Percutaneous Coronary Interventions of Chronic Total Occlusions

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10 Percutaneous Coronary Interventions of Chronic Total Occlusions

Percutaneous coronary intervention (PCI) of a chronic total occlusion (CTO), defined as a total occlusion (with TIMI grade 0 flow) of > 3 months duration, is one of the most technically challenging coronary subsets. Some lesions have minimal antegrade flow. These lesions, often called CTOs or functional CTOs, are not truly totally occluded and, by virtue of the small antegrade channel, have an increased probability of being recanalized antegradely. CTO composition is a function of age, with the older CTO typically being harder and more fibro-calcific. The rationale behind PCI of a CTO is to decrease ischemia and cardiac morbidity, improve left ventricular function and wall motion, avoid coronary artery bypass graft (CABG) surgery, improve quality of life, and possibly prolong survival.

PCI success rates for true CTOs are reported to be in the 50% to 80% range (compared to > 80%–90% for occlusions < 3 month-old CTO). Newer series with techniques described in this chapter describe success rates approaching 90% or higher. CTO PCI mortality rate is reported to be 0% to 2% and emergency coronary artery bypass surgery < 1% to 2%. Abrupt vessel closure following CTO PCI may occur in up to 5% to 10% of patients but is often clinically silent, depending on the collateral supply.

PCI Strategy

Prior to intervention, a formal strategy (“game plan”) should be devised (Fig. 10-1). By developing a game plan, overextending an already difficult procedure and increasing the risk of complications may be minimized. This plan must start with a decision as to whether the CTO is producing symptoms and/or ischemia, and if so, whether revascularization is actually required (as opposed to medical therapy). If revascularization is chosen, it must be decided whether the patient would be better served with CABG or PCI, as CTOs typically occur in patients with multivessel disease. If PCI is chosen, the next decision is whether the complexity is within the operator’s technical expertise or should be referred to a CTO super-specialist.

Figure 10-1 The algorithm considers treatment of the CTO only. It should be used as part of decision-making within the wider context of deciding on appropriate therapy considering the patient’s clinical syndrome, extent of coronary artery disease, left ventricular function, co-mordities, surgical risk, and other relevant factors to determine the best treatment strategy. If PCI is considered, the above algorithm is applicable.

The preprocedure plan must include the proposed limits of the attempt if success is not achieved, including the upper limits for contrast media, radiation exposure, and time on the cath table. The extent of the procedure may be influenced by the CTO characteristics, such as whether the lesion has favorable or unfavorable characteristics. Further, the plan should include a decision regarding the possibility of bringing the patient back for a second attempt and whether such an attempt would utilize a similar or a revised strategy, for example, a retrograde approach.

Favorable characteristics for the antegrade approach are shown in Figure 10-2 and listed in Table 10-1. Any combination of unfavorable characteristics significantly decreases the chance of success.

Figure 10-2 Morphology of total coronary occlusion: favorable and unfavorable morphology for procedural success.

(Modified from Safian RD, Freed M, Grines C, eds. The manual of interventional cardiology, 3 rd ed. Birmingham, MI: Physicians’ Press, 2001, p. 295.)

^{Table 10-1} Favorable and Unfavorable Characteristics for Antegrade Success for Chronic Total Occlusions

Favorable

1. Tapered occlusion, especially with a “bird’s beak” configuration

2. Short length (< 10 mm) occlusion

3. Absence of bridging collaterals

4. Absence of calcification

Unfavorable

1. Flush occlusions, particularly at side branches

2. Long occlusions

3. Presence of bridging collaterals

4. Heavy calcification

Stenting a CTO with a drug-eluting stent has been shown to improve acute and long-term results compared to balloon angioplasty and bare metal stenting. In CTOs that cannot be crossed antegradely, the technique of retrograde recanalization has been shown to be effective in some cases and will be discussed briefly.

Technical Considerations for CTO PCI

Angiography

Excellent vessel opacification and knowledge of the occluded segment length and course are important factors for PCI success. Visualization of retrograde collateral filling of the target vessel is often essential. Bilateral coronary angiography is an invaluable aid in many CTO cases (Fig. 10-3). Using the antegrade approach, opacification through the target vessel may be insufficient to visualize the CTO and the course of the potentially recanalized channel. The contralateral vessel injection may allow for visualization of the vessel segment distal to the CTO. Administration of intravenous nitroglycerin may further improve visualization.

