INTRODUCTION

The major limitations of balloon angioplasty involved acute problems (failure to achieve a satisfactory dilatation of a lesion as well as acute complications, including dissection of the vessel) and short- to medium-term restenosis. Failure to achieve a reasonable dilatation occurred in very fibrotic and calcified lesions, and in other vessels related to the bulk of focal disease and elastic recoil of the vessel. Certain anatomic situations were also difficult to treat, including aorto-ostial lesions and bifurcations. With the latter, plaque shift from one arm of the bifurcation to another could only partially be overcome using kissing balloon techniques. Dissections occurred particularly in calcified lesions, eccentric bulky lesions, lesions on bends or in tortuous segments of the vessel and in patients with very diffuse disease.

Although stenting has become the default method of PCI, the understanding in the early and mid-1980s of the components of acute failure and restenosis led to two major lines of development – atherectomy and ablative methods as well as methods of scaffolding the vessel. The new technologies that emerged included the directional atherectomy device and two methods of ablation, namely laser techniques and rotablation. Although some of the scenarios when these devices were used can now be treated with stents, certain clinical and anatomic scenarios exist where the use of ablative methods are essential to allow optimal delivery and expansion of stents and in some cases they may be the only means of achieving percutaneous dilatation of a lesion. One of the worst clinical situations to occur in the current era favouring direct stenting is the delivery of a stent to a previously unrecognised undilatable lesion. Only experience, recognition of a number of clinical clues that this situation might be met, and the ability to use ablative technologies can prevent this. This chapter will review the use of atherectomy devices and coronary rotablation.

DIRECTIONAL ATHERECTOMY

This is now largely a historical review, as directional coronary atherectomy (DCA) is now used very infrequently. Many of the devices previously available are no longer manufactured but Guidant (Guidant, Santa Rosa, CA) continues to manufacture the Flexi-Cut™ device and the FoxHollow SilverHawk™ device (FoxHollow Technologies, Redwood City, CA, USA) is also available.

Directional coronary atherectomy was developed by John Simpson to enable debulking of lesions. It was argued that excision of atheromatous material would overcome many of the limitations of balloon dilatation alone, allowing for better dilatation of the lesion with less dependence on stretch (and thus barotrauma), more controlled dilatation (and thus fewer dissections), and that there would, as a result, be better acute clinical results with less restenosis. The initial registries appeared favourable, but the results of several randomised trials were disappointing. The major studies of DCA are listed in Table 14.1. In particular, the use of DCA resulted in a relatively high peri-procedural release of cardiac enzymes, and clinical results were either only marginally better or in some cases appeared worse.^13–15 There are several reasons why early registry experience is not always translated into clinical benefit in a multi-centre randomised trial. These include the performance of a trial before the technique has been adequately developed, designing a trial that partially reflects the learning curve of operators with only limited experience of the technique and, perhaps most importantly, the fact that early registry experience is obtained in carefully selected patients by operators who have the greatest experience of the technique. Moreover, the original concepts of why DCA might be favourable might have been countered by the stimulus to restenosis caused by cutting into the plaque.

TABLE 14.1 MAJOR STUDIES OF THE ROLE OF DCA

Although the CAVEAT and CCAT trials did not establish a clear benefit from DCA, possibly because of inadequate debulking and a higher complication rate compared to balloon angioplasty alone, the OARS, BOAT, ABACAS and GUIDE II studies suggested that optimal debulking, with attempts to reduce residual plaque volume to a minimum (aided if necessary by IVUS guidance), would result in lower restenosis rates. A residual angiographic percent diameter stenosis after DCA (with or without adjunctive balloon angioplasty) of <10–15% was aimed for. However, the higher CK release during procedures remains an issue and given that DCA is more technically demanding, the emergence of stenting as an easier-to-use technique with equal or better results has resulted in a major reduction in the number of DCA procedures being performed worldwide. However, when only BMS were available, the Japanese START study suggested that DCA could still be considered as an alternative to stenting as it achieved a lower rate of restenosis with no differences in clinical events.⁸

Several generations of devices were produced by Devices for Vascular Intervention (acquired initially by Guidant Ltd and subsequently by FoxHollow). Following the original AtheroCath®, sequential improvements were seen in the SCA-1™, SCA-EX™, Short-Cutter™, the GTO®, the Bantam™ and the Flexi-Cut™ devices, with improved debulking capability and use even in partially calcified lesions. The original devices needing 10F sheaths and guide catheters gave way to 8F-compatible devices. Currently, only the Flexi-Cut™ device is available (Fig. 14.1). The technique requires stiffer than average guide catheters such as the Viking XT™ range (Guidant) with stiff wires such as the Iron Man™ (Guidant).

Figure 14.1 Directional atherectomy.

The device is inserted into the vessel, rotated until the cutting window is lined up with the side of the vessel containing the bulk of the lesion, the cutter is then drawn back and the balloon on the side of the device opposite to the window is then inflated at low pressure. The balloon stabilises the device and pushes the cutting window against the plaque. The device is then activated and the rotating cup-shaped cutter is advanced, slicing off the atheroma and pushing it forward into the collection nosecone. The balloon is then deflated, the device rotated slightly and further excisions made until adequate atherectomy has been performed. Different sized catheters are available for different vessels and lesions. In smaller vessels, the development of ischaemia during the procedure sometimes requires withdrawal of the device back into the guiding catheter between cuts. This is less of a problem with the Flexi-Cut™ device.

More recently, the FoxHollow SilverHawk™ Plaque Excision System has been introduced (Fig. 14.2), which has the advantage of being 6 F compatible and it does not have a contra-lateral balloon opposite the cutting window but instead a unique hinge design.¹⁶ This potentially reduces barotrauma. Three tip lengths are available with different collection chambers, allowing for a number of clinical scenarios in coronary cases, and the device can be used in vessels ranging from 1.5 to 3.5 mm in diameter. Catheters designed for peripheral vascular cases are also available. The carbide blade allows for excision of calcified plaque. Like the earlier DCA devices, the shaved plaque is stored in the nosecone of the device, allowing its retrieval. These atherectomy devices are the only available tools that allow for retrieval of human atheromatous tissue for research purposes. Another device is the Arrow-Fischell Pullback Atherectomy Device (Arrow Medical Devices Co, Reading, Pennsylvania, US).^17,18

Figure 14.2 The FoxHollow SilverHawk™ device.

Debulking with atherectomy, especially when aggressive, has been associated with a higher rate of vessel perforation (0.5–1.3%) than with ballooning alone, and there is also a small risk of aneurysmal formation during follow up, although this has not been associated with adverse clinical events. Whether this could be a problem if DCA were used before implantation of a DES (some of which are associated with negative vessel remodelling during follow up) is not known. Groin complications were slightly higher when using larger guide catheters.