Abstract
The retrograde approach to chronic total occlusion (CTO) crossing differs from the antegrade approach because the occlusion is approached from the distal vessel. The retrograde approach can be divided into ten steps. First, a decision is made to proceed with retrograde crossing as primary strategy or after failure of antegrade crossing. Second, a collateral vessel is selected, and third, a microcatheter is advanced to the collateral vessel. Fourth, the collateral vessel is crossed with a guidewire, and fifth, guidewire position within the distal true lumen is confirmed. Sixth, the collateral is crossed with the microcatheter. Seventh, the CTO is crossed using various techniques that may include dissection and reentry. Most commonly the reverse controlled antegrade and retrograde tracking and dissection technique is used. Eighth, the retrograde guidewire is externalized in some cases. Ninth, the CTO is treated with balloons and stents. Tenth, the retrograde equipment is removed.
Keywords
Bypass grafts, Chronic total occlusion (CTO), Collaterals, Dissection, Epicardial, Equipment, Guidewire externalization, Reentry, Retrograde, Reverse controlled antegrade and retrograde tracking and dissection, Septals, Stents
6.1
Historical Perspective
The retrograde technique differs from the standard antegrade approach in that the occlusion is approached from the distal vessel, advancing a wire against the original direction of blood flow (i.e., retrograde). The guidewire is advanced into the artery distal to the occlusion through either a bypass graft or through collateral channels. This approach differs from the antegrade approach, in which all equipment is inserted only proximal to the occlusion and travels in the same direction as the original arterial flow (i.e., antegrade).
The retrograde chronic total occlusion (CTO) percutaneous coronary intervention (PCI) technique was first described by Kahn and Hartzler in 1990, who performed balloon angioplasty of a left anterior descending artery (LAD) CTO via a saphenous vein graft (SVG). In 1996 Silvestri et al. reported retrograde stenting of the left main artery via an SVG. In 2006 Surmely, Tsuchikane, Katoh et al. first reported retrograde crossing via septal collaterals, starting the modern era of the retrograde techniques through septal and epicardial collaterals as well as through arterial bypass grafts. The introduction of specialized equipment and further refinements of the technique started in Japan with rapid adoption both in Europe and in the United States.
6.2
Advantages of the Retrograde Approach
Crossing in the retrograde direction can sometimes be easier than antegrade crossing because the distal cap:
- 1.
Is usually easier to enter than the proximal cap, as it is more frequently tapered.
- 2.
Is often softer than the proximal cap, likely because of exposure to lower filling pressure.
- 3.
Is less frequently anatomically ambiguous.
Moreover, the antegrade approach may not be feasible or desirable in some CTOs, for example ostial and stumpless CTOs; CTOs with ambiguous proximal cap; CTOs with bifurcation at the distal cap; long and tortuous CTOs; CTOs previously attempted and failed antegradely; failed CTOs with extensive dissection; or CTOs with diffuse disease distal to the occlusion. In cases where antegrade wiring is challenging because of ambiguous course, the retrograde wire can help direct the antegrade wire and ensure that the latter is in the structure of the vessel proper. Retrograde CTO PCI might also be advantageous in patients with severe renal insufficiency and clear retrograde channels, because most steps required to complete the retrograde approach require limited contrast injection.
6.3
Special Equipment
In addition to the standard equipment needed for the antegrade approach, the retrograde approach requires specialized equipment: short guides, specialized microcatheters (150–155 cm long), and long guidewires for externalization, such as the R350 and RG3 wires, as described in Chapter 2 .
- 1.
Short guide catheters and guide catheter extensions
The standard guide catheter length is 100 cm (shaft length, although the length from the hub to the guide tip is approximately 106 cm). If standard guide catheters are used for the retrograde approach, equipment may not be long enough to reach the lesion retrogradely ( Online Case 99 ): the retrograde microcatheter might not reach the antegrade guide catheter, and wires advanced retrogradely may be too short to be externalized, especially with retrograde crossing through epicardial collaterals or bypass grafts. Utilizing a shorter guide catheter extends the reach of balloons, wires, and microcatheters advanced retrogradely, as the length of the catheter outside the body has been decreased by the shorter guide length. Shorter guide catheters (usually 90 cm guides are used) are commercially available, but if they are not locally available, any guide can be shortened using an interposition segment of sheath, as described in Section 2.3.2 . Another option is to use a guide catheter extension deeply intubated into the CTO target vessel, which is especially useful for retrograde crossing through epicardial collaterals or (left or right) internal mammary artery grafts.
