|MISCELLANEOUS - MY APPROACH
|Year : 2015 | Volume
| Issue : 3 | Page : 281-284
My approach to a SVG graft with total occlusion: Illustrated with a case
Sunil K Verma1, S Ramakrishnan1, Ruma Ray2, B Bhargava1
1 Department of Cardiology, All India Institute of Medical Sciences, New Delhi, India
2 Department of Pathology, All India Institute of Medical Sciences, New Delhi, India
|Date of Web Publication||23-Feb-2016|
Sunil K Verma
Department of Cardiology, All India Institute of Medical Sciences, New Delhi
Source of Support: None, Conflict of Interest: None
Management of a patient with acute coronary syndrome after coronary artery bypass grafting (CABG) is challenging. Increasing age, associated co-morbidities, and progressive deterioration in left ventricular function make the scenario even worse. The escalation of ongoing medical treatment is usually the first step. Re-CABG is often not an option. Then, this becomes a compelling situation for an interventional cardiologist to perform an intervention to relieve the symptoms and sometimes repeated interventions. Conventionally, two types of interventions are described in this situation, either the intervention on native coronaries or intervention on graft vessels. Percutaneous revascularization is associated with higher rates of in-stent restenosis, target vessel revascularization, myocardial infarction, and death compared with native coronary arteries. Use of embolic protection devices is a Class I indication to decrease the risk of distal embolization. Nonetheless, these devices are underused. Most evidence supports treatment with drug-eluting stents. We illustrate the management with a case. This case used a thrombus aspiration device prior to stent deployment in saphenous vein graft to get optimal results without any "slow-flow" or "no-flow."
Keywords: Acute coronary syndrome, coronary artery bypass grafting, percutaneous coronary intervention, saphenous vein graft
|How to cite this article:|
Verma SK, Ramakrishnan S, Ray R, Bhargava B. My approach to a SVG graft with total occlusion: Illustrated with a case. J Pract Cardiovasc Sci 2015;1:281-4
|How to cite this URL:|
Verma SK, Ramakrishnan S, Ray R, Bhargava B. My approach to a SVG graft with total occlusion: Illustrated with a case. J Pract Cardiovasc Sci [serial online] 2015 [cited 2019 Jul 20];1:281-4. Available from: http://www.j-pcs.org/text.asp?2015/1/3/281/177293
Recurrent ischemia leading to unstable ischemic syndromes is common after more than 3 years of surgery.  In 70-80% of postcoronary artery bypass grafting (CABG) patients presenting with acute coronary syndrome, the culprit lesion is located in a saphenous vein graft (SVG). , Atherosclerotic plaques in the vein grafts are morphologically different than those in native coronary arteries. They contain foam cells, cholesterol crystals, blood elements, and necrotic debris, with less fibro collagenous tissue and calcification than present in native coronary arteries. ,, Consequently, the plaque in older vein grafts may be softer, more friable, as well as being larger than those observed in native coronary arteries, and they frequently have associated thrombus formation. The vein graft pathology is therefore different, lacking the fibrous cap and compensatory positive remodeling and the potential for increased distal emboli.
Although a wide variety of modifications have been used in percutaneous coronary intervention (PCI) of chronically occluded grafts, none has shown satisfactory results in this challenging intervention subset. ,,,,, The risk of distal embolization is especially high, with "no-reflow" phenomenon being reported in up to 31.8% after PCI of SVGs  and high restenosis rate.  Interventions in SVGs are associated with higher rates of in-stent restenosis, target vessel revascularization, and mortality as compared to native vessel intervention. Evidence supports the use of drug-eluting stents (DESs) in these patients, but covered stents have not been found to be beneficial. The use of embolic protection devices is a Class I indication as per various guidelines, though the use is less in clinical practice. Various pharmacological interventions have been shown to reduce the problems of no-reflow.
The decision to intervene is usually in the setting of an acute infarction, refractory angina, or for grafts covering major territory where native arteries cannot be tackled.
Hence, once the treatment plan of graft intervention is decided, following are the modalities that are used to optimize the results of SVG graft intervention either alone or in combination.
The strategy of intervention is based on understanding the kind of block that is there in the SVG. Studies have shown friable, degenerated atheromatous, and thrombotic debris in the grafts. This is similar to the fibrinous material we extracted with the thrombustor in the case we describe later. Because of this kind of material, it is always preferred to intervene in the native vessel, if possible.
Adverse events due to the procedure, including rise in cardiac enzymes, are predicted by lesion length, greater angiographic degeneration, higher plaque volume, female sex, and chronic renal insufficiency. The use of embolic protection devices has been shown to reduce periprocedure myocardial infarction rates.
In patients with occluded SVGs,  the rates of reconciliation are relatively lower (68). In this study, at 18 months, in-stent restenosis and target vessel revascularization was 68% and 61%, respectively, even with the use of DESs in 95%. This again supports attempts to recanalize the native vessels.
| Pharmacological Support|| |
The role of glycoprotein IIb/IIIa antagonists in SVG intervention is limited, as they have not shown a reduction in periprocedural myocardial infarction in SVG interventions. Bivalirudin in small studies has shown an advantage in reducing ischemic events, but there are no large randomized studies available.
