Which Is The True Channel?

Case report. A 70-year-old woman with a history of smoking, hypertension and hyperlipidemia was referred for evaluation of exertional angina that had developed over the preceding 6 months. Thirteen years earlier, she had undergone balloon angioplasty of the mid-RCA following acute myocardial infarction. That procedure resulted in an acceptable final residual stenosis (estimated to be 25% by visual severity), but was notable for the creation of a longitudinal dissection at the angioplasty site. Current diagnostic cardiac catheterization documented the presence of a disrupted-looking significant stenosis of the proximal RCA, in addition to two parallel stenotic-appearing channels in the mid RCA (Figure 1). There were no other significant lesions in the coronary tree, and the left ventricular function was within normal limits. A decision was therefore made to treat the RCA lesions with percutaneous coronary intervention (PCI). Patient management. Separate coronary wires were successfully inserted into each channel without any difficulty. Figure 2A shows the successful insertion of a first wire into the “posterior” channel. Figure 2B shows the presence of a second wire within the “anterior” channel. Figure 2C shows both coronary wires across the parallel channels of the mid-RCA. The proximal RCA lesion was pre-dilated with a 2.25–15 Maverick balloon (SCIMED, Maple Grove, Minnesota), then successfully stented with a 3.0–18 S7 stent (Medtronic AVE, Santa Rosa, California). We then performed intravascular ultrasound (IVUS) of the mid-RCA while using an Atlantis SR-PRO system (SCIMED). IVUS was sequentially performed in each of the channels and confirmed the presence of two separate lumens with proximal and distal communications. Figure 3 shows the presence of the IVUS catheter within the “posterior” channel. Given the severity of the lesion surrounding that channel, the walls of the lumen abut against the catheter. The “posterior” channel was identified as the true lumen, whereas the other (“anterior”) channel appeared to be a neo-vessel without intimal or medial layers, presumably stemming from the previous angioplasty dissection. The stenosis around the true channel was subsequently treated with stent implantation, using 2.75–20 Express (SCIMED) and S660 2.75–24 (Medtronic AVE) stents. Stenting resulted in an excellent angiographic result and the (angiographic) disappearance of the parallel neo-channel (Figure 4). The patient was discharged home 24 hours following the procedure without complication and remains free of anginal symptoms since PCI 6 months ago. This case documents the unusual appearance of a healed old dissection plane as a pseudo-lumen(analogous to a pseudoaneurysm), emphasizing the need for careful intravascular evaluation to determine the true channel and thus potentially avoid catastrophic rupture of a coronary vessel during coronary intervention. How Would You Treat This Patient? Punit Goel, MD, FACC, and Kul Aggarwal, MD, MRCP (UK), FACC University of Missouri-Columbia and Harry S. Truman Veterans Hospital Columbia, Missouri Coronary arterial dissection is a common consequence of balloon angioplasty. Mechanisms by which balloon angioplasty improves coronary blood flow past stenotic lesions include medial dissection, plaque fracture and intimal splitting. In the pre-stenting era, intravascular ultrasound (IVUS) and angioscopic studies have reported the incidence of dissections to be as high as 60–80%.^1,2 The National Heart, Lung and Blood Institute (NHLBI) has classified dissection types as: A. minimal radiolucency, not persistent B. “double lumen,” not persistent C. extra-luminal cap with persistence of contrast dye after the lumen has cleared D. spiral dissection E. persistent new filling defect F. dissection resulting in impaired flow/total occlusion. Complex dissections (type C through F) contain deep medial tears and are most powerful predictors of acute closure. Type A or B dissections are common after balloon angioplasty and usually associated with benign outcomes with acute closure rate of 3%. In contrast, complex dissections were associated with 5- to 10-fold higher risk for death/myocardial infarctions/emergent bypass surgery before the availability of the stents.³ In the current stent era, acute closure secondary to dissection following balloon angioplasty is extremely unusual, however, edge dissection following stenting may predispose to stent thrombosis. A vast majority of dissections from balloon angioplasty not associated with acute complications disappear with time⁴ and dissections per se have no impact on restenosis.