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

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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