Abstract
Knowledge and application of eight basic principles and techniques are critical for safely and successfully performing chronic total occlusion (CTO) percutaneous coronary interventions (PCIs). First, CTO PCIs should be planned and not performed as ad hoc procedures. Second, dual (ipsilateral and contralateral) injections should be performed in nearly all cases. Third, the CTO should be carefully studied to formulate a detailed procedural plan. Fourth, dual arterial access with large bore sheaths is recommended in most cases for optimal support and simultaneous use of multiple pieces of equipment. Fifth, unfractionated heparin is recommended for anticoagulation. Sixth, techniques to enhance the guide catheter support are often needed, including use of anchor techniques and guide catheter extensions. Seventh, the trapping technique allows for equipment exchanges while securing distal guidewire position. Eight, the electrocardiogram and pressure waveform and constantly monitored for early detection of possible complications.
Keywords
Ad hoc, Anchor techniques, Angiography, Anticoagulation, Guide catheter, Guide catheter extensions, Monitoring, Technique, Vascular access, Wire trapping
3.1
Timing
In general, chronic total occlusion (CTO) percutaneous coronary interventions (PCIs) should not be performed ad hoc in order to :
- a.
Allow time for thorough procedural planning and preparation for both the operator and the cardiac catheterization laboratory staff, which is essential for success.
- b.
Minimize the amount of contrast administered and radiation dose.
- c.
Minimize patient and operator fatigue.
- d.
Allow time to collect sufficient information on the viability and/or the extent of ischemia of the territory supplied by the occluded vessel.
- e.
Allow for a detailed discussion with the patient and family about the indications, goals, risks, and alternatives (such as medical therapy and coronary artery bypass graft surgery) to the procedure. Risks that may be increased in CTO PCI compared with non-CTO PCI include radiation injury and perforation.
In some cases, however, ad hoc PCI may be the best option, such as in patients who present with an acute coronary syndrome due to failure of a highly diseased saphenous vein graft, in whom treatment of the native coronary artery CTO is considered to be the preferred treatment strategy ( Online Case 87 and 103 ). Also in patients with acute coronary occlusions resulting in cardiogenic shock, successful use of CTO PCI techniques can achieve urgent complete revascularization and help stabilize the patient’s hemodynamics.
3.2
Dual Injection
Dual injection angiography is of critical importance in CTO PCI. This is the simplest and most effective technique for increasing CTO PCI success rates and decreasing complications and should be performed in all patients with contralateral collaterals.
Even in antegrade-only cases, placing a safety workhorse guidewire in the donor vessel may stabilize the catheter, preventing disengagement of the guide catheter and allowing prompt treatment in case of a complication.
3.2.1
Why Is Dual Injection Important?
Dual injection provides the following benefits :
Before PCI
- a.
Nonsimultaneous, single-catheter injection often provides suboptimal visualization of the CTO segment and limited ability to assess both the proximal and distal cap and the distal vessel beyond the CTO due to collateral competitive flow ( Figs. 3.1 and 3.2 ). Occasionally, dual injection will reveal that the CTO is not a total occlusion, but rather a functional occlusion with a central patent channel ( Fig. 3.1 ). In other cases there may be more than one tandem CTO (see Online Case 6 ). Dual injections also provide a more accurate assessment of the true length of the CTO.
During PCI
- a.
Contralateral injection during CTO PCI allows visualization of the guidewire position during antegrade crossing attempts. If the guidewire is outside the vessel or in a side branch it can be repositioned before advancing equipment, significantly reducing the risk of perforation or other complications ( Fig. 3.3 ).
- b.
Even if there are ipsilateral collaterals at baseline, during CTO PCI the collateral flow direction and strength of flow can shift from one source to another ( Online Case 95 ) due to ipsilateral collateral damage, which can occur frequently in antegrade attempts, not allowing determination of distal guidewire position.
- c.
When using dissection/reentry techniques antegrade contrast injections may result in hydraulic enlargement of the subintimal space and reduce the likelihood of successful reentry ( Fig. 3.4 ). We recommend removing the injecting syringe from the antegrade guide manifold during dissection/reentry attempts to prevent inadvertent contrast injection and expansion of the subintimal space, as demonstrated in Chapter 5 , Fig. 5.15 .
3.2.2
Dual Injection Technique
- a.
