Saphenous vein grafts (SVGs), despite their inherent inferiority to arterial conduits, still remain the type of grafts most commonly used during coronary artery bypass grafting (CABG).1 The natural and post-interventional biological behaviour of SVGs differ from that of native coronary vessels, increasing the risk of restenosis.2 SVG disease after CABG is a strong predictor of mortality.3 In a recent series, SVG long-term failure rates averaged around 50 % at 10 years.4,5 Repeat procedures are associated with substantially increased morbidity and mortality.3 The outcome of percutaneous coronary intervention (PCI) with bare metal stents (BMSs) in SVG disease is poor compared with PCI in native coronary arteries. The incidence of major adverse cardiac events (MACEs) after 30 days averages around 10 %, while restenosis rates at six months exceed 30 %.6 There are conflicting data for the efficacy of drug-eluting stents (DESs) in SVG PCI, but they have not proved sufficiently efficacious to overcome the limitations of BMSs.7,8
Until 2005, the success rates of operators experienced in conventional PCI techniques for coronary chronic total occlusion (CTO) remained unchanged, averaging 60–70 %,9 and were considerably lower than the success rates in non-occlusive coronary artery disease. As a result, uptake was low, never exceeding 10 % and even decreasing in popularity over time in some areas,10 which meant that, for many years, patients with CTO were primarily managed medically or referred for CABG.
In 2005, the retrograde approach for CTO PCI was introduced,11 and has since been refined,12 substantially increasing the success rates achieved by expert operators to more than 90 %.13 This, along with the further development of antegrade techniques – thanks to dramatically improved CTO-dedicated wires and microcatheters – has led to a revival in enthusiasm for CTO treatment.14,15 These developments have resulted not only in increased success rates, but also in the ability to treat far more complex CTOs than was previously possible. Some of these complex CTOs are observed in post-CABG patients due to their inherent long-standing nature and the suturing of the native vessel to create the distal anastomosis.
In this article, we present the case of a patient with multivessel disease post-CABG, a chronically occluded dominant left circumflex coronary (LCX) artery and a failing SVG graft in that vessel. We address the dilemma of whether to revascularise the degenerating SVG graft, or to recanalise the chronically occluded native vessel.
In December 2010, an 82-year-old man was admitted to our clinic with coronary artery disease and a history of dyslipidaemia, diabetes and smoking. In 1997, he had experienced an anterior wall ST elevation myocardial infarction (STEMI), which had been successfully treated with thrombolysis. That same year, coronary angiography had revealed a dominant left system with 80 % stenosis at the proximal left anterior descending (LAD) artery and 90 % stenosis at the proximal dominant LCX artery. The right coronary artery (RCA) was a small non-deceased vessel. The patient had undergone CABG with implantation of a left internal mammary artery (LIMA) graft in the LAD artery and an SVG graft in the first obtuse marginal branch (OM1).
At the time of presentation to our clinic, echocardiography revealed a normal left ventricular ejection fraction of around 70 % and normal electrocardiogram and laboratory results. Coronary angiography revealed 80 % proximal stenosis in the LAD artery and an occluded and/or underdeveloped LIMA. The small RCA was normal. The LCX artery was totally occluded proximally and there was 90 % ostial stenosis of the SVG OM1 and 80 % sequential mid-body stenosis. We also found 90 % ostial stenosis proximal to the anastomosis at the native marginal branch that provided flow to the dominant distal LCX artery (see Figure 1).
It was decided to treat the native vessels. The decision was based on the focal nature of the stenosis in the proximal LAD artery, the short length (<20 mm) of the CTO in the LCX artery, the very extensive disease in the SVG, and the presence of severe atherosclerosis proximal to the anastomosis, which would have led to incomplete revascularisation with sole SVG treatment.
After bifemoral artery access, a 6 French (Fr) EBU4 catheter (Launcher®, Medtronic) was placed in the left main coronary artery and a 7 Fr JR4 catheter (Launcher) was placed at the ostium of the SVG. Bilateral contrast injection revealed the anatomical details described above (see Figure 1E).