⁵ In the case under discussion, the authors must be commended for describing a novel use of IVUS to identify the true lumen of chronic longitudinal dissection from angioplasty performed thirteen years earlier. Since there was an additional significant lesion in the proximal RCA, it is difficult to ascribe patient’s symptoms to the chronic dissection although in author’s opinion the IVUS suggested it to be significant. We would have used an alternate approach in this case. We would have assessed the hemodynamic significance of this dissection with measurement of fractional flow reserve (FFR) in the distal vasculature following the proximal lesion stenting. The RADI pressure wire is much smaller in caliber than the IVUS catheter and would have given an accurate assessment of physiologic/hemodynamic significance of the lesion rather than just the anatomic imaging. Additionally, it would have provided an assessment of the composite effect of flow down both channels which would have been a more accurate representation of conditions in this case. The 2 channels of chronic dissection would probably have been sufficient to provide distal flow with normal FFR thereby obviating the need for mid RCA intervention. Of course, this approach would not have allowed for distinction between the true and false lumens in case both channels did turn out to be significantly obstructive. However, it could be argued that stenting either channel in this case with chronic dissection would have resulted in a satisfactory outcome since each channel was connected at the proximal and distal ends to the true lumen. David Ramsdale, MD and Shahid Aziz, MRCP The Cardiothoracic Centre Liverpool, United Kingdom This is an interesting case dealing with the management of a healed chronic dissection resulting in two parallel stenotic channels in the mid-right coronary artery. Guidewires are passed down both the anterior and posterior channels with a view to coronary stenting. The appearance of two channels angiographically may be formed by division of the true lumen into two, with both lumens surrounded by intima and media. In this situation, either channel may be used for stent implantation. However, a similar appearance may be formed by a dissection flap separating the true lumen from the false lumen, analogous to that of a chronic aortic dissection. In this case, it would be important to identify the true lumen to avoid the risk of vessel perforation and dissection by stenting in the false channel. Angiographically, it is impossible to distinguish between these two possibilities and we would agree with the decision to perform intravascular ultrasound. This confirmed that the anterior channel was the false lumen, located in the mid-third of the vessel and devoid of any intima or media. By correctly defining the anatomy, an excellent final angiographic result was obtained. Rajbir S. Sangha, MB, ChB and Peter Y.M. Hui, MD, FACC, FSCAI California Pacific Medical Center San Francisco, California The authors describe in their case report the successful management of a chronic right coronary artery dissection, which had occurred during a mid–right coronary artery angioplasty 13 months earlier. Intravascular ultrasound (IVUS) was used to demonstrate the appearance of both true and false lumens, allowing subsequent stenting of the true lumen to obliterate the false. IVUS has provided us with a better understanding of luminal pathology and the often discrepant appearance of vessels when imaged by contrast angiography. Use of ultrasound imaging provides an appreciation of the cross sectional appearance of the target vessel. Studies have demonstrated the utility of this mode of imaging in guiding accurate vessel sizing and gaining adequate target vessel apposition of the delivered stent.¹ IVUS is generally considered a low-risk procedure, however, there is morbidity associated with the introduction of the ultrasound catheter. Potential complications include coronary spasm, acute occlusion, dissection and/or thrombosis.² Although spasm is treated easily with intravascular nitroglycerin, more severe complications can occur in up to 3% of patients. As a result of such risks, it is unusual to perform IVUS in vessels where the luminal diameter is less than 1.5 mm.³ The authors provide angiographic pictures to illustrate their case. On the basis of the location and orientation of the right coronary artery (RCA) in the RAO projection depicted, one would anticipate that the true lumen was present posteriorly and the false lumen, more anteriorly. The posterior lumen also appears angiographically more consistent with the expected course of the true right coronary artery. Placing a single wire into the perceived true posterior lumen and subsequent demonstration of intima by intravascular ultrasound could have provided sufficient information to allow safe delivery and expansion of a stent into this lumen to obliterate the false channel. Using such an approach may have decreased any potential risk of introducing an intravascular ultrasound catheter into the anterior pseudo-vessel. This case report demonstrates the utility of IVUS in providing information that is not available from vessel angiography and emphasizes that IVUS can allow a safer assessment of an intended intervention by providing luminal information that is not easily available by other means in the catheterization laboratory.

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