Facing the Intracoronary Thrombus Burden: The Two-Step Approach to Coronary Stenting

Introduction

Coronary stenting is recommended as the treatment of choice for ST-elevation myocardial infarction (MI) and is not only effective in opening the infarct-related artery (IRA) but also reduces re-occlusion and restenosis.¹ However, in many patients with acute coronary syndrome, it is not uncommon to encounter a large thrombus burden during coronary angiography. When implanted in a high thrombotic milieu, coronary stents may be associated with distal embolization, impaired microvascular flow and increased peri-procedural complications.^2-3 Thrombus aspiration alone without angioplasty or stenting is reported to be effective, especially in cases where an occlusive lesion is absent.^4-6 However, cases with an underlying coronary stenosis often pose a therapeutic challenge to interventional cardiologists. 

The option of deferred coronary stenting with interim lesion passivation using adjunctive antiplatelet/antithrombotic treatment has been suggested in these  patients.^7-8 This can potentially lead to resolution/reduction of the intracoronary thrombus, thereby limiting the risk of embolization during subsequent stenting and also avoid stenting in cases where the check angiogram shows absence of a significant coronary stenosis. We describe two such cases, wherein a high thrombus burden during the diagnostic coronary angiogram led to a strategy of deferred coronary stenting. Both patients received glycoprotein (GP) IIb/IIIa antagonists, low-molecular-weight heparin, and routine dual-antiplatelet therapy. Repeat angiography within 48-72 hours of the initial procedure revealed complete resolution of the intracoronary thrombus in one patient, while in the other, the thrombus burden had significantly reduced. While in the first patient, no coronary intervention was needed, successful coronary angioplasty with stenting was performed in the second patient. 

Case 1. A 48-year-old chronic smoker, nondiabetic, normotensive male presented with acute anterior wall ST elevation MI. A coronary angiography had been performed at an outside institution and revealed a large, grade 4 thrombus⁹ in the ostial left anterior descending (LAD) artery, extending into the proximal and mid LAD (Figure 1, Video 1). The left circumflex (Cx) and right coronary artery (RCA) were normal. Since the large ostial thrombus in the LAD was deemed to represent a high risk to immediate coronary angioplasty and stenting, the procedure was deferred, and the patient referred to our institution for further management after being put on low-molecular-weight heparin. On presentation, the patient had no ongoing chest pain and the electrocardiogram (ECG) showed resolution of the ST elevation. The patient was administered an eptifibatide infusion for 18 hours and repeat coronary angiography was planned 48 hours after the initial procedure. The idea was to achieve adequate lesion passivation using adjunctive antiplatelet/antithrombotic treatment, but at the same time, be prepared to do an immediate angioplasty if needed. The patient remained asymptomatic and angiography after 48 hours revealed complete resolution of thrombus without any residual coronary stenosis and TIMI-3 flow in the LAD, thus obviating the need for stenting (Figure 2, Video 2).

Case 2. A 46-year-old chronic smoker, diabetic, normotensive male presented with inferior wall ST elevation MI and was taken up for primary coronary angioplasty at our institution. Coronary angiography revealed a normal LAD and left circumflex (Cx), with mid total occlusion (grade 5 thrombus⁹) of the right coronary artery (RCA) with a large thrombus burden (Figure 3A-B, Video 3). The lesion was crossed with a .014-inch Whisper wire (Abbott Vascular) and repeated attempts at aspiration of the thrombus were made, using a 6 French (Fr) Export AP aspiration catheter (Medtronic). However, despite all attempts, including dilating with an undersized balloon (1.5 or 2.0 mm in diameter), the residual coronary thrombus burden was very high, with only TIMI-1 flow in the artery (Figure 4A-B). Since no other thrombectomy devices (including an AngioJet [Medrad]) were available on-shelf and the thrombus burden was deemed too high for an immediate stenting, we opted for a strategy of deferred stenting. The patient received an abcximab bolus followed by infusion for 18 hours along with low-molecular-weight heparin and dual anti-platelet therapy. Repeat angiography after 72 hours revealed significant reduction in the thrombus burden with an underlying severe stenosis in the mid RCA (Figure 5A-B).The lesion was rewired and easily stented using a Pronova XR (4.0 x 28 mm) coronary stent (Vascular Conception, Bangalore, India) with good result and TIMI-3 flow (Figure 6A-B).

Discussion

Patients with acute coronary syndrome (especially those with ST elevation MI) often have a high intracoronary thrombus burden. In most cases with a significant coronary thrombus, the standard procedural protocol involves aspiration of thrombus or mechanical thrombectomy, followed by balloon dilation if needed, and subsequent coronary stenting. However, coronary stenting in a high thrombotic milieu may be associated with distal embolization of the thrombus, microvascular obstruction, slow flow and increased procedural complication.^2-3 Thrombus aspiration alone without angioplasty or stenting as the sole revascularization technique is reported to be safe and effective, especially in cases where an occlusive lesion is absent.^4-6 However, the optimal management of patients with a large coronary thrombus and underlying coronary stenosis poses a therapeutic challenge. In the first case described, the large ostial thrombus in the LAD was considered a high risk to immediate stenting. Treatment with low-molecular-weight heparin and eptifibatide led to complete resolution of the thrombus, without any residual lesion in the LAD, and hence obviated the need for stenting. In the second case, multiple attempts at manual aspiration of the thrombus and balloon dilatation was ineffective in significantly reducing the thrombus load. Since we did not have other thrombectomy devices, such as an AngioJet, available to us in the lab, coronary stenting was deferred and the patient received an abciximab infusion and low-molecular-weight heparin. This led to significant reduction in the thrombus burden, facilitating implantation of a coronary stent without any complications. The option of deferring stenting of lesions with a large thrombus burden until normal anterograde flow is established, either after manual or mechanical thrombectomy or intensive medical post-conditioning, has its merits. Treatment in the interim with GP IIb/IIIa inhibitors, heparin (unfractionated or low-molecular-weight), and dual antiplatelet therapy decreases the thrombus burden and enhances the procedural safety of subsequent coronary stenting. Although this approach may theoretically increase the risk of reocclusion in patients who are left unstented, the risk is low, and whether this outweighs the postulated benefits needs to be studied in larger trials.^7-8  

We also believe that such a strategy is unlikely to significantly prolong hospital stays.  As a policy, we discharge most patients with acute coronary syndrome undergoing coronary angioplasty within 24-48 hours (as most of the procedures are performed by the radial route), while patients with ST elevation MI are discharged within 3-5 days. In the cases herein, both patients were also discharged within 3-5 days.

The advantage of such a two-step strategy is that it can not only reduce the risk of adverse events such as no-reflow or distal embolization, but often stent implantation may not be necessary, as the lesion is often found to be non-occlusive during check angiography. 

Conclusion

A strategy of deferred stent implantation may be useful in selected patients with high intracoronary thrombus burden in the IRA. Interim medical post-conditioning using adjunctive antiplatelet/anti-thrombotic therapy may not only help reduce the thrombus load, thereby minimizing procedural complications, but can also avoid unnecessary stenting in patients with non-occlusive stenosis. Large-scale randomized trials need to be performed in this group of patients to further document the safety and efficacy of this technique.

Disclosure: None of the authors report any financial relationships or conflicts of interest regarding the content herein.

This article received a double-blind peer review from members of the Cath Lab Digest Editorial Board.

The authors may be contacted via Dr. Aditya Kapoor at akapoor65@gmail.com. 

References

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