Percutaneous recanalization of chronically occluded coronary arteries: Procedural techniques, devices, and results

Percutaneous coronary intervention (PCI) of chronically occluded coronary arteries represents the greatest technical challenge for the interventional cardiologist [1, 2]. Compared to intervention of nonoccluded stenoses, recanalization of chronic total occlusions (CTOs) requires more operator skill and procedural time, increases radiation exposure to the patient, physician, and catheterization laboratory staff, and consumes significantly greater resources. In no other lesion subset does the procedural success rate vary as much from physician to physician as with intervention in CTOs, and a definite learning curve exists in which technical success rates for individual operators continue to improve after the performance of hundreds of CTO procedures [3]. Moreover, until recently, the clinical benefits of CTO recanalization had not been clearly demonstrated, which, in concert with the technical complexity of the procedure, resulted in many patients with CTOs being either treated medically or referred to bypass graft surgery. There is now an increasing body of published evidence demonstrating that successful percutaneous recanalization of occluded coronary vessels subtending viable myocardium not only reduces angina and improves quality of life, but also improves left ventricular function and is strongly associated with enhanced survival [4-6]. Moreover, long-term patency and freedom from restenosis after successful recanalization of CTOs may be greatly enhanced by implantation of drug-eluting stents. As a result, tremendous interest has recently emerged among interventional cardiologists to learn the principles and develop the advanced skills required to maximize procedural outcomes in chronic coronary occlusions. In the first decade after the introduction of balloon angioplasty, technical success rates for PCI in true CTOs were achieved in only 40–57% of cases, reflecting the reliance on suboptimal guidewires, catheters, and dilatation equipment [7-10]. In the last 20 years, the procedural outcomes of intervention for CTOs have increased significantly as a function of improved guidewires and devices, as well as operator technique and experience, such that successful recanalization of true CTOs may now be achieved in approximately 80% of lesions [4, 5]. In order to achieve consensus on the techniques, methods, and devices required to maximize the likelihood of successful recanalization, an international group of 47 physicians from nine countries was convened in New York City in January 2004, representing many of the world's leading operators and thought leaders in the subspecialty of CTO intervention. Over a 2-day period, collective experiences were evaluated in detail and procedural outcomes were examined though a series of didactic lectures, roundtable discussions, breakout focus groups, and the performance of 14 live case demonstrations of complex angioplasty in occluded coronary arteries. Summarizing the lessons and guidelines generated from this summit, the present article will review the basic principles and advanced techniques required to develop expertise in CTO angioplasty and highlight the major innovations responsible for the current progress being achieved in the percutaneous revascularization of chronic total coronary occlusions. Appropriate patient selection is dependent on the experience of the operator in relation to the clinical and anatomic complexity of the CTO. Traditional predictors of lesion success have included shorter duration of the occlusion (< 3 months), functional total occlusions (those with TIMI 1 flow, which are no longer considered true CTOs), shorter lesion length, presence of a tapered or funneled stump, absence of a side branch at the occlusion site, minimal vessel and lesion tortuosity, absence of calcification, nonostial occlusion location, and a well-formed ipsilateral or contralateral collateral supply clearly delineating the vessel course distal to the occlusion [4, 11-16]. Conversely, the presence of bridging collaterals has traditionally been the strongest correlate of procedural failure [3, 4, 11, 12, 16]. However, with improvements in guidewire technology and procedural technique and experience, even bridging collaterals no longer represent the harbinger of procedural failure as once believed [2, 4, 10]. As a general rule, operators should begin with relatively straight-forward cases (e.g., short occlusions of limited duration, tapered stump present, and absence of bridging collaterals) and advance to more complex cases as they gain experience. For the most experienced CTO operators, the only near absolute lesion-specific contraindication is the absence of a visible distal vessel. Advance planning is necessary to optimize success rates of CTO angioplasty. The operator should review multiple projections of the occluded vessel in orthogonal projections frame by frame, as well as collateral vessels using contralateral injections when required to gain a