Extensive Thrombus of Distal Anastomosis of Saphenous
Vein Graft

Case Report. The patient was a 76-year-old male with the cardiovascular risk factors of hypertension and hyperlipidemia. His cardiovascular history began in April 2000, with a myocardial infraction (MI) of the anteroseptal wall; although, he was managed conservatively. Four months later, the patient presented with an acute reinfarction of the anteroseptal wall, and was experiencing post-MI angina. Diagnostic cardiac catheterization revealed triple vessel disease. The patient underwent double coronary artery bypass graft (CABG) surgery. A saphenous vein graft (SVG) was inserted on the left anterior descending artery (LAD) and another SVG was inserted on an obtuse marginal (OM) branch; the right coronary artery was not considered suitable for revascularization. The patient remained asymptomatic until July 2001. He was taking aspirin (250 mg/day) and atenolol (100 mg/day) when he was admitted for unstable angina (Braunwald’s class IIIB), accompanied by transitory supraventricular tachycardia segment elevation in the anterior leads, and a rise in troponin T (0.6 ng/mL; upper normal limit, 0.1 ng/mL). The patient underwent diagnostic cardiac catheterization which revealed a left ventricular ejection fraction of 50%, moderate anterolateral and apical hypokinesis, triple vessel disease of the native coronary arteries, and SVG to the OM. The SVG to the LAD presented a large thrombus in its distal anastomosis; the thrombus burden extended to the native coronary artery, with TIMI III flow (Figure 1). Patient management. Coronary revascularization was not performed due to the presence of extensive thrombus burden with no angiographic evidence of SVG wall disease. A 300 mg loading dose of clopidogrel was administered, as was a treatment with the glycoprotein IIb/IIIa inhibitor abciximab (0.25 mg/kg bolus and 10 m/min infusion for 12 hours). This was initiated with the goal to obtain resolution of the thrombus burden; therefore, abciximab infusion was maintained for 12 hours. The patient continued treatment with unfractioned heparin (activated partial thromboplastin time (aPTT) 2.0–2.5 times normal value), aspirin (250 mg/day), and atenolol (100 mg/day). The following day, a coronary arteriography was performed, but no signs of thrombus resolution were observed (Figure 2). In the absence of symptoms over the previous 72 hours, and due to the high risk of distal embolization accompanied by technical difficulty of coronary revascularization in this setting, the procedure was postponed for one week. The patient continued treatment with unfractioned heparin, aspirin, atenolol, and clopidogrel (75 mg/day). Coronary arteriography was performed the following week, and the procedure revealed complete thrombus resolution, with no angiographic evidence of residual stenosis (Figure 3). Due to the appearance of an extensive thrombus at the site of the distal anastomosis in a relatively recently inserted SVG of less than one year, and with no angiographic evidence of disease of the vessel wall, this was considered a case of “vein thrombosis;” therefore, treatment with warfarin was initiated. The international normalized ratio (INR) was between 2–3; therefore the patient was discharged with the recommendation to maintain treatment with warfarin, aspirin, and atenolol for at least six months. At five months of clinical follow-up period, the patient was asymptomatic. How Would You Manage This Case? David Ramsdale, MD The Cardiothoracic Centre - Liverpool Liverpool, United Kingdom The saphenous vein graft (SVG) appears to be ectatic with an irregular lumen along its length and the variation in opacity suggests that there may be more thrombus within the graft than just the large collection distally. The left anterior descending coronary artery appears to be of small calibre in comparison to the SVG and this together with the position of the distal thrombus probably makes the deployment of a distal protection device impractical. I would favour using a combination of aspirin, clopidogrel and abciximab (intragraft bolus plus intravenous infusion over 12 hours — as the authors describe) plus intragraft rtPA (100 mg over 20 minutes) —- with the patient then maintained on intravenous heparin over the next 48 hours with an ACT between 250–300 seconds. If a repeat angiogram at 48 hours did not show any resolution of thrombus then it would be reasonable to remove the thrombus using a thrombectomy device such as a 2.0 mm or 2.3 mm X-SIZER™ catheter (EndiCOR Medical Inc., San Clemente, California). Relatively early thrombosis occuring in such an ectatic SVG does not bode well for the sustained patency of the graft. Long-term anticoagulant therapy with warfarin together with low-dose aspirin (75 mg daily) would be my treatment of choice. John G. Webb, MD Interventional Cardiology Research St. Paul’s Hospital Vancouver, British Columbia, Canada The authors document that anticoagulation alone resulted in clot dissolution. Had they not resisted the temptation to intervene, distal embolization and no-reflow might have resulted in a very unpleasant procedure. Nevertheless, it is worth discussing newer device options should recurrent ischemia have forced their hands. Mechanical thrombectomy devices, particularly the Angiojet,™ but possibly also the Hydrolyzer,™ X-SIZER™ catheters may effectively debulk thrombus. Recently the