When difficulty is encountered in engaging the coronary ostia, one must first consider whether the guide catheter shape is appropriate. The use of a supportive 0.035inch guidewire within the catheter can facilitate manipulation. Similarly, deep inspiration by the patient can facilitate coronary intubation. In the case of excessive vascular tortuosity or calcification, the use of a peripheral sheath long enough to straighten the most tortuous arterial segments can improve guide catheter maneuverability. The optimal view for left and right coronary intubation is the left anterior oblique because in most patients it offers the least superimposition of the coronary ostia with the left and right aortic sinuses.
Size requirements
The advantages and disadvantages of smaller and larger catheter sizes are listed in Table 5.2. Routine angioplasty using 5 French (Fr) guiding catheters may be ideal when direct stenting is planned, but not all stents are deliverable through a 5 Fr guide and most bifurcation techniques are not applicable [1]. The general standard is a 6 Fr (2.00 mm external diameter) guide catheter which permits radial access, allows active engagement (“deep seat”), accommodates two modern rapid exchange balloons or a 1.50 or 1.75 mm rotational atherectomy burr, and uses less contrast than larger catheter diameters. For bifurcation techniques requiring the simultaneous insertion of two stents (Crush, V stenting), 7 Fr (2.33 mm diameter) guides are required. These are necessary for advanced techniques that require two over the wire (OTW) catheters and facilitate the insertion of rotational atherectomy burrs greater than 1.75 mm. For rotational atherectomy burrs greater than 2.0 mm in diameter and complex techniques requiring multiple wires, balloons, and/or stents, 8 Fr (2.66 mm diameter) guides are used. The use of guide catheters greater than 8 Fr is extremely rare in contemporary coronary intervention.
Table 5.2 The advantages and disadvantages of smaller versus larger catheter diameters have to be weighed when selecting catheter size.
| Smaller diameter | Larger diameter |
|---|---|
| Advantages | |
| Smaller puncture | Increased torque |
| Small vessel access | Increased support |
| Less traumatic radial access | Improved visualization |
| Allows deeper engagement without significant damping | Allows two balloon/stent strategy |
| Disadvantages | |
| Less torque | Larger puncture: increased access site trauma /recovery time |
| Reduced visualization | Pressure damping |
| Less support | Increased contrast use |
| Difficult or impossible to use two balloon/stent strategy |
Shape selection
Selection of guide catheter shape is critical to allow positioning of the catheter coaxially with the proximal segment of the artery, to reduce the risk of catheter‐induced vessel trauma, and optimize support during intervention. When selecting the shape of the catheter, the following factors should be considered: the curve and fit of the diagnostic catheter; size of the aortic root; origin and take off of the artery; location and complexity of the lesion; and the devices likely to be utilized during intervention.
Shape selection for the left coronary system
For the left coronary artery, catheters with a smaller curve will point upward and selectively engage to left anterior descending (LAD) and a larger curve will selectively engage and provide better support for the circumflex. The tip of Amplatz Left (AL) guides tend to point downward and are useful to selectively engage the circumflex in situations where there is a short or absent left main.
The shape of the guide catheter is an important component of the backup or support system that allows delivery of devices to the target lesion. Changing the guide catheter to improve support in the middle of a procedure can be problematic, and therefore careful consideration of guide support prior to intervention is critical. It is also important to appreciate that selection of a guide with optimal backup may obviate the need for stiffer wires or balloons, with a corresponding reduction in cost and procedure time. Although Judkins Left (JL) curves are commonly used for diagnostic intervention, these guide shapes provide less support than “backup” guides which provide contralateral aortic wall support such as the XB, EBU‐, or Q‐type curves. Because of the secondary curve on the JL, the tip may jump out of the coronary ostium when resistance is encountered. XB/EBU/Q/ Voda or similar curves provide comparatively more support with minimally increased risk of damage to the coronary ostia. AL curves are required in certain situations, but should only be used by experienced operators in view of the increased risk of iatrogenic dissection. Techniques to obtain support other than the passive support allowed by the guide catheter shape are discussed later in this chapter.
Shapes for commonly used guide catheters for the left coronary system are shown in Figure 5.1. The curve sizes of different shapes have been largely standardized and the comparable curve sizes used most commonly are shown in Table 5.3.
Figure 5.1 Shapes of a selection of guide catheters for the left coronary system.
Table 5.3 Comparability of curve sizes for different shapes of left sided guide catheters.
| AL (Amplatz) Curve | CLS or XB Curve | JL (Judkins Left) Curve | Q Curve | VL (Voda Left) Curve | |
|---|---|---|---|---|---|
| Normal | AL 1 or 1.5 | XB 4.0 or 3.5 | JL 4 | Q 4 | VL 4 |
| Dilated | AL 2 or 3.0 | XB 4.0 or 4.5 | JL 4.5 | Q 4.5 | VL 5 |
| Narrow | AL 0.75 | XB 3.0 or 3.5 | JL 3.5 | Q 3.5 | VL 3 |