The LAD artery was treated first (see Figure 2). After crossing the lesion with a Fielder FC® wire (Asahi Intecc) and pre-dilatation with a 2.5x20 mm balloon (Invader®, Alvimedica Medical Technologies), a 3.0x28 mm rapamycin-eluting stent (CORACTO®, Alvimedica Medical Technologies) was implanted in the proximal LAD artery, covering the ostium of a sizeable first diagonal branch (D1). Angiography following kissing balloon post-dilatation with a 2.0x15 mm Invader non-compliant (NC) balloon in the D1 and a 3.5x20 mm Invader NC balloon in the LAD artery revealed thrombolysis in myocardial infarction grade 3 (TIMI 3) flow and no residual stenosis.
The LCX artery occlusion (see Figure 3) was initially attempted with a Fielder FC wire supported by a 130 cm Finecross® microcatheter (Terumo Interventional Systems); however, this wire failed to penetrate the proximal cap. Consequently, a Fielder XT® wire (Asahi Intecc), a Miracle 3® wire (Asahi Intecc), a Pilot 150® wire (Abott Vascular) and a Confianza Pro 12® wire (Asahi Intecc) were used in an antegrade approach, employing the parallel wire technique. This also failed to reach distal true lumen, either at the OM1 or at the distal LCX artery. A retrograde approach via the SVG was then attempted. After pre-dilatation of the tight ostial stenosis of the SVG with a 2.0x30 mm Invader balloon to avoid any ischaemic phenomena, a 150 cm long Corsair® microcatheter (Asahi Intec) was advanced to the distal cap over a Fielder FC wire. After failure to penetrate the distal cap with Fielder FC and Miracle 3 wires, a Confianza Pro 12 wire subintimally crossed the occlusion, entering a proximal atrial branch. This meant that advancement to the proximal LCX artery was not possible. The Corsair microcatheter was removed using the trapping technique by wire entrapment in the guiding catheter with inflation of a 2.5x15 mm Invader balloon. Subsequently, the occlusion was dilated in a retrograde approach using Invader 2.5x15 mm and Invader 3.0x15 mm balloons – i.e., the so-called control antegrade retrograde subintimal tracking (CART) technique. During inflation, a very deep engagement of the JR4 was achieved, almost reaching the distal anastomosis.
Despite the use of retrograde dilatation and CART technique, antegrade wire crossing was also unsuccessful, hence retrograde stenting was performed with CTO coverage with a 3.0x17 mm CORACTO rapamycin-eluting stent, which covered the OM1–LCX artery bifurcation (see Figure 3D). After stabilisation of the subintimal space with the stent, access to the distal true LCX artery was easily achieved through the struts of the stent using a Pilot 150 wire.
Following stent fenestration and sequential pre-dilatation with an Invader CTO 1.25x10 mm balloon and an Invader 3.0x15 mm balloon, a 3.0x28 mm CORACTO rapamycin-eluting stent was implanted in the direction proximal to the distal LCX artery, covering the ostium of the OM1, thereby constituting a culotte stenting bifurcation technique, with the stent previously implanted via the retrograde route.
Afterwards, kissing balloon post-dilatation was performed over the bifurcation, with the use of two Invader NC 3.0x15 mm balloons in the LCX artery and OM1 (see Figure 4). A more distal stenosis in the OM1 was treated with a CORACTO 3.0x13 mm rapamycin-eluting stent. Final angiograpy revealed TIMI 3 flow in both branches with retrograde filling of the SVG graft and no residual stenosis. Angiographic follow-up at six months revealed no signs of in-stent restenosis in either the LAD or the LCX arteries (see Figure 5). The patient remained completely asymptomatic.
The CORACTO stent was developed in 2002 and is a stainless steel stent with a strut thickness of 88 μm and a 4 μm coating allowing controlled release of 1.7 μg/mm2 of rapamycin. The coating is made from a polylactic-co-glycolic acid-based biocompatible copolymer, which biodegrades to lactic acid and glycolic acid. After complete drug release and degradation of the polymer, the BMS remains in the vessel. Preclinical animal testing has revealed minimal vessel inflammatory reaction, similar effectiveness in reducing neointimal formation and greater endothelial recovery when comparing the CORACTO stent with other DESs.16 A clinical study in 46 patients with CTO lesions revealed a late lumen loss (LLL) of 0.77 mm±0.63 mm at six months. No deaths, myocardial infarctions (MIs) or stent thrombosis had occurred at six months follow-up. At 24 months, the overall target vessel revascularisation (TVR) rate was 10.8 %, with no reported stent fracture.17
When compared with the first generation of sirolimus-eluting stents (for example, Cypher®, Cordis Corporation), which had a strut thickness of 140 μm and a non-absorbable 12 μm polymer coating, the CORACTO stent seems to have favourable mechanical characteristics. In the ACROSS-Cypher total occlusion study of coronary arteries 4 trial (TOSCA trial), which used the Cypher stent, median LLL was 0.10 mm (-0.57, 0.15) and the MACE rate was 10.3 % at one year.18 Moreover, a very high rate of stent fracture (16 %) was observed.
