Unique Successful Thrombolytic Therapy in Saphenous Vein Graft

Abstract

Saphenous vein graft (SVG) percutaneous coronary intervention (PCI) is a valuable interventional procedure often performed in the cardiac catheterization laboratory. SVGs are susceptible to atherosclerotic occlusions and blockages that can lead to acute cardiac problems or chronic occlusions and angina. PCI in occluded grafts has many associated risks that range from acute myocardial infarction to procedural failure and vessel dissection. PCI in occluded grafts is not encouraged due to its high risks, potential for worse outcomes, and lack of established interventional procedures. In this case report, we present a unique case of an SVG to obtuse marginal I (OM1) occlusion that was successfully treated with an alternative thrombolytic intervention followed by aspiration. 

Saphenous vein graft occlusions have been a significant problem in the realm of interventional cardiology. Maintaining patency of SVGs over time is difficult due to recurrent and frequent occlusions in the graft. SVG occlusions occur in 40% of patients on average during the first 10 years post coronary artery bypass graft surgery (CABG) and recurrence of occlusions in these grafts post intervention occurs in 15% of patients within the first year.¹ Many studies have associated SVG occlusions with both acute and chronic cardiovascular events such myocardial infarction (MI), angina, and even death. SVG pathology differs from normal coronary disease due to the presence of friable atheroma, lacking an organized fibrous cap, which can lead to distal emboli upon interventional equipment manipulation.²

Despite its low patency rate, SVG intervention continues to be a major subset of the PCIs performed in the cardiac catheterization laboratory. According to a report from the American College of Cardiology National Cardiovascular Database’s CathPCI registry, SVG interventions represent 5.7% of all PCIs between 2004-2009.1 There is a significant need for more clinical data to support better treatment options for SVG occlusion.

Different approaches in the treatment of SVG failure have been developed. One is redo-CABG surgery, linked to an increase in mortality when compared to the initial surgery.³ As a result, this approach has been characterized as a last resort. There have been clinical trials comparing treatment approaches in SVG occlusions. The Saphenous Vein De Novo (SAVED) trial compared balloon angioplasty with bare metal stents in SVGs, concluding that bare metal stents offer more benefits and fewer complications, with a high success rate and lower mortality rate.⁴ 

Case

A 49-year-old male presented to the emergency room complaining of chest pain. He was found to have positive troponins and was diagnosed with non-ST-elevation MI (NSTEMI) based on electrocardiogram (EKG) criteria. The patient had a history significant for pulmonary embolism, hypothyroidism, hypertension, diabetes mellitus, and ischemic cardiomyopathy with an implantable defibrillator. He had undergone CABG surgery with 4 bypass grafts and a subsequent 7 stents. The patient was dry heaving and diaphoretic upon admission. He complained of having dyspnea on exertion over the past 1-2 months. In the emergency department, he was twice given nitroglycerin sublingually with minimal relief.  Afterwards, 2 mg of morphine was administered, resulting in moderate pain improvement. This was followed by placement of a nitroglycerin drip. The patient was then taken urgently to the catheterization laboratory for cardiac angiography. Catheterization revealed a 100% occlusion of the proximal right coronary artery (RCA), occluded stents in the proximal left anterior descending (LAD) coronary artery, and an occluded SVG-OM1 graft at the mid portion (Figure 1). Initially, balloon angioplasty was attempted in the occluded vein graft, but the blockage did not resolve (Figure 2). Aspiration thrombectomy via an Export aspiration catheter (Medtronic) was attempted without success. AngioJet rheolytic thrombectomy (Boston Scientific), a stronger aspirating technique, was attempted (Figure 3), and once again, the occlusion did not resolve (Figure 4). 

Following these attempts, it was decided that a unique and desperate approach, utilizing thrombolytic therapy, would be attempted to relieve the occlusion. A 2 mg aliquot of alteplase was administered via a single infusion. Heparin was also subsequently administered with the alteplase infusion. The aliquot was left to dwell on the occlusion for 10 minutes and then aspiration was attempted once again, after which the occlusion was resolved. Angiography post aspiration confirmed occlusion resolution and restoration of blood flow through the SVG (Figure 5). 