No re-flow can be tackled by adenosine. High doses of intragraft adenosine (≥5 boluses of 24 μg each) have been found to lead to a reversal of slow or no-reflow. Intracoronary administration of nitroprusside (dose: 200 μg) can result in significant and rapid improvement in flow, but can cause significant hypotension in patients who are volume depleted or hypotensive at baseline. Prophylactic use of intragraft verapamil (100-500 μg) and nicardipine have been shown to reduce no re-flow.
| Choice of Stents|| |
The reduction of restenosis in saphenous vein grafts with cypher sirolimus-eluting stent trial reported that sirolimus-eluting stents reduced late loss, target lesion, and vessel revascularization compared with bare-metal stent (BMS) at 6-month follow-up.  Many meta-analyses comparing DES with BMS in SVG intervention have reported lower mortality, major adverse cardiac event (MACE), target lesion revascularization, and target vessel revascularization.  Stents covered with a mesh, most commonly polytetrafluorethylene, have a theoretical advantage over conventional stents because they may "trap" friable atheroemboli and prevent distal embolization. However, 3 prospective randomized trials failed to demonstrate a benefit with covered stents. Symbiot III compared the self-expandable PTFE-covered nitinol Symbiot stent with BMS. At 8 months, the incidence of MACE between the Symbiot group and BMS was similar. Two recent covered stents have shown promise, although comparison data with BMS are lacking. Preliminary results with the MGuard stent, a BMS with a polymeric net attached to its surface, demonstrated favorable early results in a study that included 16 patients who underwent SVG intervention. As of now, the strength of data supports the use of DES, the rest is experimental. ,
| Technique|| |
It has the potential benefit of trapping debris and decreasing distal embolization that may occur from repeated balloon inflations, and in a registry, direct stenting was associated with nearly 50% reduction in CK-MB elevations.
It is common in SVG interventions (90%). There is Class I guideline recommendation for the use of embolic protection devices in SVG intervention, but overall adoption remains low and embolic protection was only used in 23% of patients in registry data. Devices include occlusion balloon plus aspiration systems, distal filter-based devices, and proximal flow interruption catheters.
Other techniques used have involved the use of intracoronary thrombolysis to reduce the thrombus burden, directional coronary atherectomy, laser angioplasty, ultrasound thrombolysis, angiojet rapid thrombectomy, and three-staged protocol using undersized balloon, followed by anticoagulation therapy followed by the treatment according to angiographic result including (9) use of stents (BMS/DES/Membrane covered stent).
Use of export aspiration catheter (EAC) has been shown to reduce the thrombus burden in the SVG graft prior to stent placement.  A medtronic EAC (Medtronic, Inc., Minneapolis, Minnesota) has also been used successfully in the cases of primary PCI of SVG graft. 
In the case discussed below, the use of a simple thrombus aspiration device alone prior to stent deployment provided us optimal results without any "slow-flow" or "no-flow." However, more data are needed to confirm the efficacy of this modality of treatment in this group of patients.
| Case|| |
A 76-year-old lady presented to us with Class IV angina of recent onset (1-month duration). She underwent CABG 8 years back with 4 SVG grafts to the left anterior descending, diagonal, obtuse marginal (OM), and posterior descending arteries for triple vessel disease (TVD). She is hypertensive and nondiabetic. There is also aliment of renal dysfunction (blood urea 62 mg % and serum creatinine 2.4 mg %). She was hospitalized and was started on maximal anti-anginal treatment along with heparin, but her angina failed to be controlled. Then, she was taken up for coronary angiogram with all precautions. Her angiogram revealed native TVD.
All the SVG grafts were occluded from the origin (except for the one given to one of the OM). This graft to OM was also having a total occlusion after the origin [Figure 1]. Furthermore, this graft to OM was the only vessel that could be considered for intervention as the clinical scenario was pointing toward a recent thrombotic occlusion responsible for recent clinical worsening. Another option was re-do CABG, but the option of surgery was deferred by surgeons considering the age and co-morbidities.
|Figure 1: Coronary angiogram showing total occlusion of graft to obtuse marginal just after the origin.|
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Hence, PCI of this SVG graft was planned a week later to minimize contrast-induced renal dysfunction. The lesion was crossed with a soft tip wire and initially was dilated with a noncompliant balloon. Angiogram after balloon dilation revealed a lot of atherothrombotic burdens.
Then, a thrombus aspiration device was passed across the lesion multiple times, and a considerable reduction in thrombus burden was achieved.
The aspirated material [Figure 2]a was sent for histopathological examination, which revealed fibrinous material [Figure 2]b. Thereafter, SVG graft was stented serially with 3 DESs with good end result [Figure 3].
|Figure 2: (a) ×20 H and E stain. Fibrin and macrophages are making 50-55% of field. (b) ×100 immunohistochemistry stain, CD68 showing stained macrophages (brown colored), foam cells, and cholesterol cleft.|
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The approach to a SVG graft is summarized in [Figure 4].
|Figure 4: Approach to saphenous vein graft intervention. CABG: Coronary artery bypass surgery, CAG: Coronary angiogram, CSA: Chronic stable angina, ECG: Electrocardiogram, GDOMT: Guideline directed optimal medical therapy, In: Intervention, NSTEMI: Non ST elevation myocardial infarction, PCI: Percutaneous coronary intervention, STEMI: ST elevation myocardial infarction, SVG: Saphenous vein graft, Sx: Surgery, UA: Unstable angina.|
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| Conclusion|| |
Vein graft intervention is a high-risk procedure, as there is a frequent association of bulky thrombus burden with the lesion. The alternate of a redo-CABG is not often available, and therefore, PCI is often the only option. Therefore, knowledge of the techniques of maximizing the benefits will go a long way to improving the results in this sub group of patients.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 2], [Figure 4]