complete understanding of the anatomy, the entry and exit points, the vessel course and side branches, as well as calcification (which serves as an important marker of vessel boundaries). If the CTO is old and bridging collaterals have formed, it is essential to differentiate the true lumen of a functional occlusion (with intracoronary microchannels, which may be crossed and dilated) from perivascular vasa vasorum or intravascular channels of a bridging collateral, which can easily be dissected or perforated with excessive wire manipulation. For each particular patient, the maximum allowable amount of radiographic contrast media should be defined prior to starting the procedure. To reduce the amount of dye, contralateral injections may be performed through an end-hole catheter inserted distally into the artery to perform superselective angiography. This technique can restrict the amount of contrast to less than 1 cc per injection. All patients undergoing PCI should be treated with at least 300 mg of oral aspirin at least 2 hr prior to the procedure. Because CTO angioplasty is rarely an emergent procedure, pretreatment with a loading dose of clopidogrel at least 6 hr before the procedure in anticipation of stent implantation during the procedure is recommended [17]. Procedural anticoagulation considerations are similar for PCI of nonoccluded stenoses, except that direct antithrombins and glycoprotein IIb/IIIa inhibitors are usually avoided because of the increased procedural risk of perforation. Glycoprotein IIb/IIIa inhibitors may be administered before angioplasty once the guidewire has successfully crossed the lesion and confirmed to be intraluminal. Similarly, the initial heparin bolus may be reduced to achieve an activated clotting time of approximately 200 sec until the guidewire has successfully crossed the occlusion, after which additional heparin should be administered before dilatation to achieve an activated clotting time of 250–350 sec (if a IIb/IIIa inhibitor is not utilized). Postprocedural heparin should rarely be administered following angioplasty, and the vascular sheath(s) removed as soon as the activated clotting time falls below 170 sec (or immediately postprocedure if a closure device is used). Aspirin (81 mg per day) should be prescribed after successful PCI of a CTO, and thienopyridine recommendations are the same as following PCI of a nonoccluded vessel (clopidogrel 75 mg per day for a minimum of 4 weeks after a bare metal stent, 3 months after a sirolimus-eluting stent, and 6 months after a paclitaxel-eluting stent) [18, 19]. Vascular access planning requires consideration of guide catheter support and the likelihood of requiring debulking devices or bifurcation stents, venous sheaths, or an intra-aortic balloon pump. Once the lesion is wired, difficulty passing a balloon across a CTO should be anticipated, necessitating excellent guide catheter support. Femoral artery access is preferred for CTO angioplasty by most operators, with utilization of 7–8 Fr guides for passive support, though 6 Fr catheters may be considered for short occlusions or by operators skilled with active guide manipulation. Larger guide catheters, however, provide the versatility to pass covered stent grafts more easily should a perforation occur, a complication that must be anticipated with PCI of CTOs [20, 21]. If a second angiographic catheter is necessary for contralateral injections, a 4 or 5 Fr catheter can be inserted into the contralateral femoral artery or either radial artery, though 4 Fr access from the ipsilateral groin may be an acceptable alternative by puncturing 1 cm medially and distally to the previously placed sheath [22]. Finally, the radial artery may be an acceptable alternative for CTO angioplasty by experienced operators in selected cases, especially when a guiding catheter no larger than 6 Fr is required, when the distal vessel is visible from ipsilateral collateral flow, when the location of the occlusion is mid or distal, and in the presence of otherwise favorable anatomy [23]. For the left coronary system, extra backup (EBU)-type guiding catheters (Voda left, extra backup, geometric left, left support) are preferable. Judkins-type guiding catheters, which typically preclude deep intubation, are associated with reduced success with hard fibrocalcific occlusions. For the right coronary artery (RCA), left Amplatz 0.75–2 shapes (which in general provide the maximal support) are preferred (especially with a superior or shepherd's crook takeoff), though hockey-stick shapes may be considered for the RCA with transverse or slightly superior takeoffs, or Judkins shapes for inferiorly oriented vessels. Typically, RCA guiding catheters should have side holes to allow perfusion of the sinus node and conus branches during tight seating of the guide. Aggressive manipulation of the guide catheter, or inadvertent deep intubation (which not infrequently occurs with the Amplatz shape) may dissect the ostial right coronary ostium (often requiring stenting), a complication that should be anticipated