Use of Microvena Snare Catheter in Non-ST Elevation Myocardial Infarction Due to Saphenous Vein Graft Occlusive Thrombi.

Percutaneous coronary intervention of grafts vessel is more challenging due to a higher incidence of periprocedural distal micro-emobilization and myocardial infarction. Percutaneous coronary intervention current guidelines advocate usage of distal embolic protection devices, especially in patients with a large thrombus burden, undergoing percutaneous intervention for vein graft disease. We present a 75-year-old man with acute coronary syndrome who had saphenous vein graft thrombus. This patient was treated successfully by manual aspiration of graft thrombus using a microvena catheter. There is yet no best available therapeutic options for patients undergoing percutaneous coronary intervention of saphenous vein graft lesions.

INTRODUCTION

Saphenous venous grafts may occlude, with or without symptoms. The intimal hyperplasia that develops after venous grafting could be related to surgical trauma, a loss of intrinsic vascular supply, and exposure of the thin-walled structure to an abrupt increase in wall stress as it is moved from low-pressure venous to the high-pressure arterial environment. This leads to subsequent atherosclerotic degeneration and superimposed thrombus, which will give the clinical scenario of stable angina or acute coronary syndrome. Given the risk of injuring other patent grafts and the generally higher risk of re-operation in an older and sicker patient population, percutaneous treatment of diseased and failing saphenous vein grafts is generally preferred[1] and accounts for some 10% to 15% of coronary intervention in most centers.

These interventions present several unique challenges based on the soft and friable nature of the degenerated vein graft lesion, the tendency for distal atheroembolization to produce peri-procedural no-re-flow and myocardial infarction (MI), the frequent association or large thrombi superimposed on critical graft stenosis or recent occlusion, and the high long-term recurrence rate (due to both restenosis at the target site and progression of disease at other sites to cause target vessel failure). Given these multiple challenges, it is natural that catheter management of the diseased saphenous vein graft has been the subject of multiple device development strategies. Although some progress has been made,[2] short-and long-term results remain less favorable than those of native vessel intervention.[3]

CASE PRESENTATION

A 75-year-old male patient known to have diabetes mellitus, hypertension, dyslipidemia, and coronary artery disease underwent coronary artery bypass graft surgery in 2004 left internal mammary artery to left anterior descending artery, saphenous vein graft to right coronary artery and a jump (Y) graft to obtuse marginal 1 and obtuse marginal 2 presented to the emergency department complaining of chest pain and shortness of breath for three days. He was admitted to the coronary care unit as acute coronary syndrome, non-ST elevation MI and started on ACS medication. ECG showed lateral ST-T wave changes and Troponin I was positive, 1.8 ng/ml. The echocardiogram showed moderate hypokinesis of posterlateral wall and the ejection fraction was 50%.

On the second day patient underwent a coronary angiogram, which showed a patent saphenous graft to the right coronary artery; patent left internal mammary artery to left anterior descending artery; and patent Y-graft to obtuse marginal 2 and thrombus in the saphenous graft to obtuse marginal 1 [Figure 1].

Figure 1

Thrombus in the saphenous graft to obtuse marginal 1

Percutaneous intervention was performed using a manual suction technique with a small pediatric microvena snare catheter 4F (ev3, Plymouth, Minnesota. USA). After manual suction few times the graft become clear [Figure 2] and both small organized and fresh clots were removed [Figure 3] and no angioplasty was done in this case. Patient was discharged from the hospital in a very stable condition in a few days.

Figure 2

After manual suction few times the graft becomes clear

Figure 3

Both small organized and fresh clots were removed

DISCUSSION

Acute MI caused by vein grafts thrombosis is an interesting clinical challenge for cardiologists. In patients with a saphenous vein graft as the culprit vessel in acute MI, mortality within one year is 20%.[45] However, recent studies indicate that vein graft MI carry a greater risk of mortality than those involving native coronary vessels, and that previous CABG surgery is an independent predictor of mortality.[4-6]

Saphenous vein grafts exhibit different pathologies at different intervals after operation. Between 3% and 12% of saphenous vein grafts occlude within the first month after bypass surgery.[7] At this early stage, the principal underlying mechanism is graft thrombosis, which is caused by a combination of diffuse endothelial disruptions, changes in blood rheology and alterations in flow dynamics.

Most saphenous vein grafts examined more than two to three months after operation have developed a proliferative intimal fibroplasia. This is not friable, and is rarely a cause of stenosis or occlusion. SVG degenerative disease can simulate native coronary artery disease in clinical presentation and patients with superimpose clots in their SVG can present with ACS, which include STEMI and non STEMI and U/A.

The medical treatment is the same for both native and SVG disease grafts using guidelines and clinical pathways for ACS. The angiography results will determine the way of percutaneous coronary intervention (PCI). If thrombus is detected in the culprit artery or venous graft, there are few ways of treating these lesions such as aspiration or suction methods using aspiration or thrombectomy device. These devices are available commercially, such as export and diver catheters and others.[89] Other methods or treatments are conventional balloon angioplasty, or stents, either BMS or DES and in some cases covered stents.[10]

In some cases a distal protection devices were used or recommended to be used in large vessels with a large clot burden,[11] manual suction using smaller catheters like our case, or using the same guiding catheter with deep engagement,[12] Mechanical thrombectomy devices like Angiojet or X-sizer is still in practice and in use by some of cath labs.[1314]

In few cases were clots are big, invasive cardiologists prefer to use all methods together to minimize the distal embolization and decrease the no reflow phenomenon.

The cornerstone of ACS is stabilization of patients and lesion using aggressive medical therapy including dual antiplatelets therapy Aspirin and clopidogrel and Glycoprotien IIb/IIIa inhibitors in the first 24 hours of patient presentation.

In our case, the patient was treated in the usual manner with anti-ischemic medication in addition to ASA and Plavix; Tirofiban (Aggrastat) was given for 24 hrs prior to angiography. The patient was stabilized medically and his graft angiogram showed a big clot in one of the arms of a Y graft going to OM1 at the proximal segment. We chose to use microvena snare catheter that is mainly used in pediatric cath labs for different purposes. It comes as a snare kit including a snare and a catheter. We used only the catheter because we have used it before in three different adult cases with clots in native coronary arteries and we found that it is one of the least traumatic devices in such cases. Manual suction was applied through this catheter nicely and repeated a few times. The angiographic pictures showed a cleaner SVG after manual thrombus suction.

The optimal strategy for treating these SVG lesions remains unclear. PCI is the best treatment option in ST-segment elevation acute MI. However, contrary to the native vessels, PCI of saphenous vein grafts is associated with serious complications such as distal embolization, no reflow, and slow flow. To overcome these problems, there are embolic protection devices available for eligible patients.

CONCLUSION

Saphenous graft thrombosis is a challenging pathology. It can be removed by available aspiration catheters using a small less traumatic catheter such as the pediatric microvena snare catheter that we used in this patient. The microvena snare catheter is feasible and safe for aspiration of saphenous vein graft thrombus.