Figure 10-3 Bilateral angiography shows the length and presumed course of the chronic total occlusion (CTO) in the right coronary artery.

Antegrade Approach

Guide and Support Catheters

A guide catheter with good backup is extremely important. The diameter of the guide remains an operator choice. In general, the greater the backup required and the amount of hardware to be introduced into the vessel, the larger should be the catheter diameter. Although stand-alone guidewire passage across a CTO may be effective, support for wire passage is usually required. Support for guidewire passage can be obtained with end-hole microcatheter, e.g., Corsair (Fig. 10-5B) or small-diameter (1.25–1.5 mm) over-the-wire (OTW) balloon catheter and will increase the chance for wire passage through the total obstruction. Wire passage through a CTO into the true lumen increases the success rate to nearly that of a non-CTO, that is, > 90%–95%. Although passage of the wire distally through the true lumen is another major key for success, subintimal wire passage can still be effective.

CTO Guidewires

Wire choice is another key element to treatment success. There is a very large portfolio of available wires. In general, guidewires may be classified as hydrophilic and non-hydrophilic; Table 10-2 lists a few examples of each. Each wire has its own unique combination of flexibility, trackability, torque transmission (or steerability), lubricity (or hydrophilicity), shaft support, wire tip load or strength, wire tip prolapsibility, radiovisibility, ability to shape and retain tip configuration, tip taper and thickness, and tactile feedback. The operator should become familiar with the properties of each wire that might be applied to a lesion so that a wire plan can be developed.

^{Table 10-2} Examples of Equipment for Recanalization of Chronic Total Occlusion Using the Antegrade Approach

Category	Example	Rationale for Use
Guiding catheter	Left: Amplatz, XB (Cordis), EBU (Medtronic), Voda (BSC) Right: Amplatz	Increased backup support
Guidewires	Hydrophilic wires: Fielder, Fielder XT (Asahi), Pilot 50 (Abbott)	Passage through microchannel
	Increased tip load: Miracle Bros 3-12 (Asahi), Confianza Pro (Asahi)	Passage through “hard” proximal cap
OTW balloon	1.25–1.5 balloon diameter (multiple companies)	Increase wire force to proximal capPredilation after crossing CTO
Microcatheter	Corsair (Asahi), FineCross (Terumo, Tokyo, Japan)	Provide increased wire force to proximal cap
Tornus		Enlarge lumen when balloon cannot pass lesion
Guide extender	GuideLiner (Vascular Solutions)	Increase backup support in tortuous, calcific, or difficult to CROSS lesions and vessels
Rotational atherectomy	Rotablator (Boston Scientific Corp.)	Enlarge lumen in undilatable lesion

There is no consensus regarding the first choice guidewire; some operators prefer a hydrophilic wire first in all cases, others prefer an individualized approach, and still others a stiff-tipped wire. The hydrophilic wire decreases frictional resistance, improving movement through the vessel. However, this type of wire may have a greater propensity to travel into the subintimal space or, if lodged, distally perforate a small branch. One commonly used strategy is the “wire strength step-up” starting with a wire with minimal tip strength, usually hydrophilic (e.g., Fielder, Pilot 50, or Fielder XT) and working up to moderate stiffness (e.g., Miracle Bros 3.0, 4.5, or 6 g) and if unsuccessful to a very stiff tip (e.g., Miracle Bros 12, Confianza Pro). Other operators individualize choice of the first wire depending on the angiographic characteristics of the CTO and the coronary anatomy.

A CTO may have a microchannel or soft elements that will allow a hydrophilic wire to slide through. On the other hand, and more frequently, the proximal CTO cap will be hard and require penetration with a relatively stiff wire. A combination of both stiff-tipped and hydrophilic wires may be needed to negotiate a long CTO.

