Side-Strut Stenting Technique for the Treatment of Aorto-Ostial In-Stent Restenosis and Deformed Stent Struts

Percutaneous coronary interventions of aorto-ostial lesions, de novo or restenotic, are technically difficult and associated with a higher risk of procedural complications and poor long-term outcome.^1–4 To reduce elastic recoil and improve long-term patency, coronary stenting is routinely employed for aorto-ostial lesions and accomplished by placing a stent across the coronary ostium with the proximal stent segment protruding into the aorta to allow complete lesion coverage. Repeat intervention on an aorto-ostial stent for the treatment of in-stent restenosis poses unique challenges with regard to catheter engagement,⁵ guidewire placement6 and device usage.^7,8 In this report, we describe a method for angioplasty and stenting for a diffuse aorto-ostial in-stent restenosis associated with deformed stent struts. Case Report. A 56-year-old female initially presented with an acute coronary syndrome characterized by electrocardiographic evidence of myocardial ischemia and elevated biochemical markers. Coronary angiography revealed nonobstructive disease in the left coronary system and a 95% stenosis at the ostium of the right coronary artery that did not change with administration of intracoronary nitroglycerin (Figure 1A). Successful balloon angioplasty was performed followed by placement of a 3.0 x 13 mm Penta™ stent (Guidant Corporation, Indianapolis, Indiana), with its proximal edge protruding a few millimeters into the aorta, producing an excellent angiographic result (Figure 1B). The patient returned 8 months after the index procedure with symptoms of exertional angina. Repeat coronary angiography demonstrated diffuse in-stent restenosis of the aorto-ostial stent in the right coronary artery (Figure 2A). Repeat angioplasty and stenting, with placement of a drug-eluting stent was planned to treat the in-stent restenosis. Despite attempts with multiple guiding catheters and guidewires, the protruding stent could not be engaged in a coaxial fashion, suggesting deformation of the intra-aortic segment of stent struts. After failing to achieve coaxial guiding catheter alignment, we placed a 6 Fr Amplatz right (AR1) guide on top of the protruding stent segment and advanced a Whisper^® guidewire (Guidant) to the distal right coronary artery through the struts of the aorto-ostial stent. A 1.5 x 14 mm Maestro balloon (Abbott Laboratories, Abbott Park, *Illinois) was used to displace and widen the stent struts. This was followed by consecutive balloon dilatations using 2.0 x 14 mm, 2.5 x 14 mm, 3.0 x 14 mm and a 3.5 x 14 mm Maestro balloons inflated up to 18 atmospheres to widely open the stent cell and place a second stent. A 3.0 x 16 mm Taxus™ stent (Boston Scientific, Natick, Massachusetts) was successfully advanced through the widened stent cell and deployed at 16 atmospheres with 1–2 millimeters of the proximal stent segment protruding into the aorta for complete coverage of right coronary artery ostium. The fully-expanded Taxus stent displaced the intra-aortic segment of the previously placed stent inferiorly and created a new entry site into the artery, with excellent angiographic outcome (Figure 2B). Follow-up angiography performed at 6 months showed only mild recurrent in-stent restenosis (Figure 2C), with the patient remaining asymptomatic at 1-year clinical follow up. Discussion. Percutaneous coronary intervention of aorto-ostial coronary lesions is confronted by unique technical challenges not offered by other lesion subtypes.⁴ These include poor guiding catheter support, difficult stent placement and incomplete stent expansion. These challenges are further enhanced during repeat interventions by poor visualization of the intra-aortic component of stent struts, noncoaxial guiding catheter engagement⁵ and difficulty in placing the guidewire in the true stent lumen.⁶ Furthermore, causal attempts at engaging the protruded stent and coronary ostium may deform the stent struts, making further coaxial guiding catheter engagement impossible. Stenting for de novo aorto-ostial coronary lesions is recommended to prevent strong elastic recoil inherent to these lesions and to reduce the risk of restenosis, but precise stent placement is hampered by a lack of guiding catheter support and poor visualization during nonselective angiography. Despite these limitations, it is imperative that a stent be placed across the coronary ostium with only 1–2 mm of the proximal stent segment protruding into the aorta to allow complete lesion coverage and minimizes the risk of stent deformation during subsequent procedures. Similarly, when encountering a previously placed aorto-ostial stent, cautious catheter manipulation is essential to establish coaxial guiding catheter alignment without deforming the protruded stent struts. Although a right Judkins (JR 4) catheter can be used for coaxial stent engagement in many cases, if unsuccessful, further attempts with a horizontal tip (Hockey Stick, Williams, Amplatz right) or a LIMA guide may be effective. A buddy guidewire⁵ can also be used to improve guiding catheter alignment with the stent in difficult situations. Placement of a guidewire in the true lumen of the stent is often not difficult after coaxial guiding catheter engagement, but intricate guidewire techniques may be required if the protruded stent segment in the aorta is longer than a few millimeters. A Wiggle guidewire (Guidant) can be helpful in difficult-to-cross stents, and is more likely to stay in the true stent lumen as compared to regular-tip guidewires. Intravascular ultrasound can be used to confirm the intraluminal placement of the guidewire, but is technically challenging and may promote stent strut deformation if the guidewire was initially advanced across stent struts. As evident from the present case, deformation of the protruded stent struts may not be apparent radiographically, and failure to achieve coaxial guiding catheter alignment, despite cautious attempts with multiple guiding catheters and the inability to advance the guidewire through the true stent lumen, may be the only signs of occult stent strut deformity. We overcame these difficulties by placing the guiding catheter on top of the protruded stent and advanced a hydrophilic guidewire though the struts of the intra-aortic stent segment (Figures 3A and 3B). Serial balloon dilatations with sequentially larger, low-profile balloons were performed to widen the stent cell opening and dilate the restenotic lesion. This facilitated the passage and placement of a second Taxus stent across the lesion through the widened stent cell opening. Although angioplasty through stent struts has been reported for dilatation of aoto-ostial in-stent restenosis,⁹ to our knowledge, this is the first report of a “side-strut stenting” technique for aorto-ostial in-stent restenosis. Side-strut stenting represents a modification of the “Culotte” technique,10 and displaces the intra-aortic segment of the previously placed stent laterally, thus creating a new entry site into the coronary artery (Figure 3C). In the present case, we performed side-strut stenting in a Penta stent which features an open-cell design that may be more suitable for this technique, as the stent architecture permits unimpeded widening of the stent cells for up to 4 mm without damaging stent struts. Stents with a closed-cell design, on the other hand, permit limited expansion of the stent cell, and the passage of larger balloons and stents may cause fracture of stent struts. Despite the favorable architecture of one stent type for this intervention strategy, we believe that it can applied to both open- and closed-cell stent designs with equivalent success, as fractured struts are compressed and displaced laterally with the placement of the second stent without affecting blood flow through the stent lumen. Adequate dilatation of the indwelling stent cell opening using larger balloons is an important prerequisite of the successful side-strut stenting technique to avoid resistance and difficulty in advancing the second stent. Although careful cannulation of the aorto-ostial stent during repeat coronary angiography and placement of the guidewire and stent through the true stent lumen during repeat intervention remain the ideal approach for aorto-ostial in-stent restenosis, this report shows the feasibility of the side-strut stenting technique with good long-term outcomes in cases where stent strut deformation prevents coaxial guiding catheter engagement and passage of a balloon or a stent through the true lumen.

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