[6] (Figure 5.5).
Figure 5.5 Approaches to increase guide catheter support for treating complex lesions. Guidewires.
Active support
Guide catheters smaller than 6 Fr can be advanced over the guidewire and balloon catheter shaft to sub‐selectively engage the proximal or mid segment of an artery (Figure 5.5). This technique is also referred to as active engagement or “deep seating” of the guide catheter. The risk of damage to the artery can be minimized by ensuring that the catheter is advanced coaxially over a balloon already inside the vessel. Stabilization of the system while advancing the guide catheter is sometimes required and can be achieved by inflating a balloon within the artery. When considering the use of active support, it is important to bear in mind that deep engagement of large arteries can cause profound ischemia. The use of side holes may not prevent and may even delay detection of catheter‐induced ischemia. A further risk is that of air embolism following aspiration through the Y‐connector while the back pressure in the guide catheter is reduced as a result of damping inside the artery. Despite these risks, for a skilled operator capable of rapidly advancing and withdrawing catheters, active support offers an efficient solution in most cases.
Hybrid support
Several additional strategies have been described based upon the concept of inserting an additional device, wire, balloon, or other catheter specifically to augment support when active and/or passive support of the guide catheter proves insufficient (Figure 5.6).
Figure 5.6 “Intraluminal” hybrid support techniques that can be used to substantially augment guide catheter support when treating complex lesions.
Wire support
The buddy wire technique refers to the passage of a second or third guidewire distal to a target lesion to provide additional support for delivery of angioplasty equipment. This is a commonly used strategy for crossing difficult lesions with a balloon or a stent [7]. The additional wire provides a rail that facilitates advancement across calcification, tortuosity, or recently deployed stents. The wire facilitates active engagement of the guide catheter and can straighten tortuosity when a supportive wire is used. This technique is also the first essential step for the distal anchor balloon technique. Although it can at first appear to be counterintuitive, advancing an additional wire into a branch that lies proximal to the target lesion, this may increase support enough to allow passage of a balloon, stent, or additional wire along the first wire into the tortuous distal vessel (Figure 5.6) and is anyway the first step for a side branch anchoring technique [8]. Using a buddy wire is a simple strategy that can be facilitated using a dual lumen microcatheter in case of excessive tortuosity or presence of dissections post initial balloon dilatation. This avoids the risks of deep engagement or the delays and potential difficulties of upgrading the guide catheter. A floppy, steerable wire can advance easily and be exchanged using an OTW catheter for a wire with a more supportive shaft but soft flexible tip. The use of stiff hydrophilic wires as a “buddy wire” is discouraged because of the risk of perforation. Occasionally, if support from the guide and an additional wire still proves insufficient, additional techniques are needed and are delineated subsequently.
Anchor balloon technique
Inflation of an adequately sized balloon at low pressure (3–6 atmospheres) in a proximal branch can augment support by anchoring the guide catheter to the vessel and the branch (Figure 5.6) [9]. Low inflation pressures are essential to reduce the risk of dissection or damage to a small right ventricular branch or diagonal/marginal branch. In these branches, ischemia resulting from prolonged inflation is well tolerated. The technique is mostly used in treating CTO and is facilitated by a large guide catheter.
Another strategy that can be tried when a buddy wire does not resolve problems in tracking a stent to a target lesion because of tortuosity or calcification of the proximal segment, is to advance over the buddy wire a balloon optimally sized to match the diameter of the distal vessel (Figure 5.6). The balloon is positioned distal to the lesion and inflated at low pressure allowing enough space for the stent to be fully advanced across the target stenosis. It is imperative to remember that the distal anchoring balloon must be deflated and removed before the stent is deployed. In addition to providing extra support, the shaft of the distal balloon also acts as a rail to facilitate stent advancement. The operator needs to be experienced enough to anticipate when the force required may detach the stent from the balloon. Additional strategies can then be considered such as the need for better lesion preparation or the insertion of a subselectively engaged guiding catheter around the most tortuous segment, using the guide already in place or a 5 Fr in 6 or 7 Fr strategy as outlined in the next section (Figure 5.7).
Figure 5.7 Components of guidewire design.
Adjunctive techniques
Double coaxial guiding catheter technique (also known as mother–child)
By placing one guide catheter inside another, the advantages of the passive support provided by a large guide catheter are combined with the ability to actively engage the smaller catheter into the target vessel (Figure 5.5) [10]. Compatibility of different guide catheter lengths and diameter is a limiting factor. Mainly a 6 Fr, 110 cm long “child” guide catheter is combined within an 85 or 90 cm 7 or 8 Fr “mother” guide catheter. These limitations have been overcome by the use of dedicated longer and smaller coaxial catheters. The Heartrail II® “five‐in‐six catheter system” comprises a flexible‐tipped, long (120 cm) 5 Fr catheter advanced through a standard 6 Fr guiding catheter to deeply intubate the target vessel. This system uses the target vessel itself to provide the extra backup support required for stent delivery. Furthermore, the absence of a primary curve and the flexibility of its tip permit the “child” catheter to remain coaxial with the target vessel, thereby minimizing the risk of catheter‐induced coronary dissection. Use of this system has been shown to be useful in the treatment of CTO cases where such increased backup support is important. However, its use requires removal of the Y‐connector, making the procedure more demanding [11].
The Kiwami® 4 Fr‐in‐6 Fr catheter measures 120 cm, 1.43mm (outer diameter) 1.27mm (inner diameter); the inner layer is coated with polytetrafluoroethylene (PTFE) and the surface is coated with a hydrophilic surface up to 15 cm from the tip of the catheter. The backstream prevention valve
