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

AP, anteroposterior; LAD, left anterior descending; LAO, left anterior oblique; PDA, posterior descending artery (from RCA); RAO, right anterior oblique; RCA, right coronary artery.

^* Horizontal hearts.

From Kern MJ, ed. The cardiac catheterization handbook, 2nd ed. St Louis, MO: Mosby, 1995: 286.

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

Modified from Sheehan F, Braunwald E, Canner P, et al. The effect of intravenous thrombolytic therapy on left ventricular function: a report on tissue-type plasminogen activator and streptokinase from the Thrombolysis in Myocardial Infarction (TIMI) Phase I Trial. Circulation 1987;72:817–829.

Angiographic Classification of Collateral Flow

Collateral flow can be seen and classified angiographically. The late opacification of a totally or subtotally (99%) occluded vessel through antegrade or retrograde channels will assist in correct guidewire placement, lesion localization, and a successful procedure. The collateral circulation is graded angiographically as follows:

Collateral visualization will help establish the size of the recipient vessel for the purposes of selecting an appropriately sized balloon. Determining whether the collateral circulation is ipsilateral (e.g., proximal RCA to distal RCA collateral supply) or contralateral (e.g., circumflex to distal RCA collateral supply) and exactly which region will be affected should collateral supply be disrupted is important in order to be able to gauge procedural risk. The evaluation of collaterals must be included when making decisions on which vessels should be protected or lost during coronary angioplasty.

Assessment of Coronary Stenoses

The degree of an angiographic narrowing (stenosis) is reported as the estimated percentage lumen reduction of the most severely narrowed segment compared to the adjacent angiographically normal vessel segment, seen in the worst x-ray projection. Because the operator uses visual estimations, an exact evaluation is impossible. There is a ± 20% variation between readings of two or more experienced angiographers. Stenosis severity alone should not always be assumed to be associated with abnormal physiology (flow) and ischemia. Moreover, CAD is a diffuse process, and thus minimal luminal irregularities on angiography may represent significant albeit non-obstructive CAD at the time of angiography. The stenotic segment lumen is compared with a nearby lumen that does not appear to be obstructed but that may have diffuse atherosclerotic disease. This explains why postmortem examinations and IVUS imaging describe much more plaque than is seen on angiography. The percent diameter is estimated from the angiographically normal adjacent segment. Because coronary arteries normally taper as they travel to the apex, proximal segments are always larger than distal segments, often explaining the large disparity between several observers’ estimates of stenosis severity. Area stenosis is always greater than diameter stenosis and assumes the lumen is circular, whereas the lumen is usually eccentric. In general, four categories of lesion severity can be assigned:

Technical note: Stenosis anatomy should not be confused with abnormal physiology (flow) and ischemia, especially for lesions 40% to 70% narrowed. For nonquantitative reports, the length of a stenosis is simply mentioned (e.g., LAD proximal segment stenosis diameter 25%, long or short). Other features of the coronary lesion may not be appreciated by angiography and require IVUS imaging. Anatomic factors producing resistance to coronary flow include factors producing resistance to flow across a coronary stenosis, such as entrance angle, length of disease, length of stenosis, minimal lumen diameter, minimal lumen area, eccentricity of lumen, area of reference vessel segment, and viscosity (Fig. 3-3B).

Fluoroscopy Times

A study by Pattee et al. (1993) of radiation risk to patients from coronary angioplasty indicated that radiation doses varied considerably during the procedure because of large differences in exposure times. Skin exposures estimated for PCI are, on average, higher than for other x-ray procedures and the cancer mortality risk does not exceed the mortality risk of bypass surgery (Table 3-5). Good professional practice requires maximal benefit-to-risk ratio for angioplasty procedures employing high-dose fluoroscopy or cineradiography. Device specific procedure times may be longer than routine stent placement (Table 3-6).

^{Table 3-5} Organ Doses and Risks of Cancer Mortality for an Average Coronary Angioplasty Procedure

^* 1 Gy = 1 J/kg = 1 rad.

From Pattee PL, Johns PC, Chambers RJ. Radiation risk to patients from percutaneous transluminal coronary angioplasty. J Am Coll Cardiol 1993;22:1044–1051.

^{Table 3-6} Estimated Radiation Entrance Exposure of Patients Using Phantom Model Data

R, RAD.

From Federman J, Bell MR, Wondrow MA, et al. Does the use of new intracoronary interventional devices prolong radiation exposure in the cardiac catheterization laboratory? J Am Coll Cardiol 1994;23:347–357.

Angulated views increase radiation exposure. Left anterior oblique views produce 2.6 to 6.1 times the dose of radiation for the operator of equivalently angled RAO views (Table 3-7). Steeper LAO views also increased operator dose. LAO 90 degrees produces 8 times the dose of LAO 60 degrees and 3 times the dose of LAO 30 degrees. Fluoroscopy produced more radiation than cine during angioplasty, by a factor of 6:1. Reducing the steepness of angulation reduces operator radiation dosage.

