grafts
An operative report describing graft number and insertions, a prior coronary angiogram or a CT coronary angiography is imperative to reduce the chances of missing a graft as well as to reduce fluoroscopy dose and procedure time spent hunting for an unknown number of grafts. An aortogram can be helpful for graft localization, potentially saving time and contrast, but it is not a panacea, because grafts can sometimes be missed completely when the take off is covered by the aorta and flow is slow. The insertions of vein grafts can vary substantially, in particular after redo bypass surgery. A rule of thumb is that the aorto‐ostial insertions of vein grafts to the left coronary system tend to arise lower and more anterior for grafts to an anterior artery (e.g. LAD) and progressively more superior and leftward as the insertion site moves more toward left lateral (e.g. diagonal, intermediate, obtuse marginal, AV circumflex). In the RAO view, left‐sided grafts can be intubated by pointing the catheter toward the right of the screen. Right‐sided grafts can be found in LAO by dragging the catheter pointing to the left of the screen along the ascending aorta starting above the RCA ostium. Selective intubation with the catheter coaxial to the graft origin is essential to optimize visualization of the distal anastomosis and grafted distal native arteries. The catheter tip is often misaligned when there is a vertical origin of a vein graft to the RCA intubated with a JR catheterA more coaxial intubation is allowed by a Multipurpose or right coronary bypass (RCB) catheter for a right‐sided graft and a Multipurpose, Amplatz or left coronary bypass (LCB) for left‐sided grafts. (Figure 4.5) The views are selected according to the native coronary segment where the graft inserts, minimizing overlapping and two perpendicular views are often required.
Figure 4.5 Guiding catheter selection for SVG to right coronary artery: (a1) JR catheter via the left radial and especially the right radial artery are rarely effective in coaxial intubation of vertical grafts for the RCA. (a2) AL1 or 2 catheters via right radial or left radial artery may require more manipulation but are more often successful (a3) Multipurpose catheters are the shape of choice via right radial, left radial artery or also femoral approach. Guiding catheter selection for SVG to circumflex artery: (b1) JR catheter or, (b2) more predictably, AL1 or AL2 catheters are effective in achieving selective engagement of the posterior lower grafts to the LCx or diagonal branches (b3) High and posterior take off can be challenging from both radial arteries and most often requires a large Amplatz guide. Guiding catheter selection for LIMA to LAD (c1) Classic IMA catheter via left radial artery (c2) classic IMA via femoral artery. Steering for selective cannulation can be made problematic by extreme subclavian tortuosities.
A recent multicenter study that included almost 1500 patients with previous CABG undergoing SVG angiography and PCI showed that the radial approach is safe and achieves similar results with overall less number of catheters and trend toward lower contrast volume as compared to the femoral approach; overall, patients undergoing procedures through the radial approach had significantly less bleeding complications. In the majority of these patients a left radial approach was preferred because of the need for concomitant visualization of the left internal mammary artery [3].
Left internal mammary artery grafts
The left internal mammary artery (LIMA) graft is usually prognostically the most important. Selective intubation of the LIMA with demonstration of the entire length of the graft and native vessel including any lesions and collateral supply is the standard. The origin of the left subclavian artery is usually engaged in the AP view. An 0.035‐inch J‐wire is used to lead before the catheter is advanced over it to reduce the risk of trauma to the vessels. If difficulty is encountered with an abnormal aortic arch, severe tortuosity, or stenosis, intubation of the left subclavian may be easier in the LAO view, using non‐selective contrast injections to delineate the anatomy and a JR rather than an internal mammary artery (IMA) catheter can help engaging the left subclavian. If it is possible to insert the catheter over a wire into the subclavian artery, an IMA catheter can be inserted via a 300‐cm J‐wire. A 0.035‐inch steerable polymer jacketed soft J‐wire (Terumo) guide is helpful if extreme tortuosity prevents passage of the standard J‐wire guide. Once the catheter tip is near the ostium of the LIMA, the AP view is most useful for engagement. The JR catheter tip is often too horizontal or too short to engage the ostium of the LIMA; in this case an IMA catheter or the even more acute shorter hook of a Bartorelli‐Cozzi (BC) catheter are the shapes of choice. Before contrast injection – including test injections – it is important to remember to check that the pressure tracing does not indicate wedging of the catheter tip against the vessel wall. If selective intubation via the femoral route proves elusive despite multiple attempts, the left radial route can offer a safer alternative A drawback of the left radial route is that right internal mammary artery (RIMA) grafts cannot be engaged, although successful intubation of the LIMA via the right radial route has been previously described [4]. A left radial approach is definitely helpful when the LIMA originates from the straight portion of the subclavian but selective cannulation may prove more difficult when it originates from the ascending limb where also catheters coming from the radial are challenged by the tortuosity of the subclavian (Figure 4.5). The first angiographic view for the LIMA requires panning from origin to the distal LAD. The views that best show the insertions are RAO cranial and left lateral. Collateral filling of other vessels should also be documented. Intubation to the diaphragm of a pedicle RIMA graft follows the same principles as for the LIMA, but with even greater care in view of the close proximity of the right internal carotid artery.
Coronary variants
Aberrant coronary anatomy is found in 0.16–1.3% of patients undergoing diagnostic angiography [5] and in 0.6% of subjects in autopsy series [6]. The anomalies can be of origination and course, of intrinsic coronary arterial anatomy (osteal stenoses, osteal aneurysm, myocardial bridging) or of termination (coronary fistula) [7]. Recent data suggest that close to 0.45% of the US population has anomalous origin of a coronary artery from the opposite sinus. [8] Some anomalies are easy to identify, such as abnormal origin of RCA (Figure 4.6) but others can be more subtle, such as anomalous non‐dominant circumflex (Figure 4.7). The culprit lesion can be missed if the aberrant anatomy is not identified (Figures 4.8 and 4.9). Systematic review to identify areas of the myocardium for which a vascular supply has not been demonstrated is helpful in this respect and also for identifying occlusions (Figure 4.9). Once it is known which vessel is anomalous, a review of the images can identify ghosting of the vessel. If there are no clues as to the origin, a systematic search starting with the most common variant is required. The diagnostic catheter shape needs to be changed as required to reach the wall of the aortic root in the area of interest. The most common coronary anomaly is an absent LMS. A slightly smaller curve catheter is required to intubate the LAD selectively (e.g. JL3.5 if JL4 preferentially and exclusively intubates the Cx). The Cx arising from the right coronary sinus can often be cannulated using the JR4 catheter, but a steep take off can require a multipurpose catheter whereas a posterior or high anterior origin can require an AR or AL shape. If the RCA arises from the left side separately from the LMS an AL1 or multipurpose catheter is most likely to be successful.