of the force during inflation and decrease balloon slippage. Scoring balloons have similar indications to cutting balloons, but scoring balloons are more flexible, have a better profile and can achieve a full expansion with a low inflation pressure, with consequently less trauma to vessel walls and a minor risk of coronary dissections [21,22]. Several types of scoring balloons are now available for treatment of mild to moderate calcified lesions. The AngioSculpt (Spectranetics‐Philips) is a semicompliant balloon with three spiral rectangular Nitinol scoring elements, also available in a drug‐coated version (AngioSculpt X, Spectranetics‐Philips). Developed for both coronary and peripheral vascular applications, the Angiosculpt is similarly used in highly resistant lesions when conventional balloons are unable to dilate the vessel. In a feasibility trial, the AngioSculpt balloon was used for the treatment of de novo lesions prior to BMS implantation and showed very high procedural success and a target lesion revascularization rate of 10% at 6 months [23]. These results were confirmed in an observational study, in which 37 patients treated with AngioSculpt before stent implantation were compared to 145 patients treated with direct stenting and 117 patients with traditional plain old balloon angioplasty before stent implantation. IVUS assessment showed greater stent expansion in the AngioSculpt group than in the other two groups (89% versus 74% of vessels with an area >5.0 mm2, respectively) [24].
Another focal force balloon is the Chocolate balloon (TriReme Medical, Pleasanton, CA, USA), which is a traditional semi‐compliant balloon within a nitinol cage. When the balloon is inflated, the cage restrains the balloon expansion, and the balloon protrudes from between the struts of the nitinol cage applying focal pressure to discrete areas of the plaque. Theoretically, this will result in more controlled plaque fracture. The NSE Alpha scoring balloon (B Braun, Berlin, Germany) has three triangular flexible nylon elements on the balloon surface attached only at the proximal and distal edges of the balloon. Promising results for predilatation of severe calcified lesions were shown with the leopard‐crawl technique [25]. The Scoreflex (Orbus Neich) is a semicompliant balloon with two fixed Nitinol wires on opposite sides of the balloon surface [26]. Otsuka et al. reported a case series where prolonged inflation of the Scoreflex balloon allowed adequate dilation of severe calcified plaques as shown by the ‘creep phenomenon’, whereby prolonged inflation of the balloon produces a distortion force capable of expanding a resistant calcified lesion [27]. Scoring balloons have been considered by cardiologists as an alternative to cutting balloons and, in recent years, have been preferred because of major flexibility and deliverability, although no specific randomized control trials are reported in the literature.
Non‐compliant balloon catheters
Non‐compliant (NC) balloons, unlike semi‐compliant balloons, tolerate high inflation pressures, exhibiting a small increase in diameter. NC balloons allow more uniform balloon expansion and the application of higher forces in a focal segment of a coronary vessel, avoiding dog‐bone deformation exerting excessive pressure at the edges and potentially causing coronary dissections or perforations. When facing a mild to moderate calcific coronary lesion, repeated and prolonged inflations with NC balloons should be encouraged as the first choice, especially when the calcium arc is restricted (<90°).
Sapphire II (OrbusNeich, Hoevelaken, Netherland), a last generation NC balloon, is a well‐balanced balloon catheter that crosses lesions without boundaries. This catheter offers an ultra‐low crossing profile across a broad range of configurations, including 1.0 mm diameter balloons and 150 cm shaft working length versions. Sapphire II features a flexible, supple balloon material for slender rewrap; an XD (eXtra Durable) shaft for enhanced pushability and superb kink resistance; proprietary Hydro‐X coating for lubricious crossing; and Z‐Tip technology resulting in ‘Zero’ transition between the tip and guidewire for smooth and safe penetration of the tightest of lesions.
