Improvement of Regional Ischemia after Successful Percutaneous<br />
Intervention of Bypassed Native Coronary Chronic Total<br />
Occlusio

During angiography, when the saphenous vein graft (SVG) bypassing a chronic total occlusion (CTO) in a coronary artery is found to be patent without significant obstructive disease, conventional wisdom would suggest adequate distal perfusion supply and negate the need for further intervention. Independent of angiographic appearance, however, SVGs have been shown to exhibit features of endothelial dysfunction.^1,2 Despite the presence of a patent and nonobstructive SVG, regional myocardial perfusion may still be compromised, leading to clinical presentation of ischemia. Recanalization of the native vessel may still be necessary despite a patent SVG.
Controlled antegrade and retrograde subintimal tracking, also known as the CART technique, is a promising approach in percutaneous coronary CTO intervention.^3,4 When a standard antegrade attempt fails to provide successful recanalization, the CTO is simultaneously approached in a retrograde fashion by using accessory channels such as septal and epicardial collaterals, interatrial vessels or bypass grafts.^3–6 With both antegrade and retrograde guidewires in their respective subintimal spaces at the site of the CTO, meticulous balloon inflations and wire manipulations can facilitate the connection of the dissections, leading to successful recanalization.
In this report, 2 patients presented with anginal symptoms and reversible defects on stress nuclear scintigraphy. Corresponding to the regional ischemia, angiography for both patients showed a patent and nonobstructive SVG with normal flow bypassing a native CTO. Percutaneous coronary intervention (PCI) of the patients’ native coronary CTOs, utilizing the patent SVGs as the retrograde access, led to successful immediate procedural results as well as subsequent resolution of symptoms and stress nuclear scintigraphic ischemia.

Methods and Results

The first patient was a 72-year-old-male who was status post coronary bypass surgery (CABG) 9 years prior. He presented with increased exertional anginal symptoms. The patient underwent stress nuclear scintigraphy, which showed a reversible defect in the inferolateral wall. Diagnostic angiography showed patent left main (LM) and left anterior descending (LAD) arteries, without obstructive disease, but a CTO was present in the proximal left circumflex (LCX) and the middle-right coronary (RCA) arteries. Contrast injection of the SVG and the distal bypassed native vessels demonstrated a widely patent sequential graft to the obtuse marginal branch and distal RCA without angiographic obstructive disease and TIMI-3 flow (Figure 1a). Because of the persistence of symptoms, a decision to recanalize the CTO was made. The LCX CTO was chosen over the RCA due to its more favorable angiographic appearance. An antegrade approach, however, was unsuccessful in crossing the CTO, including the use of multiple guidewires: the Prowater^™, MIRACLEBros^™ 3 gram, 6 gram, 12 gram and Confianza^™ Pro 12 gram (Asahi Intecc, Aichi, Japan).
The approach was expanded to include a retrograde approach utilizing the patent SVG as the access conduit. An 8 Fr AL2 guiding catheter was used in the native left coronary system, and an 8 Fr Hockey Stick guiding catheter cannulated the SVG. Due to the additional transit length required in the retrograde approach, the Hockey Stick guide was shortened, as previously described⁷ (see Discussion). While leaving the Confianza^™ Pro antegrade wire in place where it entered the subintimal space at the proximal aspect of the CTO (Figure 1b), the retrograde wire was advanced through the SVG with a RapidTransit^™ (Cordis Corp., Miami Lakes, Florida) microcatheter and probing of the distal end of the CTO was carried out. Use of the microcatheter was essential in protecting the retrograde pathway and enhancing wire maneuverability. Meticulous manipulation of the retrograde wire was necessary to guide lesion penetration over the extended length of the retrograde pathway. The retrograde wire entered into the subintimal space from the distal aspect of the CTO (Figure 1c).
The standard CART technique was continued with a 1.5 x 15 mm Voyager^™ (Guidant Corp., Santa Clara, California) balloon on the retrograde wire advanced to the distal aspect of the CTO where it overrode the distal true lumen and the subintimal space of the CTO. Balloon inflation along this area was performed. After deflation, the balloon was left in place to keep the channel open and to serve as a landmark for the antegrade wire crossing. In this case, however, the antegrade wire failed to find the distal true lumen and a “reverse” CART was performed. Another 1.5 mm balloon was advanced to the proximal aspect of the CTO over the antegrade wire where dilatation was performed in the proximal true lumen and subintimal space of the CTO; in order to create a larger channel, a 2.0 mm and 2.5 mm balloon was also utilized (Figure 1d). After deflation, the balloon was left in place and the distal wire was successful in connecting the distal and proximal dissections into the proximal true lumen (Figure 1e). The proximal and distal true lumens are connected, thereby leading to a successful final outcome (Figure 1f). The CTO was stented with a 2.75 x 33 mm Cypher^™ sirolimus-eluting stent (Cordis) to a final diameter of 3.1 mm. Clinical follow up showed resolution of the patient’s exertional symptoms and the reversible inferolateral defect on the stress nuclear scintigraphy.
The second patient was a 64-year-old-male who was status post CABG 13 years prior who first presented with unstable angina. Diagnostic angiography demonstrated CTOs in all 3 native coronary arteries: proximal LAD, middle LCX and proximal RCA. All of the bypass grafts were occluded except for a sequential SVG to the diagonal branch, which backfilled the LAD and skipped to the distal LCX. The SVG segment between the diagonal branch and the LCX showed a 95% culprit lesion which was successfully treated with a drug-eluting stent without complications. There was no remaining obstructive disease in the SVG, and the flow was TIMI 3.
At follow up, the patient’s symptoms improved but did not completely resolve. A stress nuclear scintigraphy demonstrated a fixed inferolateral defect with peri-infarct ischemia. After discussion with the patient, a decision was made to attempt to recanalize the LCX CTO. The antegrade approach was again attempted first without success; then the retrograde approach was added to the strategy. The native left coronary system was cannulated using an 8 Fr CLS 3.5 guiding catheter, and a shortened 8 Fr AL1 guide was used in the SVG (Figure 2a). As in the first case, the antegrade wire, the Confianza^™ Pro, was left in the subintimal space with its entry site at the proximal cap of the CTO (Figure 2b). With the use of the microcatheter via the SVG access, multiple coronary guidewires were used to probe the distal aspect of the CTO in a retrograde fashion, including the Pilot^™ 150 (Abbott Vascular, Redwood City, California), Prowater^™, MIRACLEBros^™12 gram, Fielder FC and the Confianza^™ Pro (Figure 2c). Once the retrograde wire found an acceptable location in the subintima, balloon dilatation in the distal aspect of the CTO was performed as discussed in the first case (Figure 2d), and the antegrade wire was successful in finding the distal dissection space leading to the distal true lumen (Figure 2e). After deployment of the Cypher stents, final angiography revealed an excellent result (Figure 2f). At follow up, the patient’s angina and nuclear scintigraphic reversible defect had completely resolved.

