Interventional Cardiology. Группа авторов
Table 4.1, Table 4.2 and Figure 4.4. However, because of the wild degree of variation in human anatomy there are no views that will in all cases demonstrate clearly a lesion in a particular coronary segment. An example of a patient where the lesion was only clearly demonstrated after further adjustment of the gantry to unusual angles is shown in Figure 4.4.
Figure 4.4 Optimal angiographic views for specific segments of the left anterior descending artery are indicated with a green tick mark. Some views that may be useful but are not generally recommended are indicated with an orange tick mark and inadequate views with a red cross.
Left main stem
Lesions at the ostium or mid segment of the LMS are often best seen in the cranial anteroposterior (AP) (cranial 40°) or left (LAO, 30–50° left; 25–40° cranial) views. A straight AP view with only slight rightward angulation to project the catheter tip off the spine is sometimes advocated but may not be optimal because the ostium of the LMS can be projected over the left coronary sinus. The ostium of the LMS is also covered by the coronary sinus in a LAO caudal view (30–50° left; 25–40° caudal), the so‐called “spider view”, which is ideal to demonstrate the mid LMS and the LMS bifurcation. In this view the picture can be grainy and of poor quality particularly when angulation is steep and in obese patients; the image can be optimized by positioning the LMS in the center of the field and reducing the inhomogeneity induced by the presence of the lung by blanking the field from the 12 o’clock to the 3 o’clock position. If renal function allows it, a small test injection before acquisition is sensible because a more horizontal axis of the heart can require steeper caudal angulation and occasionally overlap at the LMS bifurcation can be separated by rotating more steeply to the left or toward AP caudal.
Left anterior descending
Separation of the bifurcation of the LMS in the LAO caudal view shows the ostium of the LAD clearly, with some foreshortening of the proximal LAD, and a good separation of the origin of the left circumflex and the first diagonal: for these reasons the LAO caudal view is useful for wiring the proximal LAD, for stent positioning at the ostium of the LAD or across the LM bifurcation. If possible, it should be avoided as a working view because X‐ray attenuation caused by the highly angled projection through the spine results in higher X‐ray doses. Alternative working views for the LAD ostium include RAO or AP caudal views. After wiring the LAD in a caudal view, operators move to a cranial view which shows more clearly the mid LAD and separates diagonal and septal branches. In the RAO cranial, more than 30° of rightward angulation is sometimes required to move the circumflex off the region of interest. Although the RAO cranial view can clearly demonstrate lesions in the proximal and mid LAD, this is not the ideal working view because steep rightward angulation over 40° is required to eliminate overlap with diagonals and wide diaphragmatic excursions during breathing cause highly variable contrast inhomogeneities in the field of view. Simply moving the gantry from AP to a steep 35‐40° AP cranial elongates the proximal LAD, reduces the superimposition with the left circumflex and separates the diagonals to the right of the screen. A rightward tilt of less than 5° may be required to separate the proximal segment from the spine and avoid superimposition with the mid catheter or sheath in the aorta, in the rare instances a femoral approach is used. The AP cranial is an excellent standard working view for the proximal and mid LAD and is less affected by movement of the diaphragm. For diagnostic purposes, the ostia of the diagonals may be better seen in the LAO cranial view. However, LAO cranial is seldom used as a working view because a deep breath hold is required to reduce foreshortening and superimposition of the diaphragm over the proximal and mid LAD, a maneuver that can disengage the catheter during radial approach. The body habitus of some patients also requires steep leftward angulation to project the LAD off the spine. The left lateral is an alternative, though less frequently used, working view for lesions in the proximal, mid and particularly for the distal LAD. If the only vessel of interest is the LAD, as the anterior chest where the LAD runs is not covered, it is not necessary to ask patients to remove their arms from the field of view by keeping them above their heads, a movement impossible in case of a radial approach and uncomfortable, especially for elderly patients with arthritis old shoulder injuries.
Modern X‐ray system have sharp definition of the vessel contours also using a relatively wide field of view (23 cm/9 inch), imaging the entire heart except in case of severe enlargement and offering off‐line electronic magnification to study vessel details. These wide fields of view reduce radiation burden, especially if appropriate filtering is used, and allow fitting all the arteries without panning. For 18 cm/7 Fr or less panning is usually required in the RAO cranial and LAO cranial views to image the distal LAD. Smooth slow panning allows the X‐ray generator to adjust automatically to changes in X‐ray attenuation. The lateral view is a good alternative for demonstrating the distal LAD around the apex but can also require controlled movement of the table during the acquisition toward the floor and/or in the direction of the head. The RAO caudal view can include the distal LAD without the requirement for table movement or being affected by diaphragmatic movement.
Circumflex
The circumflex ostium can be clearly seen together with the LMS bifurcation in the LAO caudal view. Occasionally, eccentric ostial lesions not clearly seen in other views can be delineated in the RAO cranial view although steep angulation may be required. The RAO caudal is the most useful diagnostic view for the circumflex and can clearly define lesions in the ostium, proximal, and mid vessel as well as the bifurcations and obtuse marginals. To obtain a working view with improved image quality by eliminating overlap with the diaphragm and reduced X‐ray attenuation, the view can be modified to AP caudal with only 10–15° rightward angulation. RAO or LAO with cranial angulation can be required to view lesions in the distal circumflex when the RAO caudal is suboptimal. If the circumflex is dominant, the LAO cranial or AP cranial views may open up the distal bifurcation and elongate the posterior descending artery. Optimal angiographic views for specific segments in the circumflex are shown in Figure 4.8a.
Right coronary artery
Views that reliably demonstrate the full length of each coronary segment while minimizing foreshortening and overlap for the RCA are shown in Figure 4.7b. Usually, the only two views required to demonstrate lesions in the proximal, mid, and distal RCA are LAO and RAO, because of the absence of side branches in these segments. Ostial lesions in the RCA are often detected in LAO but can be significantly foreshortened in this view. If stent placement is being considered, finding the least foreshortened segment can facilitate accurate positioning at ostium. The ostial segment and proximal RCA often lay perpendicular to the X‐ray beam in the AP cranial and LAO caudal views, despite variation in the origin of the RCA toward anterior or posterior. The lateral view with cranial angulation can identify occasional highly eccentric ostial lesions not clearly seen in other views. The lateral view can also help to better delineate lesions in the mid RCA or when right ventricular branches overlap the main vessel.
The distal RCA, PDA, and posterior left ventricular (PLV) branches lie posterior to the heart and require cranial angulation (in LAO) or caudal angulation (in RAO or AP) to be visualized without overlap. Many operators routinely include a third view, either AP cranial or LAO cranial, in addition to LAO and RAO as standard during diagnostic imaging.
Vein