Coronary artery bypass surgery is a mainstay of treatment for coronary artery disease. SVGs are the most common types of grafts used in CABG, even though they have a progressive closure rate estimated to be 12–20 % at the end of the first year, and a long-term failure rate of almost 50 % at 10 years.1,4,5 SVGs fail, despite optimal medical therapy, because of their unique, inherent biological behaviour post-CABG. Lesions in SVGs generally sustain a higher plaque burden, more friable material and frequent superimposed thrombosis related to the higher risk of distal embolisation and peri-procedural myocardial damage.19,20
Currently, SVG interventions account for 5–10 % of all PCIs performed annually in the US.21,22 Treatment of SVG stenosis with PCI is associated with a 15–20 % incidence of MACE within 30 days,3 mainly peri-procedural MIs due to distal embolisation of atherosclerotic plaque and friable debris, causing microvascular occlusion and no reflow,6,23–26 which is predictive of late mortality in this patient population2 and confers a poor long-term clinical outcome.27–28
BMSs implanted in SVGs produced outcomes certainly inferior to those of BMSs implanted in native coronary arteries, with a 30-day MACE rate of around 10 % and a six-month restenosis rate exceeding 30 %.17 Despite the optimism regarding their effectiveness in native coronary arteries, DESs have produced conflicting results in several observational studies and small randomised trials.7,8,29,30
Coronary CTOs still represent one of the most common reasons for referral for bypass surgery; many other patients are left untreated due to technical and procedural complexities.28 The benefits of successful CTO recanalisation are related to improved survival,9,31 improvement in anginal status32 and left ventricular function,7 decreased need for CABG, and increased exercise tolerance.33,34 Most notably, the presence of a large ischaemic burden (more than 10 %) is an important determinant of the revascularisation benefit in patients with symptomatic CTO.35 CTO PCI is technically challenging and associated with certain complications, but is traditionally considered a low-risk procedure, with an average MACE rate of 4–5 % if performed by an expert practitioner.
Technical and procedural success rates for CTO PCI have steadily risen over the last five years, as a result of increased operator experience, improved materials, the refinement of the antegrade approach and the introduction of the retrograde approach, alongside the development of dedicated groups of experts focusing on technical development, training and education worldwide.14 In a recent contemporary series of retrograde procedures, experienced operators achieved success rates of 90–95 %.36
When it was initially developed, the retrograde approach was mainly used as a second-line therapy after failure of the antegrade approach in repeat procedures. Shifting to the retrograde route after extensive antegrade failure at the same procedure was shown to have inferior outcomes.14 With the evolution of the techniques and increased operator experience, recent trends support the implementation of the retrograde technique during the same procedure, but after a short, focused antegrade failure.37 This is the strategy that we followed.
The main challenge with the retrograde approach is the connection between the antegrade and retrograde subintimal spaces. Many techniques have been used, including CART (with subintimal space creation via retrograde balloon dilatation), reverse CART (with subintimal space creation via antegrade balloon dilatation)12 and stent–reverse CART (with stabilisation of the subintimal space via stent implantation). These techniques may or may not be facilitated by the use of intravascular ultrasound.
In this article, we have described for the first time the stabilisation of the subintimal space with retrograde stent implantation (stent–CART technique). This technique is easily achieved via SVG conduits and could potentially also be applied with retrograde stenting via septal collateral conduits.38 For safety and efficacy reasons, the decision in this case was to open the native LCX artery. Such a decision cannot be generalised; it should be based on clinical and anatomical criteria, such as the complexity of the CTO or SVG anatomy. In other cases, treatment of the SVG might be considered a better option.
The rate of SVG failure after CABG currently reaches 50 % at 10 years. Repeat procedures carry substantial risk, and long-term outcomes with SVG PCI are still poor, with success rates significantly inferior to those seen with PCI in native coronary arteries. Owing to increasing operator experience and the development of more sophisticated techniques, CTO PCI is currently achieving high procedural success rates and could be an alternative and efficient approach for treating chronically occluded coronary arteries bypassed by failing SVGs.