- 2.
Microcatheters
Several microcatheters are available for the retrograde approach, such as the Corsair, Caravel, Turnpike, Turnpike LP, Finecross, Nhancer ProX, and Micro 14 ( Section 2.4 ). Only long (150 cm, except for the Nhancer and Micro 14, which are 155 cm long) microcatheters should be used for retrograde crossing. Larger microcatheters, such as the Corsair and Turnpike, facilitate collateral crossing, providing collateral dilation at the same time, and have good penetration power into the distal cap, yet may be challenging to deliver through small and tortuous collaterals. Lower profile microcatheters, such as the Caravel, Turnpike LP, Finecross, and Micro 14, may be easier to deliver, especially through small caliber epicardial collaterals, but provide less support for crossing complex (such as heavily calcified) lesions.
- 3.
Externalization guidewires
Dedicated externalization guidewires are currently available (RG3 and R350) ( Section 2.5.6 ) and should be used for externalization whenever possible. These wires are long (330 and 350 cm, respectively), thinner than standard guidewires, and have hydrophilic coating over more than half of their shafts. The tip of the wire should not be bent, to facilitate antegrade equipment loading after externalization.
If a dedicated externalization guidewire is not available or cannot be used (e.g., when the guidewire crosses into the antegrade guide catheter but the microcatheter cannot be advanced into the antegrade guide catheter), a Rotawire (BostonScientific) or Viperwire Advance (CSI), which are 330 and 325 cm, respectively in length, can be used although they are delicate and prone to kinking. A standard length (300 cm) guidewire can often be used for externalization, especially if short guide catheters or guide catheter extensions are being used. However, externalization of standard guidewires is more challenging and requires more time and more force, potentially leading to compression of the heart with hypotension, bradycardia, and occasionally asystole. Lubricating the microcatheter with Rotaglide may facilitate externalization of such wires.
- 4.
Collateral crossing guidewires
Preferred wires for septal crossing are composite core soft guidewires (such as the Sion, Suoh 03, and Samurai RC) or soft, polymer-jacketed wires such as the Fielder FC, Fielder XT-R, and Sion Black ( Section 2.5.4 ). The best tip bend is very short (1 mm) and quite shallow (20–30°, although some operators use 90 degrees bends) to allow for tracking very small, tortuous collaterals.
6.4
Step-by-Step Description of the Procedure
Goal
Decide when the retrograde approach should be used. If retrograde crossing is selected the activated clotting time (ACT) should be kept >350 s.
How?
- A.
Appropriate collaterals exist.
And
- B.
There is local experience and expertise in the retrograde technique.
And
- C1.
The antegrade approach fails.
Or
- C2.
As the initial crossing strategy (primary retrograde) in the following cases:
- 1.
Ambiguous proximal cap or stumpless occlusions.
- 2.
Ostial occlusions.
- 3.
Long occlusions.
- 4.
Severe proximal tortuosity or calcification.
- 5.
Small or poorly visualized distal vessel.
- 6.
CTO vessels that are difficult to engage, such as anomalous coronary arteries.
- 7.
Occlusion involving a major distal bifurcation.
- 1.
Goal
Select the collateral(s) that will be used for the retrograde approach.
How?
The usual preference order for selecting a retrograde collateral channel is bypass graft, septal, then epicardial. Given high risk for dissection causing ischemia and hemodynamic compromise (see Online Case 46 ), left internal mammary artery grafts should only be used as the last resort for retrograde access (see Online Cases 29 and 46 ) with strong consideration of using prophylactic hemodynamic support. The advantages and disadvantages of each collateral channel are shown in Fig. 6.1 . The classification and optimal angiographic views for evaluating collateral vessels are discussed in detail in Section 3.3.5 .