Export™ manual aspiration catheter (without the accompanying GuardWire™ balloon) has gained some popularity, although it may be less effective in breaking up large thrombi. With these devices distal embolization remains a concern during wire passage and all disrupted thrombus may not be aspirated. Distal protection, with an occlusive balloon or filter, may be desirable but is associated with a significant risk of embolization during passage of the wire or device across the lesion. The small caliber of the distal LAD landing zone would compromise deployment of currently devices which are designed for larger vessels. An additional concern would be the tendency to redirect flow (and therefore emboli) up the unprotected proximal LAD. Proximal protection has some appeal. We have utilized the Velocimed Proxis™ and the Kerberos™ embolic protection systems. Both occlude the proximal vessel with a balloon prior to distal wire passage and intervention. Embolic material is aspirated prior to restoration of flow, potentially addressing some of the limitations of alternative approaches. In this particular case the passage of time was apparently the best therapy. James P. Zidar, MD Associate Professor of Medicine Duke Cardiology of Raleigh Raleigh, North Carolina This case represents a clinical challenge of an elderly patient with a recent vein graft bypass. He presents with unstable angina less than one year after his bypass. It is unclear why the patient did not receive a LIMA to his LAD. He is at risk for thrombus in this graft due to the significant size mismatch between the large ectatic vein and the small caliber of the distal LAD. The management of this case was outstanding and produced a beautiful result using IIb/IIIa inhibitor and prolonged heparin. However, this required in-hospital IV heparin for one week after giving a bolus and 12-hour infusion of abciximab with little change. If the thrombus burden was more proximal in the vein graft ad not at the distal anastomosis, I would have tried a distal protection approach and attempted to suck out the clot with the Export catheter from Medtronic. Given the location of the thrombus and the fact that the patient was not having ongoing ischemia, a conservative strategy is quite reasonable. I also would bolus the patient with clopidogrel, as was done, and treat the patient with a bolus and 12-hour infusion of abciximab. I might have hastened the dissolution of thrombus after initiation of abciximab with a half-dose of lytic therapy, giving half the initial dose directly into the vein graft and giving the other half systemically. I would have left the patient on heparin overnight and reevaluated the patient the following day. If the thrombus was dissolved, the patient might have been spared an extra week in the hospital. Nonetheless, the strategy employed by the investigators was more conservative, with a prolonged course of heparin and an impressive resolution of his extensive thrombus one week later. The strategy of long-term coumadin is reasonable in this case, which would be equivalent to coronary ectasia, given the disparity in size between the distal vein graft and the distal LAD. Larry J. Diaz-Sandoval, MD and Ik-Kyung Jang, MD The Knight Center for Interventional Cardiovascular Therapy Massachusetts General Hospital, Harvard Medical School Boston, Massachusetts Although it is definitely difficult to argue with success, there are several issues in the management of this case that need to be addressed: 1) Implantation of a saphenous venous graft to the LAD is currently considered a sub-optimal treatment. It would be of interest to know why this patient did not receive a left internal mammary artery graft. 2) The use of abciximab to obtain resolution of the thrombus burden in a saphenous venous graft has not been systematically studied. Sub-group analysis of patients from the EPIC study demonstrated that the use of abciximab does not improve the outcomes of interventions in saphenous venous grafts,¹ and the strategy described by the authors in this case is only supported by a small report on five patients.² 3) After 24 hours the original strategy did not work and then the patient was kept in the hospital for one week, receiving unfractionated heparin. This strategy substantially increases the cost of hospitalization and the cost of laboratory analyses that were required to monitor the appropriateness of the anticoagulation regime. This is indeed a difficult case that represents a rather common dilemma in the daily practice of interventional cardiology, and that has no straight answer based on the available evidence. Given the distal location of the thrombus, the use of distal protection devices was not an option. In this setting, rheolytic thrombectomy with the use of the AngioJet catheter (AngioJet, Possis Medical Inc., Minneapolis, Minnesota) could have been considered.³ The common practice at our institution is to continue intravenous unfractionated heparin and a GP IIb/IIIa inhibitor administration for two to three days in order to stimulate endogenous thrombolysis. If the repeat angiogram at that time reveals significant thrombus burden, then we proceed to perform rheolytic thrombectomy. We would also have sent a battery of laboratory tests to determine whether this patient had a hypercoagulable state, which would have allowed us to take the appropriate prophylactic and therapeutic measures.