ADVERTISEMENT
Revascularization of Thrombus-Laden Lesions in AMI —
The Burden on the Interventionalist
Throughout revascularization of coronary arteries and saphenous vein grafts in acute myocardial infarction (AMI) and acute coronary syndromes, the burden of a thrombus can be “felt” by interventionalists. You know that ominous “feeling” when angiography demonstrates a large size thrombus — a notorious marker of procedural complications. And, extensive literature clearly supports your concern,1–5 because visible thrombus poses imminent risk of flow impairment, distal embolization, “no reflow” phenomenon with micro-circular obstruction and infarct expansion. If treated inadequately, thrombus turns into an active, “angry” component causing further flow cessation and at times accounting for development of cardiogenic shock and even death. Can interventionalists discern the presence, quantify the size of a thrombus and proceed accordingly with a dedicated treatment strategy? The answer is controversial. Traditionally, it has been shown that angiography has a low sensitivity for detection of intracoronary thrombus, and it is likely that the true incidence of thrombus is underestimated.6,7 However, with recent improved imaging in the cath lab and heightened awareness to visible thrombus and its deleterious effects on outcome, interventionalists seem to have developed a more accurate appraisal of thrombus. When the accuracy of visual assessment of thrombus was validated by independent core lab QCA analysis, it has been convincingly demonstrated that interventionalists can precisely identify and differentiate between each level of TIMI thrombus grade and treat accordingly.8
The best method for the percutaneous undertaking of a large size thrombus in AMI is yet unknown and management strategies vary considerably. Limited treatment with only heparin is still in use due to severe underestimation of the thrombus hazard. In contrast, attempts at complete thrombus burden removal with mechanical devices appear to gain momentum. Unfortunately, many in the field still attempt to handle visible large size thrombus with balloon only, perhaps due to a lingering influence of early days (“When I face a large coronary thrombus I just beat it to death with the balloon,” was frequently heard from one of the field’s founders). Some continue to treat angiographic thrombus with the quite ineffective glycoprotein IIb/IIIa receptor antagonists,9,10 while others manage visible thrombus with unsubstantiated use of filter protection.11 Many then naively deploy a stent for thrombus displacement hoping that it will somehow end up squeezing the thrombus and associated debris selectively onto the vessel’s wall. In several high volume centers, mechanical thrombectomy devices are first in line, frequently in combination with direct coronary injections of low-dose thrombolytics.12 Regardless, the burden of the thrombi continues to be high and costly.
In this issue of the journal, Burzotta et al13 describe early experience of treating thrombus-laden lesions in AMI by applying an aspiration catheter and a distal protection device. The authors are to be commended for the concept and especially for avoiding the temptation to routinely use a thrombus removal device for all AMI lesions. They correctly centered their efforts on lesions with significant thrombus load. In contrast, a Rescue aspiration catheter was unjustifiably applied in a recent AMI study to all lesions regardless of visible thrombus.14 A similar mistaken strategy took place in the rheolytic thrombectomy AIMI study.
The revascularization technique of Burzotta et al incorporated aspiration first, then distal protection followed by stent implantation. The aspiration was done with a Diver CE catheter that was slowly advanced in aspiration mode along the culprit lesion. Once the syringe was full, the device was retracted and reintroduced up to six times. The aim was creation of a tunnel within the thrombus which would enable crossing for deployment of a distal protection filter. While utilization of aspiration devices is simple technically, in our experience they do not provide adequate removal of large size thrombus, especially multilayered, resistant clot. The frequent need to recross the target several times certainly adds to the risk of distal embolization. Moreover, from a technological standpoint, to ensure maximal efficiency, an aspiration catheter needs to provide multiple largesized holes that drain into a large extraction lumen. This is required to accommodate large thrombus content and its debris. Intriguingly, the present generation of aspiration catheters are designed to “forcefully” fit into a 6 Fr guiding catheter. Such small lumen diameter probably compromises the efficiency of the abovementioned holes. As for filter protection devices, the concept is attractive but their performance is questionable11; the receiving vessel requires a landing zone of no less than 3–4 cm, and deployment can be cumbersome. Furthermore, the revascu-larization method of Burzotta and associates required advancement of the protection filter across lesions that still contained residual thrombus — a drawback.