Wire Movement Techniques

Three main wire movement techniques have been described: sliding, drilling, and penetrating. Sliding takes advantage of microchannels and soft areas in the lesion using a hydrophilic wire. Drilling is a form of controlled spinning whereby the wire tip is rotated to find the path of least resistance. The operator’s tactile sense may be helpful in this approach, but careful observation that the wire tip is freely moving is essential. Penetration uses shorter, more precise wire tip movements to penetrate the intraluminal plaque. No technique has obvious advantage over the others in preventing the wire in taking a subintimal course. In many CTO cases, a combination of movements and wires is used.

An important aspect of wire use is shaping the wire tip. It should be shaped to maneuver the expected vessel course and, at the same time, minimize the number and severity of wire bends to maximize transmitted force. A typical bend might be a 45-degree angle at the last 0.5 to 1 mm of the wire and a gentler secondary bend of 15 degrees 2 to 3 mm behind the distal bend. Each lesion requires individual evaluation in this respect.

When crossing CTOs, one should be sure that the guidewire is in the true lumen vessel rather than in the subintimal space. One technique to ensure proper position is to advance a small tracking or OTW balloon catheter, remove the wire, and inject contrast distally to verify the lumen. Injection should be weighed against the possibility of increasing the size of a dissection if the catheter is subintimal. Should the wire track subintimally, there are methods to recanalize the vessel, which will be discussed in subsequent sections.

Treatment After Wire Passage

Usually a balloon catheter can cross a CTO after wire passage. Balloon dilatation can then prepare the vessel for stenting. Occasionally a balloon cannot cross or, even rarer, the balloon crosses but the lesion is undilatable. When a balloon catheter cannot cross a lesion, a particularly useful device is the Tornus (Asahi Intec, Tokyo, JP; Fig. 10-5A), which acts somewhat like a screw to enlarge the channel. If that maneuver is ineffective, or if the amount of calcification is large, consideration of rotational atherectomy should be given if a Rotablator wire can pass through the total occlusion. The operator is sometimes faced with the decision of removing a non-Rotablator wire for a Rotablator wire; this may be necessary but the operator should appreciate that the life line, that is, the previously passed guidewire, has been lost during this interval.

Selected Devices and Techniques to Recanalize the CTO

PCI for CTO treatment is in rapid evolution. It is likely that new CTO techniques will increase the success rate to levels approaching that of non-CTO lesions. A full description is beyond the scope of this section, but a few of the more common devices and techniques are described. The reader is referred to the selected readings listed at the end of this chapter for more comprehensive descriptions of the technical aspects of PCI for CTO.

Double (or Triple Wire) Parallel Wire Technique

It is common that a guidewire passes subintimally during an attempted CTO crossing. One approach is to maintain the wire in place and use a second wire with an OTW balloon catheter to attempt to traverse the true lumen using the first wire as a marker of the subintimal space (Fig. 10-4A). A variant of this technique, known as the see-saw technique, utilizes an OTW catheter for wires, manipulating one wire and then the other, alternating their position between dissection plane and true lumen until one wire is able to cross the CTO intraluminally.

Figure 10-4 A, Example of double wire technique. The first wire was passed subintimal. It was left in place and a second wire was placed through the chronic total occlusion (CTO) in the true lumen. B, The anchoring technique is shown. With attempted passage of the stiff wire through the CTO using a microcatheter for increased support, the guide catheter prolapsed out of the vessel. A small balloon catheter was passed into a side branch proximal to the CTO, and the balloon was inflated. This prevented guide catheter retraction and allowed for more effective force transmission to the CTO cap.

Anchoring Technique

In some lesions where the proximal cap is hard, advancing the guidewire pushes the guide catheter out of the vessel (even with an excellent backup guide). A technique known as anchoring may be applied (Fig. 10-4B). A small angioplasty balloon is passed to a side branch proximal to the CTO and the balloon inflated. This maneuver will anchor the guide catheter in the coronary ostium. The force along the guidewire will be transmitted more effectively to the CTO and thus increases the chance of puncturing the cap or creating a subintimal wire dissection. The balloon may also be inflated proximal to the CTO, which will allow increased force transmission by the wire.

Open Sesame Technique

By placing a wire in a side branch proximally to a CTO, the configuration of the vessel at the CTO point may be modified, allowing a guidewire to penetrate the hard proximal cap.