^{Table 3-7} Radiation Dose and Angulation

LAO, left anterior oblique; RAO, right anterior oblique.

Renal Arteriography

Selective renal arteriography or arteriography obtained from aortic flush is used to evaluate the renal artery origins and vasculature. Remember, for renal artery identification during aortography, the origins of the arteries usually arise at the L1 vertebra (just below the T12 ribs). Selective renal arterial injections provide the most detail. The LAO projection often provides the best view of the renal artery ostia in a majority of patients. Acute angled takeoffs of the renal artery may require specially shaped catheters or a brachial arterial approach from above. Atherosclerotic disease of the renal artery usually involves the proximal one-third of the renal artery and is seldom present without abdominal atherosclerotic plaques. A renal artery stenosis artery is rarely the sole determinant for surgery or angioplasty. Refractory hypertension and determination of the renin-angiotensin levels are usually the indicators for an interventional (angioplasty or stent) procedure. Renal artery fibromuscular dysplasia may occur and appear as atherosclerotic disease. This finding is often present in middle-aged women in whom other vessels are involved, most commonly cerebral or visceral arteries. In contrast to atherosclerotic narrowing, the proximal one-third of the main renal artery is usually free of disease.

Aortography of the thoracic and abdominal aorta is used to assess disease, dissections, and course of the vessel to perform and plan interventions. In high-risk PCI, abdominal aortographic is useful prior to insertion of IABP or LV support devices.

Lower Extremity Angiography

Angiography of the lower extremities is part of peripheral vascular interventions, discussed in Chapter 11. Based on clinical signs and symptoms of arterial insufficiency to the legs, suspected obstructions of the vessel are initially screened with noninvasive studies (i.e., ankle brachial index). Angiography is performed with small-diameter (5 F) catheters and reduced contrast volumes (10–20 mL over 1–2 sec) which are injected, panning down and following the artery course to the most distal locations. Angulated views may be necessary to open bifurcations and overlying vessels that obscure the vessel origin. Panning down to the ankle must be tested before obtaining final views. Digital subtraction techniques are commonly available in modern laboratories. Nonionic contrast agents are less painful than ionic media for peripheral angiography.

One major challenge encountered with femoral-iliac angiography is the contralateral (opposite leg) approach, crossing over the aortic bifurcation of the iliac vessels, especially in patients with high bifurcation or prior aorto-bifurcation graft. To enter the opposite iliac artery, a right Judkins or internal mammary artery graft catheter or other special catheters (crossover, Simmons catheter, etc.) is advanced with a guidewire over the bifurcation and down into the opposite femoral artery. The wire is passed into the selected artery. The catheter may be advanced and exchanged (over a long 300-cm wire) for an appropriate angiographic or balloon dilatation catheter, as required.

The area most frequently involved in peripheral atherosclerotic disease is the distal superficial femoral artery at the abductor canal (Fig. 3-7). The calf (tibial), and knee (popliteal) arteries are the next most commonly involved vessels after the superficial femoral artery. Disease in the deep femoral artery (femoral profunda) is rare. Pathways of collateralization are often rich and varied in patients with chronic distal femoral artery disease, especially in total occlusion of the superficial femoral artery that reconstitutes at or below the knee, close to the branching trifurcation of the tibial and deep peroneal arteries. Determining the level of reconstitution of collateralized vessels and distal runoff is crucial in determining the feasibility of revascularization. Magnified images focusing on the area of interest are frequently needed.

Diagrams and nomenclature for additional angiographic studies are shown in Figures 3-8 through 3-12; see also Chapter 11.

Figure 3-8 Pelvic and proximal femoral arterial branches.

(From Johnsrude IS, Jackson DC, Dunnick NR. A practical approach to angiography, 2nd ed. Boston: Little, Brown, 1987.)

Figure 3-9 Lower extremity vascular anatomy.

(From Medical Learning Incorporated, with permission.)

Figure 3-10 Ascending aorta and head and neck vessels.

(From Medical Learning Incorporated, with permission.)

Figure 3-11 Commonly accessed arteries of the abdomen.

(From Medical Learning Incorporated, with permission.)

Figure 3-12 Vascular anatomy of the upper extremity.

(From Medical Learning Incorporated, with permission.)

Indications

Atropine may be used to prevent bradycardia but a pacemaker should be on standby for patients who experience severe bradycardia during coronary injections.

Temporary transvenous pacemaker placement can be achieved through the internal jugular, subclavian, brachial, or femoral vein route. The easiest access is usually the vein next to the arterial entry site. Right ventricular pacing is best accomplished with a 5 F balloon-tipped pacing catheter because there is a reduced incidence of perforation of the thin free wall or apex of the right ventricle when the balloon is inflated.

Cutaneous patch pacemakers are also effective until secured pacing routes can be established. Muscle contractions induced by the cutaneous pacing patches are uncomfortable so the patient should be well sedated.