StentBoost Used to Guide Management of a Critical Ostial Right Coronary Artery Lesion

From the ^§Department of Interventional Cardiology, Onze Lieve Vrouwe Gasthuis, Amsterdam, the Netherlands. ^*Royal Jubilee Hospital, Victoria, B.C., Canada; ^£Kings College Hospital, London, United Kingdom. The authors report no conflicts of interest regarding the content herein. Manuscript submitted May 30, 2008, provisional acceptance given June 30, 2008, final version accepted October 21, 2008. Address for correspondence: Tycho Vuurmans, MD, PhD, Victoria Heart Institute, 200-1900 Richmond Avenue, V8R 4R2 Victoria, BC, Canada. E-mail: tychovuurmans@hotmail.com

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ABSTRACT: This report describes a case of a critical ostial lesion of a dominant right coronary artery (RCA) in a patient with poor left ventricular function due to a previous anterior infarction and documented late drug-eluting stent thrombosis of the RCA. The precise non-invasive determination of the proximal edge of a previously deployed stent by a new imaging technique, StentBoost, showed the lesion not only to be proximal to the stent in the uncovered ostium, but also restricted to the section outside the stent. This, together with the patient’s clinical factors, suggested that stent placement was the optimal treatment strategy.

J INVASIVE CARDIOL 2009;21:e19–e21

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StentBoost (Philips Medical Systems Nederland BV, Best, The Netherlands) is a new technology that uses motion-corrected fluoroscopic images to enhance coronary stent visualization to aid in the detection of inadequate stent expansion¹ and apposition to the vessel wall.² StentBoost shows a better correlation than quantitative coronary angiography for stent expansion when compared to intravascular ultrasound (IVUS),³ can diagnose poor stent deployment as a cause of restenosis,⁴ and can assess the deformation and the expansion of a stent deployed to treat a bifurcation lesion.⁵ The following case describes a patient who presented with a severe ostial right coronary artery (RCA) lesion. This RCA was a dominant vessel that supplied a large area of myocardium and its clinical importance was accentuated by the fact that a previous anterior infarction had left the patient with poor left ventricular function. The location of the lesion in relation to a previous stent was not clear and, as there were a number of possible pathologies to explain the severe ostial lesion such as edge stenosis, in-stent restenosis or thrombosis, this gave a number of different and sometimes mutually exclusive possible management strategies. IVUS would have been one method to investigate the lesion, but the procedure was complicated by the fact that engagement of the vessel led to severe symptoms. StentBoost proved to be an elegant solution to show the position of the stent and guide management. Case Report. A 50-year-old male was admitted to our center with stable angina (Canadian Cardiovascular Society grade III). He had had an extensive previous cardiac history, with an anterior wall infarction in 1991, followed by percutaneous coronary interventions (PCI) to the left anterior descending artery in 1991 and 1992. He had another anterior wall infarction in 1999 that was successfully treated with thrombolysis (as confirmed by an angiogram showing reperfusion performed in the acute phase). Elective PCI of a right posterolateral branch was been performed in 2001. In 2006, his angina had returned and he was found to have a long lesion involving the proximal- and mid-sections of the right coronary artery (RCA). This was treated with 3 stents: a 3.5 x 12 mm Taxus^® (Boston Scientific Corp., Natick, Massachusetts), a 3.5 x 32 mm Taxus and a 3.5 x 15 mm PRO-Kinetic (Buelach, Switzerland). Three days later, the patient had subacute stent thrombosis of the proximal RCA. Thrombectomy was performed with an Export™ aspiration catheter (Medtronic, Inc., Minneapolis, Minnesota)6 followed by balloon dilatation of the RCA with 3.5 and 4.0 mm balloons. He was treated post procedure with abciximab. The patient confirmed that he had been compliant with dual antiplatelet therapy previously. He was pain-free for 5 months after this procedure, but presented again with recognizable chest pain. A technetium sestamibi scan showed a dilated left ventricle (ejection fraction of 16% at rest and 12% after exertion), a persistent anterior perfusion defect and a large area of reversible posterolateral ischemia. Angiography at the referring hospital showed no significant stenoses in the left coronary artery, but the RCA had a severe ostial stenosis and engagement was complicated by pressure damping, chest pain and transient ST-segment elevation. He was transferred for further management to our hospital. Upon engagement of the RCA, there was damping of the pressure curve, ST-segment deviation on the monitor, and chest pain so the catheter was withdrawn. In order to minimize further ischemia, the catheter was preloaded with the angioplasty wire and the wire was passed as rapidly as possible after which the catheter was pulled back 1 cm. There was no chest pain or ST elevation with the wire in situ. The images showed a severe lesion at the ostium (Figure 1). It was felt that IVUS could be clinically hazardous, as it might compromise flow to a large, clinically important region of surviving myocardium. StentBoost was performed and showed