Bypass grafts Online cases 10, 16, 29, 50, 57, 61, 81, 85, 87, 96, 102, 103 are large and easy to wire ( Fig. 6.2 ), but are infrequently available: they were used in 19% of retrograde CTO PCI in prior coronary artery bypass graft (CABG) surgery patients in one series. Although CABG surgery causes scarring of the pericardium it does not eliminate the likelihood of free pericardial effusion (or even worse, loculated pericardial effusion ) and tamponade in case of perforation during CTO PCI. Even acutely occluded SVGs (Online Cases 87 and 103 ) can serve as conduits to the distal arterial segment of chronically occluded native coronary arteries. Bypass grafts may tent the vessel to which they are anastomosed, potentially changing the expected course of the native coronary vessel.
There is currently controversy as to whether patent but degenerated SVGs used as retrograde conduit for CTO PCI should be coiled after successful completion of CTO PCI. Coiling could stop competitive flow through the native stented segment and possibly decrease the risk of subsequent stent occlusion or thrombosis (see Online Case 10 ).
Retrograde crossing via internal mammary artery grafts, such as the left internal mammary artery (LIMA), should be done with extreme caution and only by experienced retrograde operators, as it can cause hemodynamic collapse, even without injury of the graft, often due to straightening of the graft tortuosity by the wires and microcatheters (see Online Cases 29 , 37 , 46 , 50 , 57 ).
Wiring of septal collaterals ( Figs. 6.3 and 6.4 ) is preferred over wiring of epicardial collaterals, mainly because the risk of tamponade following channel perforation is substantially lower in septal collaterals as compared with epicardial collaterals. Injury or perforation of a septal collateral is less likely to cause acute myocardial infarction, myocardial hematoma, or tamponade compared with perforation of an epicardial collateral. Treatment of collateral perforation is presented in Chapter 12 . In addition, septal collaterals are usually less tortuous than epicardial channels and are less likely to cause ischemia during crossing, as multiple septal collaterals usually exist.
Selecting the shorter collateral is preferred because (1) it provides better support and (2) it minimizes the risk of not being able to reach the target lesion. However, if a septal collateral enters the vessel close to the distal cap, there may not be enough space to allow for delivery of a wire and a microcatheter into the distal true lumen; using a collateral that enters the vessel more distally is preferred in such cases. Collaterals with corkscrew morphology and >90 degrees angle with the recipient vessel may be challenging or impossible to wire, whereas nontortuous, large collaterals (CC1 or CC2 by the Werner classification as described in Section 3.3.2.1 ) are the easiest to wire. Often invisible collaterals (CC 0 by the Werner classification) can be successfully crossed using the surfing technique.
It is generally easier to advance a wire through a septal collateral from the LAD to the right coronary artery (RCA) than from the RCA to the LAD, because the RCA ends of septal collaterals usually have more acute turns at their origins and more tortuosity in their lower courses ( Fig. 6.4B and C ).
Finally, epicardial collaterals ( Fig. 6.5 ) (see Online Cases 13 , 37 , 38 , 54 , 56 , 62 , 63 , 64 , 88 , 93 , and 97 ) are the least preferred for retrograde CTO PCI, because they are usually more tortuous than septal collaterals and their perforation can lead to rapid tamponade, especially in patients with an intact pericardium. In patients with prior CABG surgery, epicardial collateral perforation can lead to hematoma and localized tamponade, not accessible with pericardiocentesis ( Section 12.1.1.2.5 ). Moreover, if epicardial collaterals are the only source of collateral blood flow and they become occluded during CTO PCI, acute ischemia and myocardial infarction may occur. Sometimes, due to severe tortuosity the control of the guidewire can be limited and advancement challenging or impossible (see Online Case 62 ). Despite these limitations, with increasing experience and improvements in the retrograde equipment (wires and microcatheters), the use of epicardial collaterals (including ipsilateral epicardial collaterals ) has been increasing.
In patients with ipsilateral collaterals (such as septal collaterals from the proximal into the distal LAD– Figs. 6.6 and 6.7 and Online Case 51 ; or diagonal or obtuse marginal left-to-left collaterals– Online Cases 56 , 66 and 88 ; or right-to-right atrial collaterals- Online case 101 ) dual injection may not be required.
- •
A special challenge with ipsilateral collaterals is that the retrograde wire often takes a fairly sharp turn to return into the proximal vessel, which can lead to kinking and difficulty advancing equipment, or more importantly, to collateral rupture (which may occur more frequently with ipsilateral than contralateral collaterals).
