Role of Internal Mammary Artery Bypass Grafts in Retrograde Chronic Total Occlusion Interventions

Abstract: The role of internal mammary artery grafts in facilitating retrograde chronic total occlusion interventions is controversial. We describe two cases demonstrating: (a) retrograde wiring via a left internal mammary artery graft; and (b) using the left internal mammary graft for vessel visualization while retrograde crossing to the right coronary artery was achieved via the native left main coronary artery (triple arterial access). The internal mammary artery grafts can facilitate retrograde chronic total occlusion interventions, but should be used with caution to minimize the risk of injury.

J INVASIVE CARDIOL 2012;24(7):359-362

Key words: internal mammary artery, chronic total occlusion

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The retrograde approach has significantly improved success rates in chronic total occlusion (CTO) percutaneous coronary interventions (PCI).^1,2 Septal or epicardial collaterals are used in most CTO PCI cases, whereas saphenous vein grafts (SVGs) are used in the remaining cases.¹ There is controversy on whether internal mammary artery (IMA) grafts should be used for retrograde CTO PCI, given the risk of graft injury that would compromise perfusion of a large vascular territory. Use of left internal mammary artery (LIMA) grafts has been reported for retrograde intervention of left anterior descending (LAD) artery lesions.³ We herein report 2 cases in which a LIMA to LAD graft was used for retrograde PCI of a right coronary artery (RCA) chronic total occlusion by (a) retrograde wiring of septal collaterals through the LIMA; or (b) visualization of the LAD to enable retrograde wiring of septal collaterals through a left main coronary artery guide catheter.

Case 1

A 68-year-old man with prior coronary artery bypass graft surgery (CABG), and congestive heart failure with prior biventricular implantable cardioverter-defibrillator, presented with medically refractory angina despite optimal medical management. Diagnostic coronary angiography revealed a CTO of the proximal LAD, CTO of the proximal RCA (Figure 1A), and CTO of SVG to the posterior descending artery (PDA; Figure 1B). The right PDA filled by collaterals from the LAD (Figure 1C). A decision was made to proceed with PCI. Previous attempts to recanalize the RCA CTO had failed. A decision was made to attempt PCI of the SVG-PDA CTO.

Bilateral femoral access was obtained with 8 Fr sheaths and anticoagulation was achieved with unfractionated heparin. The SVG-PDA was engaged with a multipurpose guide catheter and contralateral injections were performed via an IMA guide catheter. The CrossBoss catheter (Bridgepoint Medical) over a Pilot 200 guidewire (Abbott Vascular) successfully crossed to the mid-SVG segment, but could not advance any further (Figure 1D). A Corsair catheter (Asahi Intecc Co Ltd) could be advanced to the distal SVG (Figure 1E), but wire entrapment within the catheter occurred, requiring removal of both wire and microcatheter. We were able to successfully cross the right posterolateral branch with a Pilot 200 guidewire (Figure 1F, arrowheads) over a Finecross microcatheter (Terumo) (Figure 1F, arrow). After exchanging the wire for an Asahi soft guidewire, the PLV and entire length of the SVG was predilated restoring antegrade flow (Figure 1G, arrow).

In spite of multiple attempts, we were unable to antegradely wire the right PDA. Because of the large vessel size, we elected to pursue retrograde intervention of the PDA via the LIMA graft. We were successful in wiring the PDA retrogradely via the LIMA graft using a Finecross catheter and a Fielder FC guidewire (Asahi Intecc) (Figure 1H, arrow). The guidewire successfully crossed into the right posterolateral branch, where it was trapped with an antegrade balloon (Figure 1I, arrow) enabling retrograde balloon angioplasty of the PDA (Figure 1I, arrowhead). The PDA was wired antegradely with a Whisper ES guidewire (Abbott Vascular) and further predilation was performed. The posterolateral branch was stented across the bifurcation into the distal RCA; 4 more everolimus-eluting stents were deployed, covering the entire length of the SVG with an excellent final angiographic result (Figure 1J). The patient’s angina subsequently resolved.

Case 2

A 56-year-old man with prior CABG, hypertension, diabetes mellitus, and ischemic stroke presented with recurrent angina despite optimal medical management. His nuclear stress test showed a large reversible inferior perfusion defect. Coronary angiography demonstrated triple-vessel coronary artery disease with a CTO of the mid-RCA (Figure 2A, arrow), patent LIMA-LAD (Figure 2B arrow and Figure 2C), patent Y-SVG to the first and second obtuse marginal branch and occluded SVG to PDA grafts. The right PDA filled by collaterals from the LAD (Figures 2B and 2C). The patient was referred for RCA CTO PCI.