The OPN NC balloon (SIS Medical) is a double‐layered balloon that allows high‐pressure dilatation. This balloon catheter uses twin‐layer technology to allow super high pressures within the balloon with minimal increases in diameter. This balloon can be inflated with a nominal pressure of 10 atm and a rated burst pressure of 35 atm, but the balloon was tested up to a pressure of 45 atm and many operators report very rare balloon ruptures at pressures as high as 5573 kPa 55 atm, the maximal level allowed by the special indeflator provided with the balloon. The OPN NC balloon is available in diameters ranging from 1.5 to 4.5 mm (in 0.5 mm increments) and lengths of 10, 15, and 20 mm. The OPN NC balloon is a dedicated device for the treatment of in‐stent restenosis, heavily calcified lesions or other lesions that cannot be dilated. The OPN balloon is compatible with 0.014 inch wires and 5 Fr access, but it has a high profile (0.028 inches), although this is better than scoring and cutting balloons, and so it is difficult to recross or reuse after inflation. In a retrospective study evaluating 326 undilatable lesions in which conventional NC‐balloons failed to achieve adequate post‐dilatation luminal gain, the OPN NC balloon successfully treated >90% of undilatable lesions compared with a conventional NC balloon with a 0.9% rate of coronary rupture, resulting an effective and safe strategy for treatment of severe resistant coronary lesions [28].
Microcatheters
Microcatheters constitute over the wire support systems that contribute to the success of both antegrade and retrograde recanalization techniques. They were specifically developed to enhance lesion crossing and can substantially increase the support offered to the guidewire when they are engaged within the lesion. Microcatheters also allow reshaping or changing the guidewire without losing the distal position. They prevent prolapse of the guidewire and improve its penetration ability. Microcatheters can also straighten a tortuous artery proximal to the lesion and increase the guidewire torque. They can also be used to inject contrast dye to visualize the distal vessel. Due to their small profile, they can also cross the lesion when small balloons fail to do so. A wide range of microcatheters are currently available and they can be divided into different categories according to their characteristics:
Large diameter microcatheters, such as the Corsair (Asahi Intecc, Nagoya, Japan), Turnpike and Turnpike Spiral (Teleflex, Wayne, PA, USA). Larger microcatheters are usually used to improve guidewire support during antegrade CTO crossing.
Small diameter microcatheters, such as the Finecross (Terumo, Somerset, New Jersey), Caravel (AsahiIntecc), Turnpike LP (Teleflex), and Micro 14 (BTG, London, United Kingdom). Like the larger ones, they are used to increase guidewire support but, thanks to their smaller diameter, they are also particularly useful to negotiate tortuosity and cross severe lesions.
Angulated microcatheters, such as the Supercross (Teleflex) and Venture (Teleflex), used to access side branches. Recently, the steerable microcatheter (SwiftNINJA, Sumitomo Bakelite, Tokyo, Japan), which has a remote controlled flexible tip manipulated using a dial in the handgrip, was developed, enabling the operator to change the angle of the microcatheter tip manually, and potentially makes selective catheterisation easier [29]
Dual lumen microcatheters, such as the TwinPass and TwinPassTorque (Teleflex); Sasuke (Asahi), NHancer Rx (IMDS, The Netherlands). They consist of a rapid delivery system exchange in the distal segment associated with an OTW lumen along the catheter. Although each device has its own peculiar characteristics, all these devices share a common feature, that is the presence of two lumens, whose purpose is to allow precise and independent handling of two different guidewires. The rapid exchange distal port is at the distal end of the catheter, while the OTW lumen starts some mm more proximally and runs the whole length of the catheter. Two radiopaque markers are positioned in order to identify the exit ports of both lumens. The role of dual lumen microcatheters has been expanding [30,31] and they can be used for: parallel wire technique; antegrade wiring of CTOs with side branch at the proximal cap; wiring distal true lumen without losing access to a distal side branch near the distal cap; antegrade wiring of the distal true lumen if the externalized retrograde guidewire crossed a collateral close to the distal.
Plaque modification microcatheters, such as the Tornus (Asahi Intecc), and Turnpike
