Interventional Cardiology. Группа авторов

      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 (Terumo) is connected to the guide catheter of 6 or 7 Fr. The conventional Y‐connector is attached to Kiwami® (child) which was inserted in the 6 or 7 Fr (mother) catheter. Because the effective length of Kiwami® is 120 cm, the projected length from the mother catheter differs depending on the length of mother catheter used [12]. The 4 Fr‐in‐6 Fr Kiwami® catheter is probably the most deliverable among the GC extensions, but has the smallest lumen (0.050 inch) and requires meticulous attention to details to avoid air embolism [13].

      Guide catheter extensions

      In the GuideLiner® catheter (Teleflex‐Vascular Solutions, Maple Grove, MN, USA) a coaxial short distal soft catheter is mounted at the tip of a long stainless‐steel rod, which extends outside the guide catheter. This enables deep intubation of the coronary artery to achieve extra support and improve coaxial alignment. It has a coaxial 20 cm long catheter with a radiopaque marker situated 2.7 mm from the tip from the tip, joined to a 125 cm compact metal hypotube by means of a ring (“collar”, made of metal in the first version and replaced by a lubricious polymer in the V2 version), which can be deployed through the existing Y‐adapter for rapid exchange delivery. The device is available in three sizes: 5‐in‐6 (0.056 inch internal diameter (ID)), 6‐in‐7 (0.062 inch ID), and 7‐in‐8 (0.071 inch ID). Its monorail design permits rapid exchange and offers important advantages over its predecessors, the “five‐in‐six mother and child” catheters Heartrail II®, which had a coaxial system that made their utilization more demanding [11]. Furthermore, rapid exchange helps with deployment through the existing hemostatic valve without extending the guiding catheter length, and so does not limit the useable length of balloons and wires. Other Companies designed similar catheters such as the Guidezilla™ (Boston Scientific, Marlbourough, MA, USA), Telescope (Medtronic, Minneapolis, MN, USA), Gideon (IVS, Maastricht, The Netherlands), claiming more lubricious coatings or smoother connections between hypotube and distal catheter. The Guidezilla is probably the most widely used guide extension after the GuideLiner, is mounted on a monorail system, which extends the guide catheter and enables deep intubation of the coronary artery. It is made of a distal end of 25 cm covered by a hydrophilic polymer, joined to a 120‐cm compact metal hypotube. The distal flexible extension consists of a pair of radiopaque markers, the first situated 2 mm from the tip and the second 3 mm from the transition collar. The device is available in one size 5‐in‐6 and compatible with guide catheter ≥6 Fr. An additional system, with sizes compatible also with 5 Fr guiding catheters, is the Guidion rapid exchange guide extension catheter (IMVS, Roden, the Netherlands).

      De Man et al. [14], published results from the Twente GuideLiner Registry identifying three primary indications for the use of the device: improvement of back‐up and facilitated stent delivery (59%), more selective contrast injection (13%), and improvement of alignment of the guide (29%). Moreover, they found a device and procedural success rate of 93% and 91%, respectively, without major complications and a small incidence of minor complications (3%). The safety and efficacy of utilizing the GuideLiner monorail catheter to treat complex lesions was confirmed in recent experience published by Chan et al and Fabris et al. [15,16], showing good performance of the device in the settings of bypass graft intervention, bifurcation lesions, and chronic total occlusions. In order to avoid damage of the proximal vessel, especially in case of non‐coaxial alignment of the coronary ostium and extreme proximal vessel tortuosity (e.g. a shepherd’s crook’s origin of the RCA”), a balloon advanced distally can be used to reduce the chance of damaging the ostium and the proximal vessel by acting as centering rail). If the guide extension does not advance this can be caused by vessel tortuosity and poor GC back‐up and solved inflating the distal balloon to gently attract it or can be caused by presence of proximal stenoses or calcifications, in need of effective predilatation.

Guidewire selection

      Guidewires are required to cross the target lesion and to provide support for the delivery of balloons, stents, and other devices while at the same time minimizing the risk of vessel trauma. A guidewire needs to be steerable, visible, flexible, lubricious, and supportive. There is no single wire that has the perfect combination of all these characteristics. Variations in guidewire components have produced a wide range of wires suitable for different anatomies and lesion characteristics. Wire selection depends on which features are thought to optimally facilitate angioplasty for a given clinical and angiographic scenario.

      Guidewires typically