Introduce the right coronary artery guide catheter first (before inserting the left coronary artery guide catheter) to allow for unimpeded torqueing necessary to engage the right coronary artery ostium, as well as to prevent guide–guide interaction with a left main guiding catheter during the procedure. In case of difficult cannulation of the left main, introducing a stabilizing guidewire into the right coronary artery can prevent disengagement of the right guide catheter.
- b.
Administer sublingual or intracoronary nitrates before injections to maximally dilate the vessels and help show collateral flow.
- c.
Use low magnification (13-inch instead of 8-inch) to enable visualization of the entire coronary circulation.
- d.
Do not pan the table to facilitate recognition of collaterals.
- e.
Obtain long cine acquisition to allow for the contrast to travel through the collateral vessels and fill the distal vessel.
- f.
Inject the donor vessel (vessel that supplies the territory distal to the CTO) first, followed by injection of the occluded vessel after collaterals have filled the distal vessel. To reduce radiation exposure the donor vessel can be injected before cine is recorded.
- g.
Avoid using a side-hole guide catheter on the donor side to achieve better distal opacification and decrease contrast volume.
- h.
Use of 8 French (Fr) guide catheters for angiography provides better filling of the vessel, improving visualization, especially of small collateral vessels. Too little volume and low rate of contrast injection can mask important information about the lesion and result in image artifacts.
- i.
In complex cases several contralateral injections might be necessary. The amount of contrast required may be decreased by inserting a microcatheter selectively into the donor branch and administering only 1–2 cc contrast for each image shot. This method cannot be applied in case of several collaterals due to the competitive blood flow from other branches.
- j.
As in all coronary angiography, looking at the electrocardiogram and pressure waveform before and after each contrast injection is a must. Electrocardiographic changes can provide early warning of an impending complication, such as ischemia during collateral vessel crossing. Injection in the setting of severe pressure dampening can cause severe coronary and/or aortocoronary artery dissection.
- k.
If collateral visualization is still suboptimal, a cine recording done at 30 frames per second (fps) can enhance visualization. This technique uses more radiation than 15 fps and should be used sparingly, remembering to reset the acquisition back to 15 fps.
- l.
Most interventionalists will use the right femoral artery to cannulate the right coronary artery and the left femoral artery to cannulate the left main . This is done to avoid confusion. If the right coronary artery is not being used the right femoral artery is often chosen for the antegrade guide and the left femoral artery for the retrograde guide. There is no magic about this choice but it is easy to remember and strongly recommended that it be done the same way every time. Advancing or pulling on the wrong wire or catheter can easily negate any progress that has been made.
One technique for simultaneous injection of both coronaries during the diagnostic angiogram without requiring a second point of access is to upsize the femoral arterial access point to an 8 Fr sheath. Two 4 Fr catheters can then be passed through a single 8 Fr sheath to allow simultaneous injection of both coronaries ( Figs. 3.5 and 3.6 ). However, coronary visualization may be poor with a 4 Fr catheter even with use of automatic injectors and bleeding may occur through the sheath’s hemostatic valve.
3.3
Studying the Lesion
3.3.1
How to Evaluate the Lesion
Spending enough time to study the CTO angiographic parameters will make the procedure easier and will increase the likelihood of success. Any other previous angiograms should also be located and reviewed carefully.
When? Before the case begins.
By whom? Ideally the films should be reviewed by the entire CTO team, including the physicians, technicians, and fellows.
How long? Usually 15–30 min per patient. This much time is necessary to fully understand the CTO anatomy and determine the best action plan. With each repeat viewing of the images, new anatomic information becomes evident; for example, the course of collaterals or the location of the proximal cap is better appreciated.
Which parameters should be assessed?
There are four key parameters that should be evaluated during the angiographic review ( Fig. 3.7 ) :
- 1.
Proximal cap and proximal vessel
- 2.
Lesion length and quality
- 3.
Quality of distal target vessel
- 4.
Collateral circulation
These parameters can help us understand: (1) where the CTO starts and what the vessel proximal to the CTO looks like; (2) the course and quality of the CTO segment; (3) the ending point of the CTO and the quality of the vessel distally; and (4) potential retrograde pathways for getting to the distal cap.
- •
Using slow replay and magnified views may help clarify the CTO vessel course and the collateral connections. In case of multiple collaterals a frame-by-frame replay can help determine the direction of flow in the branches of the distal vessel and identify the dominant collateral.