and recognized before guidewire removal. Guidewire crossing of the CTO is the most technically exacting phase of the procedure and the point at which success or failure is typically determined. There are three steps to crossing a CTO: penetrating the proximal fibrous cap, traversing the body of the CTO to reach the distal fibrous cap, and penetrating the distal fibrous cap. Optimal guidewire selection and technique are critical if procedural success rates are to be maximized. A vast array of guidewires are available, which may be used for CTO intervention, the most popular of which are listed in Table I. Wires designed for treating CTOs can be largely divided into two main groups: polymer-coated (hydrophilic or lubricious) guidewires and noncoated (nonlubricious) coil guidewires. Both groups may be further subdivided into those with nontapered tips (0.014″) and those with tapered tips (0.009″ to 0.010″). Each wire subgroup has inherent advantages and disadvantages when used for crossing CTOs, and each has its proponents recommending routine frontline use. We therefore present the consensus risk/benefit considerations when choosing each wire type. It is important for operators to become familiar with all wire types, but then to choose one or at most two wires for routine use. This is true whether one primarily uses conventional or hydrophilic wires. Most operators use nonhydrophilic-coated guidewires for CTO intervention. Conventional (nonhydrophilic-coated) wires are more controllable (and therefore less likely to dissect) and provide better tactile feel compared to hydrophilic wires. Noncoated coil wires tend to encounter more resistance inside the lumen than polymer-coated wires, but select coil wires (especially the Asahi Intec Miracle Brothers line; 0.014″ tip, available in "strengths" of 3, 4.5, 6, and, outside the United States, 12 g) and the Confianza (also known as the Conquest; 0.009″ tapered tip with 9 or 12 g force) have exceptional torque response even within a fibrocalcific CTO. The greater tactile feel of nonlubricious wires is especially important when attempting to penetrate the distal fibrous cap of a CTO and not create a false lumen. Notably, as the wire tip becomes stiffer, torque response increases, but less tip resistance is transmitted to the operator, making it easier to enter a false channel. Thus, lower-force wires are generally used initially (e.g., Miracle Brothers, 3 g), with progressive use of stiffer, more powerful wires if resistance to penetration is encountered. To minimize tip resistance and select small vascular microchannels within the CTO, some operators prefer tapered tip wires (e.g., the Guidant Cross-It series, which tapers to 0.010″ and comes in progressively greater strengths from 100 to 400, with the 400 corresponding to ∼ 6 g of force, and the Confianza). The technical success of these wires stems from their ability to engage and traverse through luminal microchannels within the occluded segment. In a contemporary PCI registry of 214 CTO revascularization attempts with tapered guidewires, overall technical success was achieved in 76% of patients; in the presence of a visible microchannel, however, the success rates ranged from 81% (incomplete microchannels) to 100% (microchannels with distal filling) [24]. Despite their benefit in penetrating resistant lesions, however, these needle-like tips can also easily dissect and perforate the vessel wall and thus should be used principally by experienced operators. The extreme lubricity of hydrophilic wires underlies both their strengths and weaknesses. Hydrophilic wires typically advance with minimal resistance and tactile feel, even down minute branches and false channels. These wires offer good maneuverability in tortuous vessels and, compared to coil wires, may be steered more easily in a true lumen immediately after a sharp bend. Conversely, in a true CTO, they are more likely to penetrate beneath plaque and dissect than noncoated wires, do not maintain their tip shape as well, and do not offer optimal tip control. Given the lack of tactile feedback, once in a false lumen a hydrophilic wire may be passed for long distances without resistance. This leads to a greater tendency to create large false channels that preclude success. Hydrophilic wires also tend to select small branches and perforate more frequently than noncoated wires. Such end capillary perforations may be difficult to manage, requiring coil embolization to seal [25]. Lubricious wires also more easily enter paralleling bridging collaterals and fragile vasa vasorum, the dilatation of which may result in perforation and tamponade. Finally, if the operator fails to recognize that a hydrophilic wire has entered a false passage or tiny branch and subsequently inflates a balloon, massive perforation, cardiac tamponade, and death can ensue. Therefore, it is imperative to visualize the distal course of hydrophilic wires in at least two orthogonal views and never inflate a balloon distally unless certain the balloon and wire are in the true lumen. Despite these