The use of the left internal mammary artery (LIMA) has been standard practice for the last 10–15 years, so that most patients after bypass surgery require the evaluation of these grafts, by far the most important in terms of prognosis. The origin of the subclavian artery can be most easily engaged in a left anterior oblique view (40–60°) and the use of a gentle 5 French diagnostic catheter is unlikely to damage even a calcified aorta or ostia of the cranial vessels. Occasionally, a non-selective injection at the ostium of the left subclavian or innominate artery can be useful when important tortuosity or narrowing of these vessels are expected. Once the right coronary artery or LIMA catheter are positioned at the ostium of the left subclavian artery, it is worthwhile rotating the x ray gantry to an AP or a slightly right anterior oblique angulation to define the origin of the internal mammary from the subclavian artery. In older patients with calcification and tortuosity, a 0.035 inch J tipped guide wire should be used to lead the diagnostic catheter in order to minimise trauma. It is not sufficient merely to confirm patency. The injection should offer complete visualisation because the presence of distal stenoses (anastomotic or in the distal native vessels) needs to be excluded and collaterals for other occluded vessels must be visualised.
The selective visualisation of the mammary artery is more easily achieved with a specially designed LIMA catheter which has a longer tip than the classical right Judkins catheter. However, the presence of severe tortuosity of the proximal subclavian can make manipulation of the LIMA catheter very difficult. Occasionally, other types of LIMA catheter with a “hook like” shape (Bartorelli, etc) can be helpful, especially if the LIMA catheter tends to have an excessive horizontal orientation when withdrawn around the curve of the subclavian artery. The alternative approach of injection through slightly larger catheters (6 French large lumen diagnostic) or with the use of power injectors, possibly combined with occlusion of the brachial artery with a pressure cuff, can occasionally avoid the risks of a true superselective injection of the LIMA in very tortuous and frail subclavian vessels. Please note the importance of checking carefully for a normal pressure trace to exclude wedging of the catheter against the vessel wall before any injection, including test injections.
In the most complex cases steerable wires (Whooley) can be used to engage the ostium of the LIMA, with the catheter subsequently advanced over the wire. This manoeuvre, however, has an inherent risk of ostial damage. A left radial approach is occasionally the only and often the safest solution if multiple attempts from the groin remain unsuccessful. The problems become more difficult to overcome for the right internal mammary artery because of the more tortuous course from the ascending aorta. Since in most cases a LIMA will also be present, the right radial approach unfortunately cannot be used for visualisation of both mammaries, although some operators report high success with techniques for visualisation of the LIMA from the right radial approach.7
In the case of the right internal mammary, the same principles of cannulation of the left subclavian artery are applied with greater care to avoid trauma to the right common carotid artery.
Regarding coronary views, for both grafts and mammary arteries the optimal projections are similar to the projections recommended for the native arteries to which the grafts are anastomosed. We will therefore require an AP cranial view or right cranial view for the mid LAD, a right caudal view to visualise the distal LAD, a lateral view or a spider view for better visualisation of the distal anastomosis and to exclude adhesion of the left internal mammary to the sternum. For anastomosis to posterolateral or diagonal branches, right cranial views offer an optimal elongation of the vessel and visualisation of the distal branches. For right coronary artery grafts often anastomosed to the PDA or posterolateral branches of the right coronary artery, or both, it is necessary to open the distal right coronary artery bifurcation using AP cranial or left cranial views.
The right gastroepiploic artery (GEA) has been used as a conduit for bypass surgery, usually when mammary and saphenous vein grafts are unavailable. Angiography of this vessel is performed by first entering the common hepatic artery using a cobra catheter. The operator then advances a torquable hydrophilic guidewire to the gastroduodenal artery and then to the right GEA. Exchanging the cobra catheter for a multipurpose or right Judkins will permit selective angiography of the right GEA.