Negative Remodeling at the Ostium of the Left Circumflex Artery

Recently, lower restenosis rates have been demonstrated by directional coronary atherectomy (DCA) followed by stenting compared to stenting alone.1 This strategy may be suitable for ostial lesions, which are associated with a high risk of acute complications and a high restenosis rate.2 Because DCA removes atherosclerotic plaque and elastic elements, which are abundant at the ostium, DCA followed by stenting may result in a larger final lumen size and less incidence of sidebranch compromise due to plaque shift compared to stenting alone.1,3 However, this strategy has a risk of coronary perforation or subsequent aneurysm formation, especially when applied to a lesion with negative remodeling (vessel shrinkage).4,5 This case report describes an ostial lesion with negative remodeling. Case Report. A 57-year-old male who had shortness of breath for 1 year was referred for coronary angiography, which revealed a 60% stenosis at the ostium of the left circumflex artery (LCX) (Figure 1). There was no significant stenosis in the left anterior descending coronary artery (LAD) or the right coronary artery. Left ventricular function was normal. The patient was referred for coronary angioplasty. We planned to evaluate the lesion using intravascular ultrasound (IVUS) and to then perform directional atherectomy followed by stenting if the lesion was significant by IVUS imaging. A 0.014´´ Balance guidewire (Guidant Corporation, Temecula, California) was advanced into the distal LCX. After intracoronary injection of 200 µg nitroglycerin, IVUS imaging was performed from the proximal LCX to the left main using a 30 MHz, 3.2 French UltraCross catheter (Boston Scientific/Scimed, Inc., Maple Grove, Minnesota). IVUS images revealed no significant stenosis and negative remodeling at the ostium of the LCX (Figures 2A and 2B). Fractional flow reserve using the PressureWire (RADI Medical Systems AB, Uppsala, Sweden) was evaluated and demonstrated to be 0.95 after intracoronary injection of 36 µg adenosine. The lesion did not undergo intervention. Discussion. In this case, DCA might have resulted in coronary perforation or subsequent aneurysm formation without evaluating the lesion by IVUS imaging. Conventional balloon angioplasty for ostial lesions is limited by a high risk of complications, suboptimal dilatation due to elastic recoil and a high restenosis rate.2 DCA is suitable for ostial lesions. However, subanalysis of the Coronary Angioplasty Versus Excisional Atherectomy Trial (CAVEAT), which compared conventional balloon angioplasty to DCA in ostial LAD lesions, showed no difference in angiographic restenosis between the two groups.6 Previous studies7,8 demonstrated a high procedural success rate and an acceptable late clinical outcome of stenting in ostial lesions. However, stenting at the ostium of a bifurcation has a risk of sidebranch compromise due to plaque shift.7–10 If the sidebranch compromised is small, this condition may be well tolerated without clinical events. However, occlusion or narrowing of a large sidebranch supplying a substantial mass of myocardium may not be well tolerated and should be avoided.3,8 Recently, lower restenosis rates were demonstrated with DCA followed by stenting compared to stenting alone.1 This strategy may be suitable for ostial lesions. Because DCA removes atherosclerotic plaque and abundant elastic elements at the ostium, larger final lumen size and less incidence of sidebranch compromise due to plaque shift may be achieved by DCA followed by stenting compared to stenting alone.1,3 Positive (adaptive) remodeling of the wall of diseased arterial segments occurs to compensate for the accumulation of atherosclerotic plaque.11 The compensatory vessel enlargement delays luminal compromise until atherosclerotic plaque occupies 40% of the internal elastic lamina area.11 However, compensatory enlargement does not always occur. Previous studies12–17 demonstrated inadequate remodeling of the diseased vessels, some of which underwent vessel shrinkage (negative remodeling). The incidence of negative remodeling has been shown to be 15–36%.12–17 Fibrocalcific plaques13–15 and smoking12,13 were demonstrated to be predictors of negative remodeling. However, there is little information about the incidence of negative remodeling in ostial lesions because previous studies13–16 excluded these lesions due to the lack of an appropriate proximal reference site for comparison. In this case, there is a possibility that the stenosis at the ostium was temporarily observed due to coronary vasospasm. However, intracoronary injections of nitroglycerin were used to prevent vasospasm and no angiographic changes were observed before or after the IVUS imaging procedure. The mechanisms leading to inadequate remodeling are unclear. Several possible explanations have been postulated.14,16 The fibrocalcific elements (especially superficial calcification), which are often observed in lesions with inadequate remodeling, may have limited the adaptive response to plaque accumulation.2 Maturing of the atherosclerotic plaque with a reduction in lipid content, an increase in fibrosis and calcification, and apoptosis may result in reduction of the atherosclerotic plaque and a subsequent decrease in vessel area.3 There may be local impairment of endothelial vasomotor function that induces compensatory enlargement of the vessel.4 An inflammatory process or change in the adventitial or vessel wall tissue composition might result in inadequate remodeling. Contrast angiography has been the standard for evaluating the extent of coronary artery disease. However, this technique is unable to demonstrate plaque burden and vessel remodeling at the lesion site. IVUS imaging provides unique, detailed cross-sectional images of the arterial wall not previously obtainable in vivo by any other technique and is more sensitive than angiography in detecting atherosclerosis.18 The cross-sectional perspective of IVUS appears to be ideally suited for precision measurements of luminal diameter and cross-sectional area, especially in complex lesions such as ostial and bifurcation lesions.19 IVUS can also provide the information about plaque burden and vessel remodeling. IVUS guidance is essential to perform DCA followed by stenting in ostial lesions.1 IVUS imaging can provide precision measurements of luminal diameter and cross-sectional area and reveal the lesions with negative remodeling where DCA might result in coronary perforation and subsequent aneurysm formation.2,4,5 IVUS is useful to evaluate the result after DCA and stenting. A previous study showed that in order to obtain a beneficial effect from debulking in terms of a lower restenosis rate, no more than 60% of residual plaque needs to be present.1 Because of high restenosis rates in ostial lesions, it is crucial to maximize the final lumen size by IVUS guidance.3 DCA is not applied to ablate heavily calcified plaque. IVUS often demonstrates heavily calcified lesions that could not be appreciated by coronary angiography.20 Liberal use of IVUS is warranted to treat ostial lesions, especially when DCA might be used. IVUS guidance minimizes the risk of complications and maximizes final lumen size.

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