A Novel Method of Clot Extraction Using a FilterWire EX‚Ñ¢ in Acute Myocardial Infarction

Acute myocardial infarction (MI) usually results from clot formation due to plaque rupture, platelet aggregation, and activation of the coagulation cascade.^1,2 Contemporary therapy for acute MI involves the timely revascularization by either thrombolytics or percutaneous coronary intervention (PCI) where available.³ PCI for the treatment of acute MI in native coronary arteries is successful in the majority of cases. Distal embolization is a common occurrence, but current techniques have not been very effective in preventing this in the setting of acute MI.⁴ Various techniques for clot extraction have been used with limited success.^5–8 We describe a novel approach for the use of a FilterWire EX™ (Boston Scientific Corp., Natick, Massachusetts) distal protection device as a clot snaring device for successful extraction of a clot that caused acute occlusion of a right coronary artery.

Case Report. A 56-year-old male with hypertension, hyperlipidemia, and tobacco abuse presented with intermittent chest pains of 10 hours’ duration. Electrocardiography showed normal sinus rhythm with Q-waves and 0.5 mm ST-elevation in the inferior leads. He was treated with intravenous nitroglycerin, beta-blockers, heparin, and a glycoprotein IIb/IIIa inhibitor. A diagnostic left heart catheterization demonstrated total occlusion of the distal right coronary artery with a large thrombus burden (Figure 1).
A FilterWire EX embolic protection system was then introduced into the right coronary artery and the filter was deployed after crossing the clot (Figure 2 A). The deployed filter was then pulled back proximally in the open configuration with entrapment of the clot (Figure 2 B). The FilterWire EX was retrieved in the usual fashion, and a large clot was recovered (Figure 3) with immediate restoration of TIMI 3 flow and uncovering of a discrete, severe distal right coronary artery stenosis (Figure 4 A). This was treated with a 3.5 mm x 13 mm Cypher™ sirolimus-eluting stent (Cordis Corp., Miami, Florida), and postdilated with a 4.0 mm x 8 mm noncompliant balloon with good angiographic results and TIMI 3 flow (Figures 4 B and C). The patient tolerated the procedure very well and had an uneventful hospital course. His CPK, CPK-MB and troponin levels peaked at 2,699 U/L, 164 ng/ml, and 265 ng/ml, respectively just before the PCI, and trended downward and normalized after the PCI. A two-dimensional transthoracic echocardiogram performed after the PCI showed a left ventricular ejection fraction of 50% with hypokinesis of the inferior and infero-septal walls.

**i**Discussion. In cases of acute MI with a large clot burden, interventionalists use a myriad of techniques such as multiple balloon inflations followed by stenting, intracoronary thrombolytics, or glycoprotein IIb/IIIa inhibitor administration, and AngioJet^®(Possis Medical, Inc., Minneapolis, Minnesota) or Express catheter (Boston Scientific) suction devices.^1,5–8 None of these techniques is ideal and further challenges are encountered with subacute and organized clot formation, resulting in incomplete or partially successful results, distal embolization, no-reflow, and infarct extension.⁴ Frequently, a previously healthy segment of the coronary artery, remote from the site of stenosis or plaque rupture, suffers injury due to these techniques, requiring multiple stents to cover additional segments of the coronary artery. This carries with it higher complication rates of restenosis, acute, and subacute thrombosis.
The use of filter protection systems during saphenous vein graft and native coronary artery interventions reduces distal embolization, microvascular obstruction, and no-reflow, resulting in a lower incidence of postprocedural major adverse coronary events.^9–12 The safety and feasibility of the FilterWire EX device have been demonstrated in large and small coronary arteries.^13,148,15 The FilterWire EX device has rarely been used to retrieve clots responsible for acute native coronary artery occlusions. Yang et al used the FilterWire EX distal protection device to retrieve a large refractory thrombus in a native coronary artery after drug-eluting stent implantation.16 Our novel approach of clot-snaring with the FilterWire EX device can potentially prevent distal embolization and achieve excellent clot extraction, especially in the setting of acute coronary occlusion with a large clot, as demonstrated in our case. There may be some concern about positioning the angioplasty wire in the distal coronary artery after retrieval of the FilterWire EX device. This may be avoided by deploying an angioplasty wire in the distal segment before crossing the lesion with the FilterWire. This way, once the clot is retrieved via the FilterWire, access across the lesion is still maintained. Some potential complications of positioning a filter device distal to a lesion and pulling it proximally to trap the thrombus include damaging the normal vessel with the filter, sticking of the filter on severe and calcified lesions underlying the thrombus or recently deployed proximal stents, or clot reembolization in the same vessel or in a major branch. Additionally, the filter might not be deliverable in tortuous, calcified, or small vessels or in vessels with distal lesions or lesions at branch points. In our opinion, the vessels best suited for thrombus extraction using the FilterWire include nontortuous and medium-to-large sized vessels where the lesions are not very distal or involve branch points. An alternative to our method involves deploying a FilterWire for distal protection prior to deployment of clot extraction devices to reduce embolization from the passage of these devices. Distal protection systems such as balloon occlusion and aspiration devices or distal filters have been successfully used for distal protection during PCI of native coronary arteries in the setting of acute MI, with improvements in markers of myocardial reperfusion and left ventricular function in some studies^4,5 and no significant improvement in microvascular flow, reperfusion success, infarct size reduction, left ventricular function, or event-free survival in other studies.

Conclusion. We propose a novel method that utilizes a FilterWire EX device for clot extraction, while protecting against distal embolization and preventing injury to the native coronary artery distal to the occlusion. A series of patients is needed to further establish the feasibility and safety of this novel approach of clot extraction.

References

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