caveats, a significant minority of operators select hydrophilic-coated wires as their wire of choice for CTOs because the reduced resistance to wire passage substantially accelerates the procedure (whether success or failure). The most commonly used hydrophilic wires currently are the Guidant Whisper (the floppiest lubricious wire), the Guidant Pilot (ranging in support from the 50 to the 200 version, with increasing stiffness), the Boston Scientific Choice PT and P2 and the stiffer PT and P2 Graphix, and the Cordis Shinobi (the stiffest hydrophilic wire, but also the one with the best torque response). As with noncoated wires, if hydrophilic wires are selected, initial attempts should begin with floppy wires, progressing to increasingly stiff wires if necessary. Operators who routinely use nonlubricious guidewires often find utility in hydrophilic guidewires when tortuous and/or fibrocalcific anatomy proximal to the occlusion is present. In such cases, the proximal passage may be simpler to negotiate with a hydrophilic wire, which can then be exchanged for a conventional wire for CTO crossing after passing an over-the-wire balloon angioplasty catheter to the point of the occlusion. Soft-tipped lubricious wires such as the Whisper (the least traumatic hydrophilic wire) may also be preferred when a faint channel is visible, consistent with an intracoronary microchannel that may allow easy access to the distal lumen. Care must be employed in this circumstance, however, not to create a false lumen, converting a simple case into a failure. Finally, the Confianza (Conquest) Pro is a hybrid 0.014″ wire that tapers to 0.009″ and is hydrophilic-coated except at the tip, thus reducing the friction as the wire shaft passes down the vessel and through the body of the occlusion while theoretically retaining tactile response at the distal end. Because of its combined stiffness, hydrophilic coating, and tapered tip, this powerful wire (which is available in 9 and 12 g versions) should be reserved for experienced CTO interventionalists. Once a stiff guidewire (whether noncoated or hydrophilic) has crossed the occlusion and has been passed into the distal vessel and the lesion crossed with an over-the-wire balloon dilatation catheter, it should be immediately withdrawn and a noncoated wire placed distally to minimize the risk of distal wire perforation or The most to CTO intervention is the use of nonhydrophilic-coated wires through a over-the-wire balloon angioplasty catheter (with balloon or an end-hole catheter (e.g., the Cordis catheter, or Boston Scientific The over-the-wire technique improves wire maneuverability and wire or tip In CTOs should be first with the same floppy guidewires used for PCI in nonoccluded As many as of CTOs that are believed to be or hard may be crossed with floppy wires (often by slightly the wire tip by the balloon catheter to the thus the risk of the proximal fibrous cap, however, may be difficult when the occlusion is requiring progressively stiffer wires. wire the course of the vessel and a curve of the wire tip are recommended to the proximal fibrous cap. A may be placed in the wire ∼ proximal to the to the reach of the guidewire if necessary without increasing the wire tip Once the wire through the proximal fibrous cap, it may be exchanged if for a wire with a slightly greater tip bend. the proximal cap is the wire must be passed through the body of the CTO to the distal fibrous cap, which typically requires experience and reliance on of the course of the as well as collateral of the distal vessel. calcification or occluded as guides to the vessel an in the the wire should be steered the curve to passage through an occlusion on a the proximal right coronary the wire to the of the curve typically in a The wire should be the curve of the vessel occlusions 3 typically at the end to a making penetration of the distal fibrous cap The optimal point for the penetration of distal fibrous cap is its the proximal channel often leads In the optimal point to to perforate the distal fibrous cap is usually on the and the of these lesions the technique to occlusions can be difficult to especially when a side branch at the of the CTO. The that plaque typically the side branch may the operator the true vessel Typically, however, the guidewire will often into the side and it may be difficult to penetrate the proximal fibrous cap. As a last dilatation of the artery with a angioplasty balloon in the side branch may the anatomy and to allow the wire to be into the main vessel and the necessary to enter the true lumen. If the wire a false lumen, attempts to it into the true lumen will often create an that can of the true lumen and of the proximal fibrous cap, making lumen Moreover, and wire the which reduces wire resistance and may create a false that the true lumen has been Once the wire has entered a false lumen, the technique is the best to the true lumen while the risk of and perforation. In the when a wire is to have entered a false lumen, it is left in to the and a second stiffer and often wire with