Left Main Thrombus as a Complication of Thrombectomy During Primary Percutaneous Coronary Intervention

ABSTRACT: Small randomized trials in patients with ST-elevation myocardial infarction have shown that aspiration thrombectomy improves angiographic outcomes and may improve clinical outcomes. However, there remains a lack of reports on device-related complications. We report a case of a device complication involving the left main coronary artery where a large burden of thrombus was brought back into the left main coronary artery from the circumflex during aspiration thrombectomy.

In patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI), small randomized trials have shown that manual thrombus aspiration devices improve angiographic outcomes and may lead to improved clinical outcomes, but a large multicenter trial is lacking.^1,2 Furthermore, a meta-analysis of randomized trials has suggested possible reduction in mortality but with a trend for possible increased stroke rate.³ As a result of these small trials, the use of aspiration thrombectomy during primary PCI is growing rapidly.

However, there may be underreporting of device-related complications to thrombectomy catheters. In a recent meta-analysis of 11 trials, 6 trials did not report device-related complications.² Furthermore, there are no published case reports of left main coronary artery (LMCA) thrombus as a complication of manual aspiration thrombectomy during STEMI, to our knowledge.

We describe a case of primary PCI for acute stent thrombosis in which aspiration thrombectomy brought a large amount of thrombus from the circumflex into the LMCA, resulting in a life-threatening complication.

Case Report. A 49-year-old man presented to a community hospital with acute inferolateral STEMI and was treated with tenecteplase, unfractionated intravenous heparin, aspirin and clopidogrel (300 mg loading dose). The patient was transferred to a tertiary care facility. On arrival, there was resolution of ST elevation, suggesting the patient had clinically reperfused. The patient was taken to the cardiac catheterization laboratory several hours later and coronary angiography showed a patent LMCA, 50% stenosis of the distal segment of the left anterior descending artery (LAD), hazy 75% stenosis in the middle segment of the left circumflex artery (LCX; culprit lesion) and a dominant right coronary artery (RCA) with mild luminal irregularities. Activated clotting time (ACT) was 172 seconds and an additional 2,000 units of heparin were given intravenously. PCI was performed with direct stenting of the LCX lesion with a 3.0 x 23 mm Vision™ (Abbott, Abbott Park, Illinois) bare-metal stent (BMS) deployed at high pressure. No glycoprotein IIb/IIIa inhibitor was used due to concerns regarding bleeding risk after full-dose fibrinolytic therapy. The patient had been pretreated with a 300 mg loading dose of clopidogrel approximately 6 hours before PCI. Thereafter, TIMI 3 flow down the distal vessel was observed and the patient was transferred back to the Coronary Care Unit (CCU) for observation.

Two hours later, the patient had recurrence of his chest pain with 4 mm of new ST-segment elevation in the lateral leads. The patient was transferred urgently to the catheterization lab. Coronary angiography was performed via the radial approach and showed acute stent thrombosis with a thrombotic occlusion of the stent within the proximal LCX (Figure 1A). A 6 French (Fr) Voda left 3.5 guiding catheter was used to engage the LMCA. Abcximab (bolus dose of 0.25 mg/kg) was given intravenously and ACT was 150 seconds; therefore, an additional 4,000 units of unfractionated heparin were given. A BMW wire was advanced to the distal segment of the LCX. We then dilated with a 2.5 x 15 Voyager balloon, which resulted in a TIMI 2 flow. Due to concerns of possible edge dissection proximally, we then placed a 3.5 x 12 Vision™ BMS, overlapping proximally with the previously deployed stent. After deployment of the stent, there was severe no reflow and a large amount of thrombus within the circumflex artery. A repeat ACT was 360 seconds and no additional heparin was given. Repeated doses of intracoronary nitroprusside were given and aspiration thrombectomy was performed with a Pronto V3™ catheter (Vascular Solutions, Inc., Minneapolis, Minnesota). Repeated aspirations were performed with a Pronto V3™ catheter (Vascular Solutions, Inc.) within the circumflex. Negative suction was continued during removal of the aspiration catheter.

After removal of the Pronto catheter, a new, large, mobile filling defect in the LMCA was observed (Figure 1B), which likely represented thrombus brought back from the LCX into the LMCA. We then attempted to remove the LMCA thrombus with the guide catheter by aspirating multiple 30 cc syringes without success. Finally, we used a new Pronto V3 catheter and aspirated within the LMCA and LCX arteries. We were unsuccessful in removing the thrombus but were able to push the thrombus back into the LCX such that the LMCA filling defect resolved, but the LCX re-occluded with TIMI 0 flow (Figure 1C). Then, using a 2.5 x 15 Voyager balloon, we performed repeated dilatations within the LCX without success to restore flow throw the occluded stent.