With these points in mind, a careful examination of the results as obtained by the investigators13 is warranted. Indeed, the operators achieved final TIMI 3 flow in 90% of the patients and a final myocardial blush grade 3 in half of the cases. However, the aspiration did not provide adequate thrombus removal in 40% ! This forced the operators to predilate with a balloon, thus displacing the residual clot and defying the intention of protection from thrombus debris. The improvement in TIMI flow after aspiration was modest at best: from 0.7 to 1.6. Arguably, better TIMI flow, myocardial blush, ST-resolution and corrected TIMI frame count could be achieved with direct thrombus aspiration/excision by mechanical thrombectomy devices. This was demonstrated in the X-Sizer thrombectomy XAMINE ST trial,15 in the ultraviolet excimer laser CARMEL multicenter study,8 and the Italian experience with rheolytic thrombectomy.16
The authors previously published the randomized study REMEDIA showing that Diver CE application in AMI results in better angiographic and EKG myocardial reperfusion rates as compared with those achieved by standard PCI.17 Specifically, higher thrombus score identified the patients with the greatest combined reperfusion benefit from thrombus aspiration. This important observation perfectly matches a main finding of the CARMEL study of excimer laser in AMI,8 whereby maximal laser gain was achieved in lesions that contained the heaviest thrombus burden. A logical conclusion can then be made, a visible thrombus calls for removal, however, thrombus removal devices should not be routinely used for lesions lacking significant thrombus burden.
Altogether, in PCI for AMI, the thrombus burden on lesions and the interventionalists alike necessitates pointed management. Most importantly, thrombus removal devices should be reserved only for thrombus-laden lesions.
References
1. Kalyanasundaram A, Blankenship J, Berger P, et al. Thrombus predicts ischemic complications during percutaneous coronary intervention in saphenous vein grafts: Results from TARGET [Do Tirofiban and Reopro give similar efficacy trial? Catheter Cardiovasc Intervent 2007:69:623–629.
2. Eguchi H, Ikeda H, Murohara T, et al. Endothelial injuries of coronary arteries distal to thrombotic sites: Role of adhesive interaction between endothelial Pselectin and leukocyte sialyl Lewis X. Circ Res 1999:84:525–535.
3. Henriques JP, Zijilstra F, Ottervanger JP, et al. Incidence and clinical significance of distal embolization during angioplasty for acute myocardial infarction. Eur Heart J 2002:23:1112–1117.
4. Lincoff AM,Topol EJ. Illusion of reperfusion: Does anyone achieve reperfusion during acute myocardial infarction? Circulation 1993:88:1361–1374.
5. White CJ. Angiographic predictors of adverse outcomes in the modern interventional era. J Am Coll Cardiol 2003:42:989–990.
6. den Hejer P, Foley DP, Esccaned J et al. Angioscopic versus angiographic detection of intimal dissection and intracoronary thrombus. J Am Coll Cardiol 1994:24:649–654.
7. Teirstein PS, Schatz RA, DeNardo SJ, et al. Angioscopic versus angiographic detection of thrombus during coronary interventional procedures. Am J Cardiol 1995:75:1083–1087.
8. Topaz O, Ebersole D, Das T, et al. Excimer laser angioplasty in acute myocardial infarction-the CARMEL multicenter study. Am J Cardiol 2004:93:694–701.
9. Topaz O. Ischemic coronary syndromes and SVG interventions-do 2b/3a inhibitors miss the target? Catheter Cardiovasc Intervent 2007:69:630–631.
10. Zhao XQ, Theroux P, Snappin SM, Sax FL. Intracoronary thrombus and platelet glycoprotein 2b/3a receprtor blockade with tirofiban in unstable angina or Q-wave myocardial infarction. Circulation 1999:100:1609–1615.
11. Stone GW, Webb J, Cox DA, et al. Distal microcirculatory protection during percutaneous coronary intervention in acute ST-segment elevation myocardial infarction: A randomized controlled trial. JAMA 2005:293:1063–1072.
12. Topaz O, Perin E, Jesse RL et al. Power thrombectomy in acute coronary syndromes. Angiology 2003;54;457–468.
13. Burzotta F, Trani C, Romagnoli E et al. Feasibility of sequential thrombus aspiration and filter distal protection in the management of very high thrombus burden lesions. J Invasive Cardiol 2007;19; 317–323.
14. Kaltoft A, Bottcher M, Nielsen SS, et al. Routine thrombectomy in percutaneous coronary intervention for acute ST-segment elevation myocardial infarction — A randomized controlled trial. Circulation 2006:114;40–47.
15. Lefevre T, Garcia E, Reimers B, et al. X-Sizer for thrombectomy in acute myocardial infarction improves ST-segment resolution. J Am Coll Cardiol 2005;46;246–252.
16. Antoniucci D, Valenti R, Migliorini A, et al. Comparison of rheolytic thrombectomy before direct infarct artery stenting versus direct stenting alone in patients undergoing percutaneous coronary intervention for acute myocardial infarction. Am J Cardiol 2004:93:1033–1035.
17. Burzotta F, Trani C, Romagnoli E, et al. Manual thrombus aspiration improves myocardial perfusion: The randomized evaluation of the effect of mechanical reduction of distal embolization by thrombus-aspiration in primary and rescue angioplasty [REMEDIA] trial. J Am Coll Cardiol 2005:46:371–376.