- •
Occasionally, tracing the collaterals backward may help identify their origin and course.
- •
Some image postprocessing techniques , such as color inversion and increasing the contrast, may help to discover usable collaterals.
- •
In some patients, preprocedural coronary computed tomography may help decipher the course of the occluded vessel and evaluate the presence and extent of calcification and tortuosity ( Section 3.3.6 ). This is especially helpful in patients with very long occluded segments. However, coronary computed tomography is not useful for assessing collaterals.
Why? To understand the CTO anatomy and collateral circulation, which enables the operator to map out all possible options for crossing the occlusion and create a strategic plan ( Fig. 3.8 ). Such procedural plans are often provided by proctors before planned cases.
3.3.2
Proximal Cap ( Fig. 3.9 )
3.3.2.1
Proximal Vessel
Diffusely diseased proximal vessels can cause pressure dampening upon guide catheter engagement. Pressure dampening may not cause ischemia in proximally occluded vessels supplying a small distal territory. Conversely, dampening in large vessels giving multiple side branches proximal to the occlusion could cause ischemia and/or hypotension, and may require intermittent guide catheter disengagement, use of a smaller guide catheter, or use of a guide catheter with side holes. Injection through a guide catheter with dampened pressure waveform could cause coronary and/or aortocoronary dissection ( Section 12.1.1.1.2 ) and should be avoided, often by removing the injection syringe ( Fig. 5.15 ). Pressure dampening can also predispose to air embolization and to thrombus formation within the guide catheter.
Careful wiring of diffusely diseased proximal vessels (usually using workhorse guidewires with standard tip bends) is critical to minimize the risk for proximal vessel dissection. A microcatheter is then advanced and the workhorse wire is exchanged for specific CTO wires with much smaller, CTO-specific bends, which can be more difficult to advance through larger vessels.
3.3.2.2
Side Branches
Side branches near or at the proximal cap may hinder antegrade wiring, since guidewires (especially polymer-jacketed guidewires) may preferentially enter those branches instead of engaging the CTO. Some of those branches could potentially be used for side branch anchoring to increase guide catheter support ( Fig. 3.10 , Section 3.6.5 ).
3.3.2.3
Proximal Cap Location
Understanding the start of the CTO (proximal cap) is critical for both success and safety. If the proximal cap is clearly defined and unambiguous, up front use of an antegrade approach is favored. CTOs with poorly defined, ambiguous proximal caps ( Fig. 3.11 ) may be best approached with a primary retrograde approach, or using advanced subintimal techniques, such as the “move the cap” techniques ( Section 9.1.4 ).
Multiple angiographic projections, including some unconventional ones, may be needed to clarify the location of the proximal cap ( Section 9.1.1 ); for example, the straight lateral projection for right coronary artery occlusions. In some cases, angiography alone may be inconclusive, but intravascular ultrasound can help elucidate the proximal part of the CTO ( Section 9.1.3 ). A full discussion of how to approach a CTO with an ambiguous proximal cap is presented in Section 9.1 .
3.3.2.4
Proximal Cap Morphology
Tapered proximal caps are more favorable than blunt caps, as they facilitate guidewire entry into the occlusion. The proximal cap is usually more resistant than the distal cap, likely due to exposure to arterial pressure. Severe calcification can make wire penetration challenging, requiring highly penetrating guidewires, such as the Confianza Pro 12, Hornet 14, and Astato 20.
3.3.3
Occlusion Length and Quality ( Fig. 3.12 )
3.3.3.1
Length
Lesion length is almost always overestimated with single injections, hence dual injections ( Section 3.2 ) are important for accurate estimation of the lesion length. Lesion length and quality assessment can also be performed using multiple detector computed tomography. Longer lesion length is usually associated with higher difficulty in crossing and lower success rates. A cutoff point frequently used is 20 mm : according to the hybrid algorithm ≥20 mm long lesions may be best approached with a primary dissection/reentry strategy (because subintimal guidewire entry is highly likely to occur), whereas <20 mm long lesions are usually first approached with antegrade wire escalation ( Chapter 7 ).