As a result, the patient was left with an occluded LCX and had a complete lateral wall infarction. He remained hemodynamically stable and was subsequently discharged home. At 6-month follow-up, he was asymptomatic and had no further clinical events. His echocardiogram at 6 months demonstrated an ejection fraction of 55% with akinesis of the posterior wall.

Discussion. Aspiration thrombectomy during primary PCI has been shown to improve angiographic outcomes such as TIMI blush grade score.4 However, based on the results of a single-center study that found unexpectedly lower mortality with aspiration thrombectomy, there has been increasing enthusiasm for utilizing these devices during primary PCI.¹ However, there is a lack of reports of adverse events related to the device.

Our case demonstrates an example where an aspiration thrombectomy device brought a large amount of thrombus into the LMCA, a potentially life-threatening complication. This should be recognized as a potential complication in the left coronary system with a large thrombus burden. Important questions remain as to whether utilizing a larger diameter guide catheter (i.e., 7 Fr) can reduce the risk of thrombus shearing off the tip of a thrombectomy catheter as it is withdrawn. Another important issue is the optimal technique for aspiration; manufacturer instructions recommend stopping negative suction prior to catheter removal from the target vessel, but many interventionalists remove these devices on negative suction to avoid losing thrombus as one removes the device. In addition, other devices, such as balloons, have the potential to bring thrombus back into the left main and the comparative risk with thrombectomy devices is unknown.

The small trials of aspiration thrombectomy available are likely underpowered to examine adverse outcomes such as left main thrombus or left main dissection. Future large-scale registries and randomized trials will be better able to assess these risks.

Other potential complications of aspiration thrombectomy include stroke, air embolization, distal embolization of thrombus and vessel dissection and perforation. A meta-analysis of randomized trials³ has shown a trend toward possible increase in stroke (relative risk, 3.43; 95% confidence interval, 0.85–13.9), but the current trials are insufficiently powered to examine this question.

There are limited data with regard to use of aspiration thrombectomy during stent thrombosis. In a case series of 24 patients⁵ with definite stent thrombosis, aspiration thrombectomy was used successfully without any device-related complications. However, it is uncertain if the risk of bringing thrombus back into the left main during thrombectomy is greater during stent thrombosis than other STEMI due to typically large thrombus burden in stent thrombosis. Finally, in our case, intravascular ultrasound may have assisted in determining the etiology of acute stent thrombosis, but theoretically may also be associated with a risk of bringing thrombus back into the left main.

Interventional cardiologists need to recognize that aspirating thrombus back into the LMCA is a potentially life-threatening complication of aspiration thrombectomy during primary PCI in the left coronary system and should be prepared to deal with this complication.

References

1. Vlaar PJ, Svilaas T, van der Horst IC, et al. Cardiac death and reinfarction after 1 year in the Thrombus Aspiration during Percutaneous coronary intervention in Acute myocardial infarction Study (TAPAS): A 1-year follow-up study. Lancet 2008;371:1915–1920.

2. Burzotta F, De Vita M, Gu YL, et al. Clinical impact of thrombectomy in acute ST-elevation myocardial infarction: an individual patient-data pooled analysis of 11 trials. Eur Heart J 2009;30:2193–2203.

3. Bavry AA, Kumbhani DJ, Bhatt DL. Role of adjunctive thrombectomy and embolic protection devices in acute myocardial infarction: A comprehensive meta-analysis of randomized trials. Eur Heart J 2008;29:2989–3001.

4. Svilaas T, Vlaar PJ, van der Horst IC, et al. Thrombus aspiration during primary percutaneous coronary intervention. N Engl J Med 2008;358:557–567.

5. Lemesle G, Bouallal R, Sudre A, et al. Thrombus aspiration for the treatment of definite stent thrombosis. Arch Cardiovasc Dis 2010;103:33–38.

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From Hamilton Health Sciences, McMaster University, Hamilton, Ontario. The authors report no conflicts of interest regarding the content herein. Manuscript submitted April 20, 2010, provisional acceptance given May 18, 2010, final version accepted June 11, 2010. Address for correspondence: Dr. Sanjit S. Jolly, MD, MSc, Hamilton Health Sciences, McMaster University Medicine, DBCVSRI Building Rm C3-118, 237 Barton St. East, Hamilton General Hospital, Hamilton, Ontario, L8L 2X2, Canada. E-mail: jollyss@mcmaster.ca