Initially, dual arterial access was obtained with 8 Fr right and left femoral sheaths (Figure 2B). The RCA was engaged using an 8 Fr AL1 and the LIMA with a 6 Fr IM guide catheter. Antegrade crossing attempts using a CrossBoss catheter and a Pilot 200 and Confianza Pro 12 wire (Asahi Intecc) failed due to a poorly defined proximal CTO cap (Figure 2C, arrow).

A third arterial access was obtained through the left radial artery to engage the LIMA to visualize the LAD in order to attempt retrograde approach from the LAD (Figures 2D and 2E). The left main artery was engaged with an XB 3.5 guide catheter and a Fielder FC wire (Asahi Intecc) was advanced via a septal collateral branch to the right PDA. We had difficulty wiring retrogradely via the PDA, as the wire preferentially entered the right posterolateral branch (Figure 2F, arrow).

Repeat antegrade crossing attempts failed (Figure 2G), but we were able to advance the wire retrogradely into the mid-RCA (Figure 2H, arrow). We were unable to re-enter the true lumen retrogradely using a Pilot 200 and a Confianza Pro 12 wire. We used a knuckle wire to advance to the proximal RCA (Figure 2I, arrow). We then performed reverse controlled antegrade and retrograde subintimal tracking (CART) with a 3.0 mm balloon antegradely in the proximal RCA and were able to wire with a Pilot 200 wire retrogradely into the aorta (Figure 2J). We were then able to advance a Pilot 200 wire antegradely to the PDA and intraluminal position was confirmed using intravascular ultrasonography.

After removing the retrograde guidewire and the Corsair catheter, we deployed 3 everolimus-eluting stents in the proximal and mid-RCA restoring TIMI 3 antegrade flow in the PDA (Figure 2K). We could not advance a wire into the right posterolateral branch. The patient had an uneventful recovery and marked angina improvement.

Discussion

The main finding of our study is that IMA grafts can be successfully used for retrograde RCA CTO PCI, either as conduits for retrograde wire crossing (Case 1) or for visualization to enable retrograde wire crossing via a left main guide catheter (Case 2).

Case 1 demonstrates retrograde wire crossing of the RCA via a LIMA graft using septal collaterals. To the best of our knowledge, this is the first such published case. One prior report described use of a LIMA to LAD graft for retrograde crossing of LAD lesions,³ but not for collateral vessel wiring through the LIMA. However, retrograde CTO PCI through the LIMA should only be undertaken as a last resort given the risk of LIMA dissection and catastrophic ischemia. Several precautions should be taken: (1) careful attention to pressure dampening to avoid injury of the LIMA ostium; (2) avoidance of side-hole guide catheters to prevent masking of pressure dampening; (3) shortening of the guide catheter and use of long guidewires (such as the Viper Advance wire that is 335 cm in length - CSI) and long microcatheters (150 cm in length) to allow access to the lesion, especially when retrograde wire externalization needs to be performed; (4) ensuring that the septal collaterals arise distal to the IMA anastomosis, as it may be difficult to wire more proximal collaterals; and (5) avoiding use of tortuous IMAs, as straightening of the vessel using a wire can compromise antegrade flow and cause ischemia.⁴ In cases of tortuous LIMA, use of flexible microcatheters, such as the Finecross (Terumo), Transit and Prowler (Cordis), and soft guidewires is preferred to minimize the risk for pseudolesion formation and decrease or cessation of LIMA antegrade flow.

In case of tortuous IMA grafts, or when the LAD is patent, it may be preferable to perform retrograde RCA CTO PCI by advancing the retrograde wiring through the native left main coronary artery and imaging via the IMA graft, as done in Case 2. Although this requires 3 arterial access sites (2 femoral and 1 radial were used in Case 2), it minimizes the risk of IMA graft injury. In this case, the two functions of a guide catheter, ie, visualization via contrast injection and equipment delivery, are dissociated and each guide catheter performs only one function.⁴

There are additional aspects of our cases that merit discussion. First, although it is always preferable to intervene on native rather than SVG CTOs,^5,6 SVG CTO PCI remains an option when native intervention attempts fail. Conversely, native CTO PCI has been used in cases of acute SVG occlusion that could not be opened.⁷ In other cases, the retrograde approach was successfully used to recanalize SVG^8,9 or IMA¹⁰ CTOs. However, the restenosis rates of successfully recanalized SVG CTOs is high.^11,12 In Case 1, both the native and the SVG supplying the distal RCA were CTOs, but the SVG CTO was attempted only after PCI of the native RCA CTO failed.