3.3.3.2
Quality
Intraocclusion calcification and tortuosity increase the difficulty of CTO crossing. Calcification ( Section 9.9 ) increases the likelihood of subintimal guidewire entry and may cause difficulty crossing with a balloon or microcatheter in case of successful guidewire crossing. Tortuosity increases the likelihood of guidewire exit and perforation, hence highly tortuous occlusions may be best crossed subintimally with a knuckled guidewire ( Section 5.4 ). The guidewire knuckle is less traumatic than the tip of a guidewire and more likely to remain within the vessel architecture, which is reflected in the motto, “trust the knuckle.” Occasionally, small contrast-filled islands can be discovered in the body of long occlusions. These islands are supplied by side branches communicating with collaterals and can be helpful for wire-based strategies to follow the track of the vessel and avoid wire exit from the vessel architecture.
3.3.4
Quality of the Distal Vessel ( Fig. 3.13 )
Evaluating the size and quality of the vessel distal to the occlusion is important for deciding on a procedural plan and estimating the likelihood of success. Large vessels distal to the CTO are associated with easier crossing and higher likelihood of success. Conversely, small, diffusely diseased distal vessels can be much harder to recanalize and are associated with lower procedural success rates, in part due to difficulty reentering in the true lumen if the antegrade guidewire crosses into the subintimal space. The size of the distal vessel may be small due to chronic hypoperfusion, but it can increase significantly both acutely and within a few months after successful recanalization. In some patients, the size of the distal vessel may be underestimated due to partial filling caused by competitive flow via ipsilateral and contralateral collaterals. Having access to prior films could greatly assist with determining the true size of the distal vessel.
Distal vessel calcification may hinder reentry attempts in the case of subintimal guidewire entry and/or predispose to perforation during or after balloon inflation or stent deployment. Very high-pressure postdilations should be avoided in heavily calcified vessels, especially with oversized balloons.
The morphology of the distal cap often cannot be visualized as clearly as the proximal cap because of lower perfusion pressure through the collaterals ( Fig. 3.14 ). Having a bifurcation at the distal cap makes CTO crossing harder, in part because if subintimal guidewire crossing occurs, reentry into the distal true lumen may result in loss of one of the branches. Such lesions may be best approached by a primary retrograde approach, or alternatively by performing double reentry into both branches of the bifurcation ( Section 9.6 , Online cases 5 , 7 , 8 , 12 , 25 , 34 , 45 , 49 , 64 , 80 ). Another option is to combine an antegrade approach for one of the branches with the retrograde approach for salvaging the other branch.
In patients with prior coronary artery bypass graft surgery the distal vessel may be distorted at the distal anastomotic site , as many times the bypass graft causes tenting of the native vessel at the anastomosis.
3.3.5
Collaterals
3.3.5.1
Source and Course of the Collaterals ( Fig. 3.15 )
- a.
Source
Collaterals may arise from the CTO artery itself, proximal to the occlusion (ipsilateral collaterals), or from another coronary artery (contralateral collaterals). These would include right to left collaterals or left to right collaterals. Aortocoronary bypass grafts (patent or occluded) are not true collaterals, but may still serve as retrograde conduits. For example, in patients with severely degenerated saphenous vein grafts (SVGs), recanalization of the native coronary artery provides superior short- and long-term outcomes as compared with treating the SVG.
- b.
Course (septal, epicardial, bypass grafts)
As their name implies, septal collaterals course through the septum, whereas epicardial collaterals course at the heart’s surface. Septal collaterals are preferred over epicardial collaterals, because they are safer to cross: septal collateral perforation rarely results in a complication, whereas epicardial collateral perforation can cause tamponade or localized chamber compression in patients with prior coronary bypass graft surgery resulting in a very difficult to manage scenario referred to as dry tamponade ( Online Case 43 , Section 12.1.1.2.5 ). Treatment of epicardial collateral perforations requires occlusion from both sides of the perforation for successful sealing. Both patent and occluded SVGs can be used for retrograde crossing. Retrograde crossing through internal mammary artery grafts is feasible ( Online Cases 29 , 37 , 46 , 50 , and 57 ), but may result in significant ischemia and hemodynamic compromise ( Online Case 46 ).
Not all epicardial collaterals are equal. For example, Mashayekhi et al. demonstrated that ipsilateral epicardial collaterals from acute marginal to acute marginal branch (Type B, Fig. 3.16 ) have high risk for perforation ( Fig. 3.17 ) and should not be used for retrograde crossing.
