A Percutaneous Intervention Strategy for Chronic Total Occlusions of Saphenous Vein Grafts with Absence of Native Artery Revascularization Options

Abstract

Percutaneous revascularization of chronic total occlusions of saphenous bypass grafts have a relatively low success rate and considerably higher adverse event rates, leading to a non-recommendation based on current guidelines. However, due to absence of native artery revascularization options, occasional intervention of occluded vein grafts is necessitated. Herein, we describe a successful revascularization of a chronically occluded saphenous bypass graft using an intra-graft perfusion balloon and laser atherectomy for debulking prior to stenting with distal embolization protection.

Case Presentation

A 75-year-old female with history of coronary artery bypass graft (CABG) surgery [LIMA–>LAD, sequential SVG–>OM1–>OM2, SVG–>RCA*] and subsequent percutaneous interventions to the bypass grafts [PCI of sequential SVG–>OM1–>OM2 and SVG–>RCA], diabetes, hypertension, and dyslipidemia presented with decompensated heart failure hallmarked by progressive shortness of breath, dyspnea on exertion, and lower extremity edema. Laboratory analysis on admission revealed negative cardiac biomarkers for myocardial infarction with an elevated B-natriuretic peptide [1700+]. Echocardiogram identified diminished left ventricular ejection fraction (EF) of 30-40%, moderate to severe hypokinesis of the anterolateral and inferolateral walls, and severe mitral regurgitation. Subsequent coronary and graft angiography identified occluded native coronary arteries with patent LIMA–>LAD graft supplying an atretic native LAD (Figure 1), patent SVG–>RCA graft with faint collaterals to distal left circumflex (Figure 2), and proximal occlusion of sequential SVG–>OM1–>OM2 (Figure 3). Since the sequential SVG–>OM1–>OM2 graft was the only option available for revascularization and was known to be patent 7 months prior, a decision was made to perform high-risk PCI of this graft.

An intra-aortic balloon pump was placed to provide hemodynamic support during the high-risk PCI. An AR1 guide (Medtronic, Minneapolis, Minn.) was used to engage the SVG–>OM1–>OM2 graft. A Miracle Brothers 12 gm (Asahi, Japan) wire was advanced across the occluded segment into the distal vein graft and serial dilations performed using a Sprinter 1.25 x 8 mm balloon (Medtronic) at 16 atmospheres (atm) (Figure 4). A ClearWay 1.5 x 20 mm perfusion balloon (Atrium Medical, Hudson, New Hampshire) was used to deliver a single intra-graft bolus of eptifibatide within the occluded segment, followed by laser atherectomy using a 0.9 mm excimer laser coronary atherectomy (ELCA) catheter (Spectranetics, Colorado Springs, Co.), with multiple runs at 50/50 and 80/80 settings (Figure 5). A Spider 4.0 mm filter (ev3, Plymouth, Minn.) was then delivered for distal embolization protection at the proximal edge of the sequential limb of the graft (Figure 6). Aggressive balloon angioplasty with an NC Quantum Apex 3.5 x 15 mm balloon (Boston Scientific, Natick, Mass.) was followed by stenting using overlapping Integrity (Medtronic) 3.0 x 30 mm, 3.5 x 30 mm, 4.0 x 30 mm, and 4.5 x 15 mm stents (distal to proximal) at 10 atm. Post-dilatation using an NC Quantum Apex 4.0 x 20 mm balloon at 18 atm yielded good angiographic result and TIMI-3 flow (Figure 7). However, a subsequent angiogram following retrieval of the filter showed TIMI-2 flow through the graft with occlusion of the OM1 branch (Figure 8). A PT Graphix wire (Boston Scientific) was used to re-cross the OM1 branch occlusion. An Apex 2.0 x 12 mm balloon was used to dilate the branch at 18 atm and the sequential limb at 20 atm (Figure 9). The ClearWay 1.5 x 20 mm balloon was then used to deliver intra-graft nitroglycerin (200 mcg) and adenosine (40 mcg). Final angiograms displayed an excellent angiographic result and TIMI-3 flow (Figure 10).

The patient was discharged home in 5 days with significant improvement. A follow-up echocardiogram revealed mild improvement in left ventricular function with an ejection fraction of 45% and significant reduction in mitral regurgitation.

Discussion

Saphenous vein grafts (SVG) have a progressive closure rate, estimated to be 12% to 20% after the first year and almost 50% by 10 years.¹ Repeat CABG carries substantially increased morbidity and mortality rates,² making PCI a more attractive means of revascularization in these degenerated SVGs.³ However, SVG PCI is limited by substantial risk of major adverse cardiac events (MACE) caused primarily by periprocedural myocardial infarction (MI), as a result of no-reflow and distal embolization, which is predictive of late mortality.⁴ Despite the dramatic reduction in periprocedural morbidity with the use of embolic protection devices during SVG intervention,⁵ the MACE rate still remains at 10%, which suggests persistent risk of micro-embolic showers occurring despite embolic protection devices, producing myocardial damage.⁶ Furthermore, studies have implicated increasing graft age⁷, and angiographic characteristics such as presence of thrombus⁸, lesion length⁹, and diffuseness of disease¹⁰ as predictive of adverse events. Previous studies have demonstrated that simple estimators of volume and linear extent of disease burden, including plaque volume and degeneration score, are the most highly predictive factors accounting for adverse 30-day outcomes.¹¹ Plaque burden associated with chronic total occlusions (CTO) of SVG is considerably higher with large and bulky thrombi that tend to occupy the entire length of the graft¹², portending a higher risk of adverse events. This has led to a Class III indication for PCI of SVG CTOs based on current guidelines.¹³ However, in selected cases, SVG revascularization is necessitated by the absence of alternative options^12,14 and has been demonstrated successfully, with ultimate care taken to avoid distal embolization using embolic protection devices and reduction of plaque burden using laser atherectomy.

Despite significant reductions in postprocedural MI with use of embolic protection devices¹⁵, SVG CTOs remain challenging due to an inability to deliver devices, the limitations of poor proximal support and long diffuse lesions, and plaque burden that overwhelms the capacity of current filter devices, prompting the evaluation and need for adjunctive strategies. Meanwhile, studies of SVG PCI performed using intra-graft abciximab have demonstrated significant median percentage diameter stenosis reduction and improvement, and reduction in thrombus grade.¹⁶ This improvement with intra-graft versus intravenous abciximab can be explained by in vitro studies suggesting that achieving 100 times systemic concentration of glycoprotein IIb/IIIa inhibitors leads to thrombo-disruption properties.¹⁷ High local concentration of glycoprotein IIb/IIIa inhibitors achieved with ClearWay-directed delivery in conjunction with laser atherectomy has been demonstrated successfully in case reports as a treatment strategy for PCI of complex SVG.¹⁸

Dr. George can be contacted at: jcgeorgemd@hotmail.com.

*Abbreviations. LIMA: left internal mammary artery; LAD: left anterior descending coronary artery; SVG: saphenous vein graft; OM: obtuse marginal; RCA: right coronary artery.

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Disclosure: Dr. George reports that he is a consultant for Boston Scientific Corporation.