- •
If the CTO is successfully wired through the collateral, then a second ipsilateral guide catheter may be beneficial for trapping or externalizing the wire, because if the retrograde wire is inserted into the antegrade guide catheter, equipment delivery is more difficult through the same guide catheter. Equipment delivery is easier using a ping-pong technique, in which engagement of the target vessel is alternated between the two guide catheters ( Fig. 6.8 ) ( Online Case 51 and 101 ).
Figure 6.8
Example of the ping-pong guide catheter technique for retrograde chronic total occlusion (CTO) percutaneous coronary intervention via an ipsilateral collateral.
Online Case 101 Coronary angiography demonstrating a proximal right coronary artery CTO due to in-stent restenosis ( arrows , panel A), with an ipsilateral atrial collateral ( arrows , panel B). Retrograde CTO crossing with wire exiting into the aorta (panel C) followed by successful snaring through a second guide catheter (panel D) and stenting (panels E, F) using the two guide catheters in a ping-pong fashion.
Reproduced with permission from Brilakis ES, Grantham JA, Banerjee S. “Ping-pong” guide catheter technique for retrograde intervention of a chronic total occlusion through an ipsilateral collateral. Catheter Cardiovasc Interv 2011; 78 :395–9.
Invisible Collaterals
Some patients may appear to have only epicardial collaterals, but if those collaterals become occluded, then septal collaterals may also appear (recruitable collaterals). Selective injection, the so-called tip injection, of the septal perforator branches (through an over-the-wire balloon, or through a microcatheter) may also allow visualization of previously invisible collaterals. Another option for crossing invisible septal collaterals is with the surfing technique, in which septal collaterals are probed and crossed without contrast injection. This technique increases the success rates of collateral crossing, but has the limitation that sometimes the collaterals are too small to be tracked by microcatheters.
Rarely collateral vessels may not be apparent during diagnostic angiography. For example, an isolated conus branch can occasionally supply collaterals to an occluded LAD territory and has been used for retrograde PCI or for facilitating antegrade crossing (see Online Case 2 ) in such cases.
Goal
Advance a wire and microcatheter into the target collateral vessel.
How?
- A.
Use a workhorse guidewire to minimize the risk for proximal vessel injury.
- B.
Larger, double bends on the workhorse guidewire are often needed to get to the collateral ( Fig. 6.9 ). After microcatheter advancement the wire is exchanged for a collateral crossing guidewire with a small distal bend.
Figure 6.9
Illustration of double bend wire shaping for entering a septal collateral.
- C.
For collaterals with an acute takeoff from the parent vessel consider using the Venture catheter ( Fig. 6.10 ), an angulated microcatheter (such as the SuperCross), or a dual lumen catheter (such as the Twin Pass Torque) to enter the collateral.
- •
Caution : Wire trapping for removal of the over-the-wire Venture catheter without losing wire position cannot be performed in <8 Fr guides (due to large profile of the Venture catheter).
Figure 6.10
Illustration of septal collateral branch wiring using a Venture catheter.
- •
What Can Go Wrong?
- A.
Injury (such as dissection) of the donor vessel , while trying to enter the collateral (see Section 12.1.1.1.1 ) ( Online Case 97 ). This can be a catastrophic complication, leading to rapid hemodynamic collapse, and requires immediate treatment (usually with stenting). Stenting of proximal vessel lesions should be considered prior to retrograde crossing to minimize the risk of proximal vessel dissection (jailing of a septal collateral usually allows wiring of the collateral branch and subsequent equipment delivery through the stent struts). Also use of a safety wire in the donor vessel can facilitate donor guide catheter engagement, straighten the artery potentially facilitating wiring of collaterals, and provide access to the vessel in case of a complication, such as dissection or thrombosis ( Online Case 22 ).
Goal
Cross the collateral with a guidewire.
How?
The technique varies depending on the type of collateral used (septal, epicardial, or SVG).
Step 4a Septal Collateral
See Online Cases 5 , 7 , 9 , 12 , 17 , 18 , 20 , 22 , 23 , 28 , 31 , 32 , 33 , 36 , 40 , 41 , 42 , 43 , 44 , 53 , 57 , 58 , 59 , 60 , 64 , 65 , 69 , 70 , 71 , 74 , 77 , 78 , 79 , 84 , 90 .