a slightly and by an over-the-wire balloon catheter is passed the same to the first wire, with to wire the first wire in also the of in the vessel and a marker to guide the second wire the of a or more wires may be In a the both wires are by over-the-wire angioplasty catheters and are used to the occlusion to find the true lumen. The A Miracle 12 g wire a at the of the distal right coronary The wire is left in as a marker and a second wire in this with a slightly and curve is passed in and then steered the of an occluded right coronary The first wire has entered a false lumen. the a second wire by an over-the-wire balloon is to enter the true lumen. In cases, the CTO be successfully crossed from an but the true lumen can be from a a large collateral vessel (e.g., a or a bypass graft that with the distal vessel. The wire is into the distal vessel the occlusion and then steered to the end of the distal fibrous cap, which is often more easily from The wire can either as a marker or create a channel that can then be used to passage of a second wire in an the CTO can be through the collateral channel or a have that passage of a guidewire into a is a to recanalization of CTOs can differentiate a true lumen from a false lumen by side branches (which only from the true and and media (which the true lumen, but not the false Similarly, can when the guidewire has the true lumen from a false lumen. A case with a wire entry by is in have also that the major that it is difficult to penetrate the distal cap into the true lumen is that the guidewire to into a false not because of calcification or in contrast to the proximal entry that is often in a chronic total occlusion of the left coronary The short guidewire was used first and was passed into a false lumen. The second wire wire to the is in the true lumen. was performed this and of the proximal and of occlusion, demonstrating that the wire is in the true lumen. and The false lumen by first wire is the of media The catheter is to be in the true lumen as by a side branch the proximal and distal fibrous of a chronic total occlusion. and views at both of a chronic total occlusion of at the ostium of the left artery after with a A fibrous cap is at the proximal end of the occlusion. calcification and a fibrous were at the distal cap, it was difficult to penetrate into the true lumen at the distal end of occlusion as the guidewire frequently the distal cap, a false lumen. can also be in the of a CTO when the ostium is occluded or the entry is otherwise In such cases, the catheter can be inserted into a proximal side branch to the location of the occlusion and guide passage of the of this use of to a CTO is in of the utility of in the of an ostial occlusion. occlusion of the of an branch of the The entry point is with at a superior point demonstrating the absence of a side slightly demonstrating the occluded branch by an the wire the catheter placed in the branch in the left a second wire is used to the occlusion. is used to guide the of the wire to the of the occlusion. the wire is passed distally through the body of the occlusion. The first to a CTO should be with an balloon dilatation catheter with a tapered tip and a lubricious to crossing even long occlusions. The catheter should and have an excellent from balloon to operators use an end-hole catheter which slightly better but may not as and of course the dilatation function of a balloon angioplasty orthogonal projections and contralateral injections, it is whether the distal wire is in the true lumen, the balloon may be passed across the occlusion to the then withdrawn and If the distal vessel is not the balloon may be passed across the CTO, the guidewire and a small amount of distally the guidewire lumen. Such distal injections should be reserved as a procedure of last however, as they will either of the catheter or a typically the the occlusion is crossed and with the over-the-wire catheter, the true of the CTO may be and balloon angioplasty and stent implantation performed with It should be however, that in the distal vessel is after CTO recanalization, often necessitating large and of intracoronary or other the true vessel is not and/or the CTO with a balloon angioplasty catheter may be difficult and, in to of cases, typically to the presence of fibrocalcific especially when guide support is that may be considered for such difficult use of larger and more guiding deep guide catheter introduction of a second wire into a branch proximal to the occlusion to the support of the guiding catheter, or in the true lumen to the first wire to the of the wire channel which it is of an angioplasty balloon either in the main vessel or in a side branch to the guide and use of debulking most have not a for debulking of CTOs to reduce restenosis or may allow balloon passage or of otherwise CTOs is best the 0.014″ guidewire with the catheter using and an is not required as a is in this is an excellent alternative if a is not of this however, requires the occlusion with a 0.009″

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