An Image of Coronary Thrombus Mimicking Dissection Detected by Intravascular Ultrasound During Functional Evaluation of an Inter

During functional evaluation of an intermediate lesion in the circumflex coronary artery by pressure wire, an angiographically false image of long dissection extending from the left main coronary artery (LMCA) to the second obtuse marginal branch of the circumflex coronary artery and a large thrombus in the proximal parts of both the left anterior descending (LAD) coronary artery and the left circumflex (LCX) coronary artery were observed in a 68-year-old patient. Before proceeding directly with stenting, we performed an intravascular ultrasound (IVUS) examination to differentiate this image from thrombus without dissection. IVUS revealed a thrombus without dissection, which dissolved with anticoagulant therapy alone. The pressure wire and IVUS catheter can be used extensively for functional evaluation of intermediate coronary lesions. Operators may encounter various complications, such as coronary spasm, thrombus formation, coronary dissection, acute coronary closure and even acute myocardial infarction, during IVUS examination.1,2 Dissection of the LMCA can occur as a complication of cardiac catheterization and catheter-based intervention.3,4 Coronary dissection, which can cause acute coronary closure, should be diagnosed exactly and treated immediately with stenting. We present a patient who had an angiographic false image of dissection during functional evaluation of an intermediate lesion by pressure wire, and who subsequently underwent IVUS, showing only thrombus without dissection, and was then medically treated. Case Report. A 68-year-old man was admitted to our hospital because of exertional chest pain. Physical examination and electrocardiogram were normal. Stress electrocardiogram showed horizontal 2 mm ST-depression in inferolateral leads, which was accepted as positive. The patient underwent coronary angiography, revealing an intermediate lesion on the LCX (Figure 1). The diagnostic catheter was exchanged with a guiding catheter for functional evaluation of the intermediate lesion on the LCX. Activated coagulation time (ACT) was 90 seconds. Intravenous heparin was given in a dose of 10,000 U. A 0.014 in. pressure wire (RADI Medical Systems, Uppsala, Sweden) was advanced into the coronary artery past the lesion. Fractional flow reserve was measured as 0.82 after an intracoronary dose of 60 mg adenosine. Just before advancing the IVUS catheter (Atlantis SR, 40 MHz, Boston Scientific/Scimed, Inc., Fremont, California), we noticed an image of long dissection extending from the LMCA to the second obtuse marginal branch of the LCX artery and thrombi in the proximal parts of both the LAD and the LCX (Figure 2). This image was not noted on diagnostic angiography. We assumed this was a dissection, a probable complication of the pressure wire or the guiding catheter. We remeasured the ACT level (130 seconds) and proceeded with IVUS examination to clarify the diagnosis. IVUS examination of the LCX showed a smooth thrombus surrounding the IVUS catheter and extending to the second obtuse marginal branch of the LCX. IVUS led us to exclude dissection in the coronary artery (Figure 3). After exclusion of dissection, the wire and catheters were immediately removed. IVUS examination therefore prevented an unnecessary stenting procedure. The thrombus was successfully managed by intravenous heparin infusion and intravenous tirofiban infusion (0.5 mg/kg/min). The patient was taken to the coronary care unit. After 48 hours, he underwent a second coronary angiography, which showed no residual thrombus. He was discharged in good health and with no increase in CK-MB levels. Discussion. Calcification or atherosclerotic disease of the LMCA increases the risk of catheter-related coronary dissection. Also, anatomical distortion can complicate catheter engagement to the LMCA and prevent advancement of the wire to the LCX or LAD. The pressure wire, which is being used for functional evaluation of intermediate lesions and calculation of fractional flow reserve, may induce common complications, such as coronary spasm, coronary dissection, coronary closure and thrombus formation. IVUS, as a main component of morphologic analysis of intermediate lesions, can also cause coronary dissection and thrombus, followed by total occlusion. Identification of dissections is of great importance because of the risk of acute coronary closure. Moreover, the ability of coronary angiography to precisely detect dissection is very low. IVUS is a useful adjunct to angiography in selected patients for identification or exclusion of dissection and thrombus.4 Several studies confirm the superiority of angioscopy to IVUS in distinguishing between dissection and thrombus; however, angioscopy has not been widely used by interventionalists because of lack of steerability and suboptimal imaging of aorto-ostial lesions and proximal LAD and LCX lesions.5,6 We speculate that the thrombus overlying the proximal segments of both vessels without dissection may have occurred as a complication of the guiding catheter, but not as a complication of the wire and the IVUS catheter, because there were images of dissection and thrombus in the proximal parts of both the LAD and LCX, rather than only on the targeted LCX vessel. Therefore, the guide catheter could have partially blocked the coronary flow and caused stagnation and thrombus formation. Exclusion of dissection with IVUS examination can prevent additional angioplasty and stenting. This approach can avoid new dissections and unnecessary stenting, with which the risk of restenosis substantially increases. IVUS is a very useful adjunct to coronary angiography for identification or exclusion of dissection, and obviates unnecessary stenting in cases where coronary angiography is confusing.

1. Hausmann D, Erbel R, Alibelli-Chemarin MJ, et al. The safety of intravascular ultrasound: A multicenter survey of 2,207 examinations. Circulation 1995;91:623–630. 2. Ge J, Liu F, Kearney P, et al. Acute coronary artery closure following intracoronary ultrasound examination. Cathet Cardiovasc Diagn 1995;35:232–235. 3. Curtis MJ, Traboulsi M, Kundtson ML, et al. Left main coronary artery dissection during cardiac catheterization. Can J Cardiol 1992;8:725–728. 4. Mulvihill NT, Boccalatte M, Fajadet J, Marco J. Catheter-induced left main dissection: A treatment dilemma. Cathet Cardiovasc Intervent 2003;58:214–216. 5. Lee DY, Eigler N, Luo H, et al. Effect of intracoronary ultrasound imaging on clinical decision making. Am Heart J 1995;129:1084–1093. 6. Waxman S, Mittleman MA, Zarich SW, et al. Angioscopic assessment of coronary lesions underlying thrombus. Am J Cardiol 1997;79:1106–1109.