Once the microcatheter is inserted into the septal collateral ( Fig. 6.11 ), the workhorse wire is removed and exchanged for a wire with a low tip load that is highly torquable, most commonly a Sion wire. For septal crossing the wire is shaped with a very small (1–2) mm 30 degrees bend at the tip using the wire introducer. This shape allows tortuosity to be navigated and the wire to be directed away from small side branches.
There are two techniques for subsequent crossing: surfing and contrast-guided.
- 1.
Introduced by Dr. George Sianos.
- 2.
The guidewire (Sion is more commonly used currently) is advanced rapidly with simultaneous rotation until it either buckles or advances into the distal target vessel. If the wire buckles it is withdrawn and redirected.
- 3.
Septal surfing can be a very efficient crossing method.
- 1.
Surfing should never be done in epicardial collaterals, because of high risk for perforation.
- 2.
If the wire repeatedly takes the same unsuccessful course, retract further back before readvancing to select alternate route.
- 3.
Do not push hard and stop immediately when you feel resistance! Force will increase the risk of collateral injury without increasing crossing success.
- 4.
The odds of successful wiring are usually higher in proximal, straighter septals.
- 5.
Septal collaterals are usually straight in their upper half (LAD side), then bow toward the apex and turn again into the posterior descending artery ( Fig. 6.12 ).
Figure 6.12
Right anterior oblique caudal view of septal collaterals.
Therefore right anterior oblique (RAO) cranial is the best projection for initial wiring, and RAO caudal for entering into the posterior descending artery.
- 6.
Septal collaterals from the most proximal LAD tend to connect to the right posterolateral branch, whereas more distal septals connect to the posterior descending artery. Very distal septals may connect to a right ventricular branch.
- 1.
Use a 3 mL luer-lock syringe with 100% contrast. Medallion syringes (Merit Medical) are more resistant to breaking during forceful injection.
- 2.
First aspirate until blood enters the syringe (to avoid air embolization and to ensure that the microcatheter is not against the septal collateral vessel wall). If no blood can be aspirated pull back the microcatheter for a short distance until blood can be aspirated. This prevents air embolism and reduces the risk of hydraulic dissection.
- 3.
Perform cine-angiography while gently injecting contrast with the 3 mL syringe.
- 4.
Flush the microcatheter before reinserting the guidewire (to minimize subsequent stickiness).
- 5.
If a continuous connection to the distal vessel is observed, reattempt crossing through that connection.
- 6.
Do not pan to avoid change in collateral road mapping.
- 7.
Consider RAO caudal projection to evaluate the length and tortuosity of the distal part of the septal collateral. Also left anterior oblique projections can be useful if there is limited progress with the RAO views.
- 8.
A description of various types of septal collaterals is shown in Fig. 6.13 .
Figure 6.13
Overview of septal collateral anatomy. Three types are described.
(I) Proximal Septal: They often connect to the posterolateral system and have a partial epicardial course. (II) Mid Septal: They generally connect to the PDA and are often tortuous before entering into the posterior descending artery. (III) Distal Septal: Attention is needed because crossing can create high shear stress during externalization.
Courtesy of Dr. Kambis Mashayekhi.
- 9.
Flush the catheter with saline to avoid wire sticking. The remaining contrast will exit the microcatheter before the saline completely flushes the lumen. This is an extra collateral shot that can be used for viewing the collateral in another projection during cine-angiography.
What Can Go Wrong?
- 1.
Collateral dissection (in most cases further attempts to cross may be performed via a different collateral).
- 2.
Collateral perforation ( Section 12.1.1.2.5 ), which is nearly always benign and only causes localized staining; however, there are reported cases of septal hematoma formation and/or perforation into the pericardium causing hemodynamic compromise.
- 3.
Guidewire entrapment: to prevent this complication do not allow big (>1.5 mm) and acute (>75 degrees) bends to form at the tip of the guidewire during attempts for retrograde crossing of the septal collateral. The wire should not be overtorqued by continuous spinning in one direction.
- 4.
Microcatheter tip fracture and entrapment. If the tip of the microcatheter is stuck avoid turning it multiple times; instead withdrawal, followed by rotation is preferable.
