Position for Anteroposterior Imaging

The image intensifier is directly over the patient, with the beam perpendicular to the patient lying flat on the x-ray table (Figs. 3-1, 3-2). The anteroposterior (AP) view or shallow right anterior oblique (RAO) displays the left main coronary artery in its entire perpendicular length. In this view, the branches of the left anterior descending (LAD) and left circumflex coronary arteries branches overlap. Slight RAO or left anterior oblique (LAO) angulation may be necessary to clear the density of the vertebrae and the catheter shaft in the thoracic descending aorta. In patients with acute coronary syndromes, this view will exclude left main stenosis, which can preclude or complicate PCI. The AP cranial view is excellent for visualizing the LAD with septals moving to the left (on screen) and diagonals to the right, helping wire placement.

Figure 3-1 Nomenclature for angiographic views.

(Modified from Paulin S. Terminology for radiographic projections in cardiac angiography. Cathet Cardiovasc Diagn 1981;7:341.)

Figure 3-2 Nomenclature for angiographic views. CR, cranial; CA, caudal; A, anterior; R, right; AO, anterior oblique.

(Modified from Paulin S. Terminology for radiographic projections in cardiac angiography. Cathet Cardiovasc Diagn 1981;7:341.)

Position for Right Anterior Oblique Imaging

The image intensifier is to the right side of the patient. The RAO caudal view shows the left main coronary artery bifurcation with the origin and course of the circumflex/obtuse marginals, intermediate branch, and proximal left anterior descending segment well seen. The RAO caudal view is one of the best two views for visualization of the circumflex artery. The LAD beyond the proximal segment is often obscured by overlapped diagonals.

The RAO or AP cranial view is used to open the diagonals along the mid and distal LAD. Diagonal branch bifurcations are well visualized. The diagonal branches are projected upward. The proximal LAD and circumflex usually are overlapped. Marginals may overlap, and the circumflex is foreshortened.

For the right coronary artery (RCA), the RAO view shows the mid RCA and the length of the posterior descending artery and posterolateral branches. Septals supplying an occluded LAD via collaterals may be clearly identified. The posterolateral branches overlap and may need the addition of the cranial view.

Position for Left Anterior Oblique Imaging

In the LAO position, the image intensifier is to the left side of the patient. The LAO/cranial view also shows the left main coronary artery (slightly foreshortened), LAD, and diagonal branches. Septal and diagonal branches are separated clearly. The circumflex and marginals are foreshortened and overlapped. Deep inspiration will move the density of the diaphragm out of the field. The LAO angle should be set so that the course of the LAD is parallel to the spine and stays in the “lucent wedge” bordered by the spine and the curve of the diaphragm. Cranial angulation tilts the left main coronary artery down and permits view of the LAD/circumflex bifurcation (Fig. 3-3). Too steep an LAO/cranial angulation or shallow inspiration produces considerable overlapping with the diaphragm and liver, degrading the image.

Figure 3-3 A, Diagrammatic view of left coronary artery demonstrating special positioning to best observe branch segments. (From Boucher RA, Myler RK, Clark DA, et al. Coronary angiography and angioplasty. Cathet Cardiovasc Diagn 1988;14:269–285.) B, Diagram of factors producing resistance to flow across a coronary stenosis. (1) Entrance angle, (2) Length of disease, (3) Length of stenosis, (4) Minimal lumen diameter, (5) Minimal lumen area, (6) Eccentricity of lumen, (7) Area of reference vessel segment.

For the RCA, the LAO/cranial view shows the origin of the artery, its entire length, and the posterior descending artery bifurcation (crux). Cranial angulation tilts the posterior descending artery down to show vessel contour and reduces foreshortening. Deep inspiration clears the diaphragm. The posterior descending artery and posterolateral branches are foreshortened.

