SVG to Circumflex Stenting with Significant Distal and Proximal Disease: A Complex Case Utilizing a Covered Stent

 A 70-year-old white male presented with a history of progressive, unstable angina and dyspnea on exertion. He had a history of coronary artery disease, status post coronary artery bypass graft surgery (CABG) in 1990 with a redo CABG in 2000. In 1990, he had a LIMA to LAD (left internal mammary artery to the left anterior descending coronary artery), SVG to PDA (saphenous vein graft to posterior descending artery), and SVG to OM (obtuse marginal artery)

In 2000, his LIMA to LAD was occluded, probably because LIMA graft was atretic and failed to thrive, and the SVG to PDA was also occluded. At that time, he had a repeat CABG with an SVG to LAD and SVG to PDA. He also had a history of hypertension, hyperlipidemia, and ventricular tachycardia that required an automated implantable cardioverter-defibrillator. Nuclear stress testing revealed a reversible defect in the inferior wall and because of his clinical presentation, non-invasive test results, and extensive history of coronary artery disease, a cardiac catheterization was performed to assess his coronary arteries and bypass grafts. 

Cardiac catheterization demonstrated occluded native left and right coronary arteries, and a LIMA to LAD graft that was known to be occluded past the distal anastomosis. There were also two patent SVGs supplying circulation to the heart. There was a widely patent SVG to the LAD that also supplied collateral circulation to the right coronary artery. An SVG to the circumflex supplied the circumflex territory and also provided collateral circulation to the right coronary artery (RCA). This graft had several significant lesions, including severe, diffuse disease in the proximal graft, just distal to the aortic anastomosis. There was also a severe, diffuse, thrombotic lesion approximately 20 mm proximal to the distal anastomosis (Figure 1).

Due to the location and severity of the disease in the SVG to the circumflex artery, the procedure was stopped, and a multi-disciplinary strategy was coordinated to revascularize the patient. Cardiothoracic surgery was consulted to review the case for potential bypass surgery to the LAD, RCA, and circumflex arteries. Post-catheterization, the patient was medically managed and discharged on medications including aspirin, clopidogrel and statins, while the physicians determined the best approach for treating the SVG to OM graft.

Clinical management

Following surgical consultation, the patient was recommended for percutaneous coronary intervention (PCI) of the SVG to circumflex because of the history of CABG x 2, a widely patent SVG to LAD graft providing circulation to the anterior and inferior wall, and previous use of the LIMA graft site. Because of the inability to protect the distal lesion with a distal protection device, and the absence of proximal protection devices on the market, it was decided that a covered stent in the distal lesion would minimize the potential for a major embolic shower and potential myocardial infarction. A drug-eluting stent (DES) with distal protection would then be used to stent the proximal stenosis. 

SVG PCI is associated with a high risk of major adverse cardiac events (MACE), mainly peri-procedural MI, resulting predominantly from distal embolization of atherosclerotic plaque and friable debris within the graft, causing microvascular occlusion and no reflow.¹ Studies show that use of a distal embolization protection device minimizes MACE and no-flow peri-procedure, and is standard of care. Additionally, clinical experience with various embolic protection devices (EPDs) has shown that the capture and retrieval of potentially embolic debris reduce adverse events in situations where the amount of debris is largest, such as saphenous vein grafts and where the end organ is most sensitive (myocardium, with no reflow and creatine kinase (CK)-MB release.² However, in this specific case, the SVG lesion was too distal to allow a protection device and there are no proximal protection devices currently on the market. Therefore, because of the high risk of embolic showering from the large burden of debris in the distal lesion, special permission was requested from the Institutional Review Board to approve the use of a covered stent in the distal saphenous vein lesion to minimize the potential for a major embolic shower. The Institutional Review Board has only approved covered stents in coronary intervention for vessel perforations, and the patient had to be fast tracked through a review process to get authorization to place a covered stent in the distal lesion. After obtaining approval, the patient was scheduled for a complex PCI of the SVG to circumflex artery using a covered Jostent (Abbott Vascular)³ in the distal lesion, and a DES with distal protection for the proximal lesion.

Procedure

The right common femoral artery was accessed with an 8 French (Fr) sheath, and the left common femoral artery was accessed with a 4 Fr sheath, in case an intra-aortic balloon pump (IABP) was needed. After gaining access, the patient was anti-coagulated with bivalirudin and a therapeutic activated clotting time (ACT) of 389 was achieved. The SVG to the circumflex artery was engaged with an 8 Fr HS1 guide catheter (Medtronic) and a 190 cm Runthrough wire (Terumo) was advanced past the distal anastomosis into the native circumflex artery. Before deploying the covered Jostent, a 20 mm angioplasty balloon was placed distal to the lesion to ensure that the patient was not a candidate for a distal protection device. There was an inadequate landing zone for the distal protection device (Figure 2), and therefore the distal lesion was stented using a covered stent, a 5.0 x 26 Jostent. To provide additional protection, intracoronary nicardipine was administered to prevent no-reflow phenomenon. Nicardipine was chosen because it is considered to be the most potent calcium-channel blocker to prevent no-reflow while also having the fewest systemic side effects.⁴ 

After successful stenting of the distal lesion (Figure 3), a distal protection device was deployed to protect the proximal vessel from potential embolic showering (Figure 4). The proximal vessel was then stented with a 4.0 x 33 mm Xience Prime stent (Abbott Vascular), an excellent angiographic result was achieved (Figure 5), and the procedure was completed without complication. A Starclose device (Abbott Vascular) was used to gain hemostasis of the right femoral artery. Left femoral artery hemostasis was manually achieved. The patient was routinely discharged the following day, without complication.