Step 4b Epicardial Collateral
See Online Cases 13 , 36 , 37 , 38 , 54 , 56 , 62 , 63 , 64 , 66 , 88 , 93 , 97 , 101 .
- 1.
Perform injection through a microcatheter to visualize the collateral vessel course. Be certain that the microcatheter is not wedged (blood aspiration through microcatheter) and inject gently to avoid collateral damage.
- 2.
The Sion Black, Suoh 03, Sion, and Fielder XT-R wires perform best in crossing epicardial collaterals.
- 3.
Advance the wire first, then follow with the microcatheter—never let the microcatheter advance ahead of the guidewire.
- 4.
The microcatheter will straighten tortuosity and allow subsequent advancement.
- 5.
Rotate the wire (do not push) in tortuous segments. Crossing may be easier during diastole, when the angle between collateral turns is wider ( Fig. 6.14 ).
Figure 6.14
Illustration of changes in epicardial collateral channel angulation during the cardiac cycle.
In tortuous epicardial channels, wire crossing through the spiraling segments is the key to success. When the tip gets caught in the curve, quick torque of the wire tends to slide a little on a wider angle in diastole. Therefore, timely torqueing is necessary to go through the spiral segment of the channel.
- 6.
Once the wire reaches the distal true lumen it is advanced to the distal cap before following with the microcatheter.
- 7.
Sometimes crossing epicardial collaterals can prove impossible due to severe tortuosity.
- 1.
Epicardial collateral crossing should always be performed using contrast guidance (i.e., no surfing).
- 2.
Orthogonal injections are important to determine the collateral vessel course.
- 3.
Marked tortuosity and small collateral size reduces the likelihood of successful collateral vessel crossing.
What Can Go Wrong?
- 1.
Ischemia of the myocardium supplied by the collateral, especially if there are no other collaterals supplying the same territory. Ischemia can cause arrhythmias and/or hypotension.
- 2.
Collateral perforation that can cause tamponade. In contrast to prior beliefs, perforation in patients with prior CABG surgery can be more dangerous than perforation in patients with intact pericardium, as it can lead to loculated effusions compressing various cardiac structures (such as the left atrium or the right ventricle ) that cannot be drained with pericardiocentesis ( Section 12.1.1.2.5 ).
- 3.
Collateral dissection (in most cases further attempts to cross can be performed via a different collateral).
- 4.
Guidewire entrapment: To prevent this, the operator should not allow a loop or knuckle to form at the tip of the guidewire during attempts for retrograde crossing of the collateral (see Online Case 13 ), although occasionally tiny loops at the tip of a polymer-jacketed guidewire can help cross tortuous collaterals.
Step 4c Bypass Graft (Online cases 10 , 16 , 29 , 50 , 57 , 61 , 81 , 85 , 87 , 96 , 102 , 103 ).
- 1.
Both arterial grafts and SVGs (either patent or occluded) can be used for retrograde CTO PCI.
- 2.
There is a risk for perforation and distal embolization (with either patent or occluded SVGs).
- 3.
Internal mammary artery (IMA) bypass grafts are the least preferred bypass grafts for retrograde wiring, because insertion of equipment in the graft could result in pseudolesion formation and even antegrade flow cessation, and because injury of the IMA graft might have catastrophic consequences. Moreover crossing collaterals through IMA grafts can cause IMA dissection, especially in tortuous IMA grafts and when rotating the microcatheter through the collateral. The Caravel microcatheter that is designed to cross the collaterals without rotation is preferred in this setting. If the left IMA (LIMA) to LAD is the only available collateral donor, a mechanical circulatory support device should be strongly considered before crossing the collateral (see Online Case 46 ).
- 4.
One of the major challenges of retrograde wiring through bypass grafts is navigating severe angulation at the distal anastomosis (see Online Cases 4 and 47 ). This can be overcome by several techniques, such as using:
- a.
polymer-jacketed guidewires and preshaped microcatheters, such as the SuperCross microcatheters
- b.
the hairpin (also called reversed) guidewire technique ( Section 9.6.2 ), or
- c.
the Venture deflectable tip catheter.
- a.
- 5.
After a native coronary CTO is recanalized, coiling of the SVG may be considered (to minimize risk for subsequent distal embolization and to decrease competitive flow with risk of stent thrombosis), although this approach is controversial.
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