Catheter-Directed Intra-Graft Thrombolysis and Aspiration Thrombectomy for Subacute Saphenous Vein Graft Occlusion

Abstract

Primary percutaneous coronary intervention is the preferred strategy for reperfusion in the treatment of acute myocardial infarction due to superior outcomes compared to fibrinolytic therapy. However, acute myocardial infarctions involving saphenous vein graft occlusions are deemed to portend a higher risk of intervention. We present a case of subacute myocardial infarction with saphenous vein graft occlusion managed successfully with catheter-directed intra-graft thrombolysis and aspiration thrombectomy to reduce the risk of embolization and limit the zone of treatment.

Case

A 78-year-old male with known coronary artery disease and prior coronary artery bypass grafting (CABG) presented with non ST-segment elevation myocardial infarction (NSTEMI). Physical examination was unremarkable and laboratory analysis confirmed recent MI with troponin of 27. Electrocardiogram revealed 1 mm ST-segment depressions in the inferior leads. Coronary angiography revealed a saphenous vein graft (SVG) to distal right coronary artery (RCA) with proximal 100% thrombotic occlusion (Figure 1).

A 6 French AR1 guide was used to engage the SVG->RCA graft.  A Prowater wire (Asahi Intecc) was advanced across the lesion into the distal RCA. A ClearWay 1.0 x 10 mm perfusion balloon (Atrium) was then used to deliver intra-graft tPA (2 mg bolus) in the proximal graft (Figure 2) and subsequent nitroglycerin (200 mcg) in the distal graft with improvement in flow after 2 minutes of dwell time and layering of thrombus within the distal graft (Figure 3). An Xpressway catheter (Atrium) was used to perform aspiration thrombectomy (Figure 4) throughout the length of the graft with retrieval of large amount of thrombus adherent to the tip of the catheter (Figure 5). Subsequent angiogram revealed the likely culprit site of initial thrombotic occlusion within the graft, which was a distinct distal zone in the mid body of the graft (Figure 6) away from the proximal site of occlusion. A Promus 3.0 x 16 mm drug eluting stent (Boston Scientific) was deployed selectively at this site and post-dilated using an NC Sprinter 3.25 x 12 mm non-compliant balloon (Medtronic). Final angiogram revealed brisk TIMI-3 flow through the stented segment and graft with an excellent angiographic result (Figure 7).  

The remainder of the hospital stay was uncomplicated. The patient was discharged home in 2 days with indefinite dual antiplatelet therapy of aspirin and ticagrelor.  

Discussion

Early and complete reperfusion is the most important goal in treatment of patients with acute MI.¹ Primary percutaneous coronary intervention (PCI) is the preferred strategy for reperfusion in the treatment of STEMI, due to superior outcomes compared to thrombolytic therapy.²  

SVGs have a progressive closure rate, estimated to be 12% to 20% after the first year and up to 50% by 10 years.³ However, SVG PCI is limited by substantial risk of major adverse cardiac events caused primarily by periprocedural MI, as a result of no-reflow and distal embolization that is predictive of late mortality.⁴ Despite the dramatic reduction in periprocedural morbidity with the use of embolic protection devices (EPD) during SVG intervention⁵, the MACE rate still remains at 10%, which suggests persistent risk of micro-embolization occurring despite EPD, 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 and thrombus burden of SVG is considerably higher with acute MI, involving large and bulky thrombi in the proximal graft that tend to occupy the entire length of the graft, portending a higher risk of adverse events. Moreover, the lack of visibility of the distal graft in the setting of proximal graft occlusion proves to be technically challenging for the placement of an EPD.

The optimal pharmacologic therapy for reperfusion before and in conjunction with primary PCI has evolved over time. Recently, adjunctive PCI with intracoronary catheter-directed delivery of glycoprotein IIb/IIIa inhibitor has been shown to reduce infarct-size in patients with large anterior STEMI¹², suggesting a benefit of localized high-dose delivery of the adjunctive pharmacologic agent. 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.¹³ 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.¹⁴ High local concentration of glycoprotein IIb/IIIa inhibitors achieved with ClearWay-directed delivery in complex SVG occlusions has been demonstrated previously.¹⁵ Moreover, ClearWay-directed thrombolysis has also been demonstrated successfully, when refractory to conventional treatment strategies.¹⁶

Herein, we present a patient with acute MI secondary to proximal SVG thrombosis that was successfully revascularized using catheter-directed thrombolysis and aspiration thrombectomy. This approach demonstrates an alternative strategy to minimize embolization and limit the zone of treatment, especially when the placement of EPD is technically challenging.

Disclosure: Dr. George reports he is a consultant to Boston Scientific and receives research support from Atrium Medical.

Dr. Jon George can be contacted at: jcgeorgemd@gmail.com

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