Outcome

Three months post stenting, the patient is asymptomatic, and is followed on a regular basis by the attending interventional cardiologist. As part of his medical therapy, he is being treated more aggressively for hypertension and hyperlipidemia, and is on a dual anti-platelet regimen of aspirin and clopidogrel. Hyperlipidemia is considered a major risk factor for SVG disease and in-stent stenosis, so more aggressive lipid control therapy was used to reduce the progression of atherosclerosis.⁵

Discussion

The location of the SVG disease, as well as the large thrombotic burden in the distal graft, created a unique and complicated situation for PCI. While distal protection is the standard of care, the distal SVG lesion did not allow room for this strategy. Proximal protection devices have been used, but currently there are none on the market. Therefore, a multi-disciplinary team decided that a covered stent would prevent distal embolization and serve as the most effective protection strategy.  While randomized trials have shown no advantage for covered over bare metal stents, this case was an exception that required permission from the Institutional Review Board.⁶

Institutional Review Boards are designed to protect patients from inappropriate research or use of investigational drugs. They are known as independent ethics committees or ethical review boards. They are FDA-approved committees that are formally designated to approve, monitor, and review biomedical and behavioral research involving humans. They often conduct a risk-benefit analysis in an attempt to determine whether or not research should be done, and they are designed to protect patients from harm and inappropriate procedures.⁷ The Institutional Review Board at the University of Pennsylvania requires a quorum of at least 5 members that includes scientific and non-scientific personnel, and at least one member who is unaffiliated with the entity.⁸ This diverse body is designed to promote objectivity and reduce bias in any decisions that are made.

For this procedure, the University of Pennsylvania’s Institutional Review Board approved the Jostent for a special exemption for a single patient, known as the Humanitarian Device Exemption provision (HDE). This provision is granted less than 4000 times per year in the United States and is used when no comparable device is available, there is not significant risk of injury to the patient, and the potential benefit of the device outweighs the risk of its use.⁹ This does not mean that the FDA is endorsing the product for this specific use, but that an ethical and rigorous review process was conducted before performing the procedure. 

For a procedure requiring Institutional Review Board approval, the patient must agree to the procedure and sign consent, and the hospital’s medical staff should also endorse the use of the product with supporting letters to the board. In an emergency, the Institutional Review Board can be notified after the use of this type of product, but it is advisable to follow protocol and gain approval to minimize potential abuse of off-label products. 

After the case, a follow-up report needs to be forwarded to the Institutional Review Board to discuss the device usage and the patient outcome. This documentation provides the board with essential information regarding its decisions. It protects patient safety, enhances oversight of off-label product usage, and safeguards ethics in medical practice. In this case, a report was sent to the board to inform them of the technical and clinical results of the procedure.

This case was also unique because numerous randomized trials have been conducted to determine the efficacy of covered stents to treat disease in saphenous vein grafts. These trials include STING¹⁰, BARRICADE¹¹, PROTECT¹², and SYMBIOT¹³, all of which show no advantage to using covered stents in saphenous vein grafts. In general, the prognosis for SVG stenting is poor, with restenosis rates of  > 20% after three years, and with DES being superior to bare metal stents for short- and long-term patency and MACE rates.¹⁴ SVG occlusion during the first year post-CABG is high at 15%, and 10-year patency is only 60%. SVG failure is also associated with a significant increase in MACE, including death, MI, and the need for repeat revascularization.¹⁵

While covered stents are not approved or indicated for native coronary arteries or bypass graft intervention, except in the case of vessel perforation, the severity of this lesion, along with the inability to protect the distal vessel from embolic shower, made this case uniquely suited for a covered stent. This patient already had two CABGs and, after surgical consultation, was not considered a candidate for a third CABG. The lack of a viable proximal protection device on the market was also a major factor in gaining Institutional Review Board approval for the covered stent in the distal lesion. It is important to note that in the major clinical trials on covered stent grafts, ability to protect a distal lesion with the type of thrombotic burden seen in this case was not considered. These trials were randomized trials comparing open stents versus covered stents. Therefore, in difficult cases like this, it is important to keep all options available in order to keep the graft patent, while minimizing procedural complication rates because of embolic showering.

Also, because of the risk of emboli and high restenosis rates for PCI, SVG angiography and interventions should be undertaken with knowledge of operative reports and any prior angiograms. It is important to know the number, location, and anatomy of grafts. This reduces contrast load, radiation exposure, and vascular complications that may occur when performing high-risk catheterizations and interventions. In this case, the baseline knowledge and well-developed interventional strategy also reduced procedural time, which can further minimize complications. Most importantly, a well-planned procedure allows the cardiac cath lab staff and surgical support team to be fully prepared for all contingencies that may arise during such complex procedures.

Conclusion

This case posed significant technical challenges because of diffuse disease in the proximal and distal graft, and the strategy to use a covered stent was considered the best option for this patient’s distal lesion. While literature supported the use of a DES with a distal protection device for the proximal lesion, there are no current guidelines for the management of distal SVG lesions without room for distal protection. SVGs are vulnerable to no-reflow phenomenon and embolic showers without protection, and because of the excessive thrombotic debris present on angiography in the distal lesion, the use of a covered stent strategy to protect against embolization was determined to be the best treatment option for this patient. It is important to note the importance a multi-disciplinary approach in planning SVG interventions, and that surgical support may be necessary. In cases like this, treatment options are limited and need to be tailored to the individual patient. The time and effort spent to coordinate and plan this particular, complex interventional strategy resulted in technical and clinical success.

This article received double-blind peer review from members of the Cath Lab Digest editorial board.

Disclosures: The authors report no conflicts of interest regarding the content herein.

The authors can be contacted via Richard J. Merschen, EdS, RT(R)(CV), RCIS, at richardmerschen@verizon.net.

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