The LAO/caudal view (“spider” view; Fig. 3-3) shows a foreshortened left main coronary artery and the bifurcation of the circumflex and LAD. Proximal and mid portions of the circumflex and the origins of obtuse marginal branches are usually seen excellently. Poor image quality may be due to overlapping of diaphragm and spine. The LAD is considerably foreshortened in this view.

A left lateral view shows the mid and distal LAD best. The LAD and circumflex are well separated. Diagonals usually overlap. The course of the (ramus) intermediate branch is well visualized. This view is best to see coronary artery bypass graft (CABG) conduit anastomosis to the LAD. For the RCA, the lateral view also shows the origin (especially in those with more anteriorly oriented orifices) and the mid RCA well. The posterior descending artery and posterolateral branches are foreshortened.

Angulations for Saphenous Bypass Grafts

Coronary artery saphenous vein grafts are visualized in at least two views (LAO and RAO). It is important to show the aortic anastomosis, the body of the graft, and the distal anastomosis. The distal runoff and continued flow or collateral channels are also critical. The graft vessel anastomosis is best seen in the view that depicts the native vessel best. A general strategy for graft angiography is to perform the standard views while assessing the vessel key views for specific coronary artery segments (Table 3-1) to determine the need for contingency views or an alteration/addition of special views. Therefore, the graft views can be summarized as follows:

^{Table 3-1} Recommended “Key” Angiographic Views for Specific Coronary Artery Segments

^* Horizontal hearts.

Imaging During Respiration

During diagnostic angiography, deep inspiration moves the diaphragm away from the heart to see the vessels without density overlap. However, when working with PCI equipment, deep inspiration may change the proximal course of the artery and the spatial relation of the lesion to anatomic landmarks. Knowing where the lesion is relative to these landmarks is important. Guiding angiograms should be taken in such a way that frequent inspiratory effort leading to patient fatigue during manipulation is not necessary. Select a view requiring minimal inspiratory breath holding while providing an optimum presentation of the lesion.

Power Injection Versus Hand Injection for Coronary Arteriography

Power injection of the coronary arteries has been used in thousands of cases in many laboratories and is equal in safety to hand injection. A power injector at a fixed setting may require several injections to find the optimal contrast delivery flow rate. Power injectors now incorporate hand controls, permitting precise operator touch-sensitive variable volume injection (Acist, Bracco Diagnostics) as well as a computer touch screen for precise contrast delivery settings. Typical settings for power injections are the following:

Angiographic TIMI Classification of Blood Flow

Thrombolysis in myocardial infarction (TIMI) flow grading has been used to assess, in a qualitative fashion, the degree of restored perfusion achieved after thrombolysis or angioplasty in patients with acute myocardial infarction. Table 3-2 provides descriptions used to assign TIMI flow grades.

^{Table 3-2} Thrombolysis in Myocardial Infarction (TIMI) Flow: Grade and Blush Scores

TIMI Frame Count

Contrast runoff is now performed quantitatively by using cine frame counts from the first frame of the filled catheter tip to the frame where contrast is seen filling a predetermined distal arterial end point. Myocardial blood flow has been assessed angiographically using the TIMI score for qualitative grading of coronary flow. TIMI flow grades 0 to 3 have become a standard description of coronary blood flow in clinical trials. TIMI grade 3 flows have been associated with improved clinical outcomes.

The method uses cineangiography with 6 F catheters and filming at 30 frames per second. The number of cine frames from the introduction of dye in the coronary artery to a predetermined distal landmark is counted. The TIMI frame count for each major vessel is thus standardized according to specific distal land marks. The first frame used for TIMI frame counting is that in which the dye fully opacifies the origin of the artery and in which the dye extends across the width of the artery touching both borders with antegrade motion of the dye. The last frame counted is when dye enters the first distal landmark branch. Full opacification of the distal branch segment is not required. Distal landmarks used commonly in analysis are listed here:

1. For the LAD, the distal bifurcation of the LAD artery

2. For the circumflex system, the distal bifurcation of the branch segments with the longest total distance

3. For the RCA, the first branch of the posterolateral artery

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