a clear gap between the ostium and the beginning of the stent that was not visible on the maximally magnified standard image (Figure 2). The lesion was clearly restricted to the section of vessel just before the stent. Therefore, a 4.5 x 12 mm Taxus stent was deployed in the coronary ostium. StentBoost confirmed good deployment and overlap with the previous stent (Figure 3). Angiography showed a good result with thrombolysis in myocardial infarction (TIMI) 3 flow (Figure 4). The patient had an uncomplicated clinical course, with no increase in cardiac enzymes, and was discharged 8 days later. He had had no further problems at 4-month follow up. Discussion. StentBoost is a newly validated technology for visualizing stent deployment. This is a recently developed X-ray processing technique based on the currently available StentBoost system that enhances visualization of the stent in relation to the corresponding vessel lumen. To perform StentBoost, a single cine run is acquired, starting with approximately 2 seconds (30 frames) without contrast, followed by an additional 2–3 seconds of contrast injection. The image sequence is transferred automatically to an interventional Philips Allura Xper FD10 workstation which is part of the X-ray system. By superimposing motion-compensated image frames of the moving stent, a high-quality image of a deployed stent is generated. The application automatically matches the stent image with an image of the corresponding vessel lumen. The result is immediately visible in the examination room without any user interaction.² StentBoost has been described for use primarily in determining the adequacy of stent deployment. Conventionally, StentBoost is performed by leaving the balloon in situ and using the markers to superimpose the images, thereby stabilizing the angiographic section in between. We modified this by using the tip of the catheter and a clearly visible point along the stent trajectory. In this case, the RCA supplied a large viable section of myocardium in a patient whose left ventricular function was poor due to a previous anterior wall infarction. Engagement with the catheter by itself resulted in ischemia. There were a number of possible diagnoses for the severe proximal lesion, the first being that the native ostium had not been covered by the stent and that either the edge of the stent balloon or the balloon used for postdilatation performed 5 months previously for subacute stent thrombosis had resulted in stenosis. Stenosis is known to occur frequently after balloon angioplasty alone and usually occurs within 6 months after the procedure, often with subacute onset, as in our case. This can be treated by deployment of another stent (drug-eluting [DES] or bare-metal [BMS]). A second possibility was that the lesion was located within the previously deployed stent in the form of in-stent restenosis in the proximal DES, which could be treated by an additional DES. A third possibility was that there was thrombus present. This cannot be excluded based on the angiographic image alone and a recurrence of stent thrombosis was a possibility, particularly in view of the previous episode 6 months earlier. However, a thrombotic lesion often has an acute presentation and is more likely to occur at an earlier time point than 5 months (a reasonable time for edge stenosis). IVUS would have been optimal to evaluate these possibilities, as it would have shown the characteristics of the lesion and the exact relationship between the lesion and the RCA ostium. However, the IVUS probe itself might have risked prolonged ischemia and compromised cardiac function. In view of the fact that this was a clinically important myocardial territory, IVUS was contraindicated. Treatment options and stent choice depended on the position and type of lesion. First, aorto-ostial lesions would be appropriately treated with a DES in view of the high rates of restenosis after BMS implantation.7 Second, in-stent restenosis of a DES could be treated with an alternative DES. Third, treatment of thrombus would include thrombectomy and IVUS. Nonapposition could be treated by further dilatation and more aggressive anticoagulation. Additional use of a glycoprotein IIb/IIIa inhibitor and intensified, possibly “triple” antiplatelet therapy,⁸ could be considered (although there are only limited data on the prevention of late recurrent stent thrombosis).⁹ DES deployment has been shown to be safe in other thrombotic lesions such as acute myocardial infarction,^10–12 and could be justifiably considered in mixed lesions where there is thrombus on a restenotic lesion. The clear evidence obtained by using StentBoost showed the lesion to be located at, and restricted to, the previously unstented section of the vessel, i.e., the ostium. Furthermore, the circumstantial evidence of the patients’s presentation 5 months after the previous PCI, together with his subacute history, favored a diagnosis of edge stenosis. Therefore, the exact position of the edge of the stent in relation to the ostium shown by StentBoost was critical in our decision-making process and was not visible on the maximally magnified image acquired with the standard X-ray system. This noninvasive method of determining the location of the lesion in a section of vessel that had not previously been covered indicated that placement of another DES would be the most appropriate treatment.

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