Discussion

The impetus of this case report arose from the diagnosis of a saphenous vein graft occlusion. Risk factors of SVG occlusion include but are not limited to smoking, hypertension, and hyperlipidemia.⁵ These risk factors mirror those of native coronary disease, but their effects are much more prominent in grafts due to the inherent deficiencies of a vein graft as a conduit for coronary circulation. In a study conducted to observe graft occlusion phenomena, 87 patients underwent CABG surgeries between 1996 and 2001. Twenty-six patients (29.9%) had a vein graft occlusion at 8.0 ±1.1 years. The significant likelihood of occlusions in vein grafts demonstrates the need for therapy to resolve these occlusions, restore the integrity of grafts such as SVGs, and avoid redo CABG.  

Several studies have evaluated therapeutic interventional techniques used to relieve graft occlusions and evaluate their respective outcomes. In a meta-analysis conducted in 2012, clinical outcomes of different therapies used in SVG PCIs were analyzed. The most commonly utilized therapy was the use of drug-eluting stents (DES). When compared to bare metal stents, DES were associated with a reduction in the rate of repeat occlusion.⁶ 

Although using thrombolytic therapy in vein grafts has been documented previously, our case report highlights the value of aspiration post-thrombolytic therapy in relieving the occlusion and preventing additional thromboembolic events. The approach used in this case offers a novel technique to relieve SVG occlusions in acute and non-acute settings, providing an option to revascularization of the native anatomy. This technique has been commonly used intracoronary to resolve native coronary occlusions. Multiple case reports and studies have shown the success of thrombolytic therapy in treating coronary artery thrombosis.⁷ Thrombolytic therapy has often been preferred over aspiration thrombectomy due to a decreased risk of distal embolism as a subsequent complication.4 Utilizing aspiration post thrombolytic therapy decreases the likelihood of no-reflow as well as decreases the amount of debris that can cause further emboli, making it a valuable approach to PCI. As presented in this case, aspiration post thrombolytic therapy may offer potential for treating complex graft thrombosis as well as protection against thrombotic events. 

Conclusion

Saphenous vein graft occlusion is a significantly reported complication of cardiac bypass graft surgery, with a reported 40% incidence at 10 years post CABG. There have been many studies comparing the different interventions performed in cases of vein graft occlusion. The most common is the use of drug-eluting stents, but this technique cannot always resolve graft occlusions and can result in distal emboli. The successful outcome of this case underscores the importance of and benefit to exploring other alternative interventions, such as the use of thrombolytic treatment via alteplase infusion and aspiration in patients with SVG occlusions. More evidence-based studies are required to demonstrate the effectiveness of unique approaches for intervention in acute cases.

References

1. Hindnavis V, Cho SH, Goldberg S. Saphenous vein graft intervention: a review. J Invasive Cardiol. 2012; 24: 64-71. 
2. Cook J, Uretsky BF, Sachdeva R. Intervention in the occluded vein graft: with high risk can come great reward. Review of techniques with case examples. J Invasive Cardiol. 2012; 24: 612-617. 
3. Cameron A, Kemp HG Jr, Green GE. Reoperation for coronary artery disease. 10 years of clinical follow-up. Circulation. 1988; 78: I158-I162.
4. Savage MP, Douglas JS Jr, Fischman DL, et al. Stent placement compared with balloon angioplasty for obstructed coronary bypass grafts. Saphenous Vein De Novo Trial Investigators. N Engl J Med. 1997; 337: 740-747.
5. Motwani JG, Topol EJ. Aortocoronary saphenous vein graft disease: pathogenesis, predisposition, and prevention. Circulation. 1998; 97(9): 916-931.10.1161/01.CIR.97.9.916
6. Alam M, Bandeali SJ, Virani SS, Jneid HM, et al. Clinical outcomes of percutaneous interventions in saphenous vein grafts using drug-eluting stents compared to bare-metal stents: a comprehensive meta-analysis of all randomized clinical trials. Clin Cardiol. 2012; 35: 291-296. doi:10.1002/clc.21984
7. Bitigen A, Gurel E, Tanalp AC, Aung SM, Başaran Y. Acute anterior myocardial infarction due to aortosaphenous vein graft occlusion with very large thrombus burden. Exp Clin Cardiol. 2007 Winter; 12(4): 203-205.

Disclosures: The authors report no conflicts of interest regarding the content herein.
The authors can be contacted via Pratik Patel, MD, at ppatel@cminj.com