Data from Machaalany J, Abdelaal E, Bertrand OF. Guide catheter selection for transradial PCI. Cardiac Interv Today. July/August 2013;1–5.

Bifurcational Lesions

Another potential limitation in the routine use of the 5F guiding catheters can occur when complex coronary bifurcations are encountered. Bifurcation disease accounts for about 15% to 20% of all coronary artery disease treated by percutaneous intervention²⁰ (see Chapter 18 on bifurcations). Whatever technique is used, bifurcation interventions present a lower procedural success, with poorer outcome and higher restenosis rate, than does nonbifurcation PCI. These findings have prompted, in the last few years, an intense research activity with the development of new dedicated devices such as side-branch dilatation balloons²¹ or especially designed stents that require a 6F or even larger guiding catheters.²² There are many accepted techniques currently used in the treatment of bifurcation lesions. The recommended treatment remains provisional stenting of the side branch as the gold standard with eventual kissing balloon dilatation as the final step. This requires the simultaneous advancement of two monorail balloons, which cannot be performed in a 5F guiding catheter unless the 0.010-inch guidewires and compatible balloon catheters are available.¹⁹ However, most recent data, while recommending the provisional approach, have shown no improvement of routine kissing balloon postdilatation on the patient’s outcome.²³ Hence, it should be recognized that using 5F for bifurcation allows for protecting the side branch with a guidewire, but if a more complex procedure is contemplated, the operator might prefer to upscale catheter size from the start.

Debulking Procedures

The mechanical properties of the arterial wall are critically dependent on the thickness of the wall and the characteristics of the intimal plaque²⁴; consequently, the balloon pressure necessary to achieve circumferential overstretch and a satisfactory lumen expansion is intrinsically dependent on the tissue property and wall thickness. Thick neointimal hyperplasia and severe coronary calcification contribute to the increase of the hoop stress to the point that even high-pressure noncompliant balloons might be insufficient to overcome the hoop stress and induct a satisfactory dilatation. Additional devices have been developed to overcome this limitation. Cutting balloons have been designed to relieve the vessel hoop stress by creating controlled small incisions in the vessel wall and present the practical advantage that they do not move during inflation due to the stabilizing effect of the blades. Cutting balloons present several advantages for the treatment of severe calcified lesions, allowing a larger luminal gain at lower pressure compared to balloon angioplasty alone and preventing the late recoil due to the incisions created by the blades.²⁵ The lack of clinical benefit observed in the early studies of cutting balloon versus conventional balloon angioplasty in de novo lesions has created skepticism on the potential mechanical usefulness offered by a focal concentration of force on the intimal plaque. However, cutting balloon may present advantages during the treatment of severe in-stent restenosis when thick neointimal hyperplasia and the stent itself contribute to increase the hoop stress.²⁶ Mehran et al.²⁷ demonstrated that when treating in-stent restenosis with balloon angioplasty, luminal gain is achieved by a combination of additional stent expansion and neointimal tissue compression through the stent, resulting in a displacement through the stent struts and compression of neointimal tissue. Although satisfactory initial clinical and angiographic results were obtained with balloon angioplasty, a significant early lumen loss was also observed shortly after in-stent restenosis treatment due to recoil and reintrusion of neointimal tissue in the lumen.²⁸ This early phenomenon possibly influences the long-term outcome after balloon angioplasty for in-stent restenosis, affected by a high re-restenosis rate.^29,30 Cutting balloons, compared with conventional balloons, present a significant advantage that the incisions of the microblades reduce the recoil of neointimal tissue into the lumen and allow greater stent expansion by reducing the hoop stress in the neointimal tissue and subsequent better extrusion of the neointima outside the stent and direct transmission of the expanding force of the balloon to the stent struts. Another potentially useful tool during treatment of severe calcified lesions is atherectomy. The most common atherectomy technologies are Excimer laser therapy and Rotablator. The Excimer laser therapy is based on the principle of photoablation converting occlusive material into microbubbles being immediately dissolved in the blood.³¹ The Excimer laser coronary ablation catheter is 6F compatible and its use has been successfully described both during the treatment of severe calcified lesions and in the acute ST-elevation myocardial infarction setting when a significant amount of thrombus burden is present.^32,33 Rotational atherectomy is a technique in which a small grinder is inserted into the coronary arteries to ablate the plaque. It is specifically effective in the treatment of calcified lesions because of its differential cutting mechanism. Differential cutting is a phenomenon by which soft tissues (such as the normal arterial wall) are deflected so that the grinder will not contact them during high-speed rotation, while hard calcified plaques are not deflected and can be ablated by the grinder.³⁴ The currently available rotational atherecthomy device is the Rotablator (Boston Scientific-Scimed Corporation, Natick, MA), equipped with a diamond particulate-coated, spinning burr available in various sizes for coronary use (from 1.25 up to 2.50 mm diameter). At this time, only the smallest burr (1.25 mm) can be used with 5F guiding catheters. Series using rotablator successfully to debulk lesions prior to stenting in 5F catheters have been reported, but most operators probably still prefer to use 6F guiding catheters in case of very calcified lesions and rotablator use. Alternatively, only smaller-sized cutting balloons can be used in 5F guiding catheters.

Chronic Total Occlusion

CTO affect almost 30% of the patients with coronary artery disease undergoing angiography,^35,36 and it remains a challenge for interventional cardiologists. Recent advancement in materials such as guidewires, microcathers, and crossing devices have increased the success rate of CTO percutaneous recanalization from 50%–60%^37,38 to 70%–80%,^39–41 with peaks above 90% for a few highly specialized centers.^42,43 The lack of a general consensus regarding the usefulness of CTO recanalization, together with the hardness of the procedure, has partially affected the development of CTO PCI in daily practice. Two large registries in the United States addressed the real benefit of CTO recanalization procedure on long-term survival, leading to conflicting results: negative the first⁴⁴ and positive only for left anterior descending artery recanalization the other.⁴⁵ However, they both included patients treated with plain old balloon angioplasty alone suffering from a high percentage of reocclusion. More recent studies, including only patients treated with stent implantation, showed that successful recanalization is associated with improved long-term survival and reduced need for surgical revascularization at follow-up compared to failed CTO procedure. Moreover, it has been recently shown that successful recanalization provided a significant improvement in quality of life, with less physical activity limitation, rarer angina episodes, and higher treatment satisfaction when compared to patients with failed procedure.⁴⁶

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