LM, LCx, and proximal and apical LAD; the latter allows the assessment of the mid and distal LAD and diagonal branches.

VII. Right coronary views

A. LAO straight

This is an en-face view of the AV groove. It allows good assessment of the proximal and mid RCA. The distal RCA, PDA, and PLBs are all overlapped (Figures 34.29, 34.30).

B. LAO cranial (30° LAO, 15° cranial)

This is the best RCA view. It shows the proximal and mid RCA, but also opens up the distal RCA bifurcation (Figures 34.29, 34.30).

Cranial views are important for the assessment of the distal RCA bifurcation, and one should obtain at least an LAO cranial or AP cranial view.

C. AP cranial (30° cranial)

This view allows the best assessment of the distal RCA bifurcation and serves as an adjunctive view when LAO cranial does not open up the bifurcation well. This view foreshortens the mid- RCA, and thus is not appropriate for mid-RCA assessment (Figure 34.31).

Tags: Practical Cardiovascular Medicine

Nov 27, 2022 | Posted by admin in CARDIOLOGY | Comments Off

Thoracic Key

Fastest Thoracic Insight Engine

Angiographic Views: Coronary Arteries and Grafts, Left Ventricle, Aorta, Coronary Anomalies, Peripheral Arteries, Carotid Arteries