Microchannel Technique

A stiff-tipped wire over an OTW balloon catheter or microcatheter is used to penetrate the proximal cap, as perpendicularly as possible. Nitroglycerin is instilled, followed by full-strength contrast to evaluate the existence of any microchannels. A hydrophilic wire can then probe the CTO for the presence of microchannels. This technique is recommended when the CTO is in a straight vessel segment, the proximal cap appears concave, and there are no adjacent side branches proximal to the CTO.

Mother-Child or Guide-in-Guide Approach

The mother-child technique utilizes one small-diameter guide catheter within a larger guide with passage of the smaller guide into the coronary near the occlusion. There is also a commercially available guide extender, the GuideLiner (Vascular Solutions), which may accomplish the same purpose (Fig. 10-5C). This technique allows for more efficient force transmission of the wire through the microcatheter or the OTW balloon catheter to the proximal CTO end, increasing the chance of puncturing the proximal cap.

Figure 10-5 Unique catheters for chronic total occlusion (CTO) percutaneous coronary intervention (PCI). A, Tornus (Asahi Intec, Tokyo, JP). B, Corsair microcatheter (Asahi). C, GuideLiner catheter (Vascular Solutions, Minneapolis, MN). D, Crosser (FlowCardia, Sunnyvale, CA).

Adjunctive Imaging

Intravascular ultrasound (IVUS) has been used to determine where the true lumen lies. When the CTO occurs at a side branch, the IVUS may be parked in the side branch, allowing the operator to visualize the origin of the CTO. If the wire enters the subintimal space, passage of the IVUS may provide visualization of the adjacent true lumen and allow for observing if the guidewire is, in fact, in the true lumen.

Coronary CTA has been used preprocedure to describe the vessel course and the severity of calcification. The use of these techniques is likely to undergo further refinement in the future.

Other Devices

The Crosser (FlowCardia, Sunnyvale, CA) is a mechanically driven catheter that uses vibrational energy to aid in crossing the CTO (Fig. 10-5D). The CrossBoss (Bridgepoint Medical, Plymouth, MN), a manually applied catheter with a slightly bulbous tip, has been utilized to cross a CTO intraluminally. It may also be used to traverse the subintimal space and, with the use of the Stingray balloon catheter and guidewire, allow guidewire lumen re-entry. Both the Crosser and CrossBoss have been utilized without a guidewire to cross the CTO.

Use of the Subintimal Space to Recanalize the CTO

The subintimal tracking and re-entry (STAR) and the related mini-STAR techniques have been used, primarily in the right coronary artery (> 80% of successful cases), for recanalization using the subintimal space. The hydrophilic wire is tracked subintimally, and the subintimal track is enlarged. In the STAR technique, the guidewire may track back into the lumen, frequently at a branch point, allowing for reconnection to the true lumen. As with the retrograde approach, this approach should be considered an advanced technique and be performed only by highly experienced interventionalists. The operator should appreciate that a 5% to 10% risk of perforation may occur with this technique.

A modification of the STAR technique, the mini-STAR, uses soft-tipped hydrophilic wires to cross the CTO subintimally and, by virtue of the wire type and tip bend, to re-enter the lumen distal to the CTO but more proximal than in the STAR technique.

There is a specialized OTW balloon catheter, the Stingray (BridgePoint Medical), which is used in the subintimal space to facilitate guidewire re-entry to the true lumen. The catheter is passed distal to the CTO after enlarging the subintimal space with a companion device, the CrossBoss, and the Stingray balloon inflated distally to the CTO. A specialized guidewire is passed to the balloon, exiting from one of two ports into the true lumen.

Common problems associated with the antegrade approach to CTO are listed in Table 10-3.

^{Table 10-3} Commonly Encountered Problems With the Antegrade Approach and Potential Solutions

Issue	Potential Solution
Cannot cross proximal cap	1. Use increased support guide catheter. 2. Pass microcatheter near proximal cap to increase wire force. 3. Use wire with increased tip strength or penetration power. 4. Use anchor technique. 5. Use open sesame technique. 6. Use mother-child deep intubation. 7. Consider other devices, e.g., Crosser, CrossBoss. 8. Consider retrograde approach.