Second, several types of microcatheters may be needed during the same CTO PCI case. In Case 1, the CrossBoss catheter was initially used to cross the SVG CTO, allowing rapid progression to the distal SVG.¹³ The CrossBoss catheter has a 1 mm blunt distal tip that can cross the occlusion when the catheter is rotated rapidly using a proximal torque device (“fast spin” technique).^13,14 The CrossBoss catheter may be ideally suited for SVG CTOs that do not have side branches that could be entered by the catheter resulting in perforation. In Case 1, the CrossBoss catheter could not be advanced through the distal part of the occlusion that was crossed using a Corsair microcatheter. The Corsair catheter was designed to facilitate crossing via septal collaterals during retrograde CTO PCI and at the same time dilates the vessel, obviating the need for additional balloon dilation of the septal collateral, which would otherwise be needed to minimize the risk of equipment entrapment and facilitate advancement. However, prolonged dwelling of a guidewire inside the Corsair catheter should be avoided as it can lead to “entrapment,” likely due to clot formation between the guidewire and the catheter lumen wall. Finally, the Finecross microcatheter has the lowest crossing profile of all microcatheters and hence has excellent penetration capacity, while remaining very flexible and hence useful for wiring of tortuous vessels.

Third, although numerous guidewire choices are currently available, many operators favor preferential use of four guidewires for CTO PCI: (1) Fielder XT, which is a polymer-jacketed guidewire with a tapered distal tip and is useful as a first-line guidewire during antegrade crossing; (2) Pilot 200, which is a stiff (4.1 gram tip stiffness) polymer-jacketed guidewire, that is particularly useful when there is ambiguity on the course of the target occluded vessel; (3) Confianza Pro 12, which is a stiff (12 gram tip stiffness), tapered-tip (0.009˝) guidewire with excellent penetrating capacity that is particularly useful when there is good understanding of the course of the target vessel; and (4) Fielder FC, which is a soft, polymer-jacketed guidewire preferred for crossing through collaterals during retrograde CTO PCI. Having such a streamlined approach to guidewire selection for CTO PCI, can facilitate inventory management and training of new CTO operators.

Fourth, the reverse CART is currently the most commonly used technique for retrograde CTO PCI wire crossing, as used in Case 2.¹⁵ In the reverse CART, a balloon is inserted over the antegrade guidewire and inflated, creating a target space for the retrograde guidewire to enter. A large balloon may be needed to facilitate re-entry (a 3.0 mm balloon was used in Case 2). In some cases, intravascular ultrasonography may facilitate the performance of reverse CART.¹⁶

Fifth, retrograde PCI may be required to successfully treat a bifurcation CTO. In Case 1, antegrade crossing into the right posterolateral vessel was achieved via the SVG, but the PDA remained occluded and could not be wired antegradely. Using the retrograde approach via the LIMA and via septal collaterals, the bifurcation was successfully treated. The presence of a bifurcation at the distal cap of a CTO favors a primary retrograde approach.¹⁵

In summary, although IMA grafts can be used during retrograde CTO PCI of the RCA, either for retrograde wiring or for lesion visualization, they should only be used in carefully selected cases to minimize the risk for complications.

Acknowledgment. We gratefully acknowledge the tremendous support of the cardiac catheterization laboratory team at the Dallas VA Medical Center for enabling the development of novel catheterization techniques and the performance of clinical research.

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From the University of Texas Southwestern Medical Center and VA North Texas Healthcare System, Dallas, Texas.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Michael reports support from a Cardiovascular Training Grant from the National Institutes of Health (Award Number T32HL007360). Dr Banerjee reports speaker honoraria from St Jude Medical, Medtronic, and Johnson & Johnson and research support from Boston Scientific and the Medicines Company. Dr Brilakis reports speaker honoraria from St Jude Medical and Terumo; research support from Abbott Vascular and Infraredx; and salary from Medtronic (spouse).
Manuscript submitted September 27, 2011, provisional acceptance given November 14, 2011, final version accepted November 22, 2011.
Address for correspondence: Emmanouil Brilakis, MD, PhD, VA North Texas Healthcare System, Cardiology, 4500 South Lancaster Road, Dallas, TX 75216. Email: esbrilakis@yahoo.com