Discussion
Both patients demonstrated compromised regional myocardial perfusion despite the presence of patent SVGs with normal flow and no obstructive disease. The SVGs were further demonstrated to be viable conduits for retrograde access to the distal aspect of the CTOs in the native coronary artery. Successful procedural outcomes were achieved in both native bypassed CTOs: one utilizing the reverse CART, and other using the standard CART technique. In subsequent follow up, both patients experienced resolution of their anginal symptoms and ischemia by stress nuclear scintigraphy.
Salient points to a successful CART technique may include guide management, use of a microcatheter and low-profile balloons, guidewire technology and technique and knowledge of the anatomy of retrograde channels.^3–5 First, an antegrade approach should be attempted; a retrograde approach should be adjunctive when the antegrade wire cannot locate the distal true lumen, as shown in this study. Aside from choosing the most supportive guiding catheters, appropriate shortening of the retrograde guide is essential in ensuring the target lesion can be reached. By cutting a segment of a vascular sheath (1 French size smaller than the guide), it can be used as a sleeve to conjoin a cut-and-shortened guiding catheter.⁷ Use of the microcatheter is essential to protect retrograde channels, especially important when delicate septal or epicardial collaterals are utilized. The microcatheter can enhance wire manipulations, especially in the retrograde direction where the course of the wire may be long, tortuous and narrow. Standard 1.5 mm low-profile balloon catheters are essential in facilitating tracking to the site of the CTO and in dilating into the subintimal space; 1.25 mm balloons may be an option, but are currently not available in the United States. Understanding the mechanical properties of the various coronary wires, wire maneuverability and the anatomy of retrograde channels for access is vital to the successful application of the CART technique. These latter points deserve separate and expanded reviews, which can be gained with greater operator experience.^3–5 Practice, therefore, can truly make perfect in mastering the CART technique.
In experienced hands, the reported cases demonstrated safety, with no serious complications and high success rates.^3–5 The CART technique, however, has a steep learning curve. Patent SVGs are probably the safest retrograde conduit due to their large size and are less likely to be traumatized compared to the potentially fragile small collateral channels. The SVGs may be a good starting point for interested interventionalists to hone their skills. Mastering this technique will add tremendous options to the overall armamentarium of PCI of CTOs.
Endothelial dysfunction in SVGs, in the absence of significant angiographic lesions, has been implicated in vein graft failure.^1,2 The continuum of SVG degeneration from endothelial dysfunction, angiographic slow-flow, development of an atherosclerotic lesion and eventual occlusion is not well understood. Spontaneous slow-flow in SVGs without an angiographic obstructive lesion, moreover, has been linked to clinical presentation of angina and ischemia, which were reversed after successful PCI of the bypassed native coronary artery.² Adding to this observation, patent and nonobstructive SVGs with normal graft flow can also be associated with compromised distal myocardial perfusion, as demonstrated in this report. The decision to intervene on a bypassed native vessel should perhaps depend on clinical evidence of ischemia, and not solely on the angiographic appearance of the SVG.

References

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