Intravascular ultrasound to guide the management of intracoronary thrombus: a Case Report

Background

Patients with acute coronary syndromes (ACS) areincreasingly treated with an early invasive strategy. Duringpercutaneous coronary interventions (PCI) interventionalists have often to deal with thrombus-laden lesions innative coronary vessels. This poses the serious problem ofpreventing macroscopic and microscopic distal embolization [1]. There have been many recent advances in thisfield, and new tools are available for shielding the distalmicrovasculature, including occlusive systems and basketfilters. In the very emboli-prone saphenous vein graftsinterventions, for example, both techniques have beenassociated with favourable results [2,3].

In native vessels cost and efficacy [4] considerationsprompt a careful use of these devices, and a sensibleapproach could be selecting lesion and patients at highrisk of distal embolization. For example, preventing distalembolization is particularly important in young patientspresenting with their first coronary event with a largethrombotic burden [5,6].

Angiography alone is known to underestimate the risk ofdistal embolization: for example, only overt signs of massive thrombus burden are predictive of no-reflow in myocardial infarction patients treated with primary PCI [7].Intravascular ultrasound (IVUS) has the potential to

overcome many of the limitations of angiography, including lesion characterization and assessment of plaque rupture and thrombus [8-11], but its use is still restricted.We present a case of successful prevention of macroscopicdistal embolism in a young patient with ACS obtainedcombining IVUS and distal filter protection.

Case presentation

A 41-year-old lady presented with a short history of cardiac sounding chest pain. She was a smoker, had hypertension and had a strong family history of prematureischaemic heart disease. The ECG showed widespreadanterior T wave inversion. Conventional treatment wasstarted immediately for ACS including intravenousnitrates, low molecular weight heparin, aspirin and clopidogrel. The patient remained pain-free following admission and serial biochemistry demonstrated a rise incardiac troponin I to 24 mmol/l at 24 hours. There was noevidence of Q waves on the ECG and left ventricular function was normal on echocardiography.

Coronary angiography was undertaken four days afteradmission. This demonstrated mural thickening of theproximal left anterior descending (LAD) coronary arterywith a possible filling defect at the distal end of the lesionbut no evidence of coronary atherosclerosis elsewhere(Fig. 1B). Interrogation of the proximal LAD stenosis withIVUS (Galaxy II system; Atlantis 40 MHz Catheter, BostonScientific/Scimed, Inc., Maple Grove, Minnesota) showeda large intracoronary thrombus (Fig. 1C) adherent to amural atheromatous plaque starting at the ostium of LAD(Fig. 1A). The thrombus had a lobulated appearance withno evidence of internal blood flow or speckling. It contained echolucent areas indicating cavitation and consistent with ongoing thrombus organization. No evidence ofcomplete plaque rupture (intraplaque cavity communicating with the lumen) was seen.

Percutaneous coronary intervention was performed usingdistal filter protection with the EZ Filterwire (Boston Scientific, Natick, MA, USA). The GpIIb/IIIa antagonistAbciximab was administered. A 4.0 × 15 mm stent wasplaced directly with good final angiographic result (Fig.2B) and no evidence of macroscopic distal embolisation.Repeat IVUS confirmed good apposition of the stent andthe absence of residual thrombus (Fig. 2A&2C). Atretrieval, the Filterwire contained a small but significantamount of pink thrombotic material and yellowishplaque debris. Equivalent chest x-ray radiation dose(assuming a single posteroanterior projection chest x-rayis eight centi-Gray/cm2) was 380.

No further Troponin I elevation occurred; the patient wasdischarged home the next day, and remains asymptomaticat two months.

Discussion

Acute coronary syndromes with extensive thrombosis inthe absence of widespread coronary atheroma aredetected most frequently in young smokers [5,6].

The necessity of preventing distal embolic during PCI isbecoming increasing recognised, as traditional angioplasty may be associated with distal myocardial necrosis[1].

In our case, angiographic appearance was not suggestiveof either obstructive coronary disease or a high embolicrisk: none of the criteria set up by Yip et al [7] (cutoff pattern of occlusion, accumulated thrombus > 5 mm proximal to the occlusion, presence of floating thrombus,persistent dye stasis distal to the obstruction, referencelumen diameter of the culprit artery > or = 4 mm, andincomplete obstruction with presence of accumulatedthrombus more than three times the reference lumendiameter of culprit artery) was met, and the patient hadalready received prolonged antiplatelet and anticoagulant therapy.

However, we suspected the presence of a significantthrombotic mass, mainly on the clinical grounds of widespread ECG change and Troponin I elevation, and performed IVUS examination. The importance of the IVUSresults is clear: the visualization of a lobulated thrombus,loosely attached to an eroded, non-ruptured plaque,prompted us to use distal protection, which in turn mayhave prevented significant embolism.IVUS proved also useful in ensuring full coverage of thelesion, resolving the relation of the lesion with the LADostium, correctly sizing the stent, and ruling out thrombusor plaque prolapse through stent struts.

Conclusion

We present a case of successful management of an intracoronary thrombus, which was accomplished combiningIVUS data and a distal protection device.

IVUS proved invaluable in the diagnosis and treatment ofthis challenging case. We believe IVUS guidance should be considered for assessing thrombotic burden and embolism potential particularly in young patients with ACS when angiographic data are inconclusive.

Competing interests

The authors declare that they have no competing interests.

Authors' contributions

IP and AM have written the first draft of the manuscript.AB and IP have performed the coronary intervention. IP,AM, VA and AB participated in the design and coordination of the final manuscript. All authors have read andapproved the final manuscript.