The Ostial Pro Stent Positioning System:Perfecting Aorto-Ostial Stent Placement

Disclosure: Dr. Saltiel and Dr. Fischell hold a financial interest in Ostial Solutions, Inc., which owns the Ostial Pro.

Introduction
As the field of interventional cardiology has continued to progress, the need for lesion-specific devices for complex and higher risk lesions has increased. Unfortunately, there has been relatively little improvement in devices to assist in the treatment of most complex lesion subtypes (e.g., CTOs, bifurcation lesions, etc.). However, a recently approved device shows promise to improve the results, and simplify the treatment of aorto-ostial lesions.
Aorto-ostial lesions are technically more complicated due to the marked elastic recoil and heavy calcification associated with these lesions.¹ As such, the standard treatment for these lesions involves compulsory stent implantation (occasionally with adjunctive debulking or cutting balloon angioplasty).^2-5 However, stenting of the ostium poses additional challenges since extremely precise positioning is essential, and the use of standard angiographic landmarks is often misleading.6 Misplacement of the stent by even a few millimeters can result in adverse outcomes.⁶ Moreover, it is well documented that stented aorto-ostial lesions demonstrate worse long-term results as compared to lesions elsewhere in the arterial tree.^2,4,5,7 This is likely due in part to misplacement of the stent, in not covering the true ostium of the vessel.

In order to improve the accuracy of stent placement, several modifications of standard techniques have been proposed, but none have been widely applied.^8,9 The Ostial Pro^™ (Ostial Solutions, Inc., Kalamazoo, MI) is a new device designed specifically to aid in the precise placement of stents in aorto-ostial locations. The device consists of a nitinol wire with a distal cylinder which is slit, permitting removal of the device without compromising wire position. The device can be front or back-loaded. There are four thin, flexible, self-expanding legs arising from this cylindrical portion. Gold markers are located on the tip of the legs to allow for fluoroscopic visualization (Figure 1). After the ostial lesion has been wired and with the stent delivery system distal to the lesion, the Ostial Pro is advanced inside the guiding catheter over the stent delivery system until the gold plated legs “pop out” just beyond the tip of the guiding catheter. The guiding catheter is advanced until the legs abut the aortic wall surrounding the ostial lesion. This serves to not only mark the true plane of the ostium, but also prevents the guide from entering into the vessel and stabilizes the guide during the intervention. The stent delivery system is then simply withdrawn to a position just distal to the guide tip. Contrast injection at this point helps to even better define the precise position of the proximal stent struts. Once the exact position is confirmed, the stent is deployed at that location. The Ostial Pro device is then removed from the guiding catheter. A second inflation to “flare” the proximal stent struts at the true ostium is performed with the balloon withdrawn another 2-3 mm. This has been demonstrated by intravascular ultrasound (IVUS) imaging to result in highly accurate positioning of the stent, to within 0.1-0.2 mm of the true ostium.
We report two cases of right coronary ostial stenting using the Ostial Pro stent positioning system. The device can also be utilized in a similar fashion for stenting of saphenous vein grafts, left main, renal artery, as well as other anatomically suitable aorto-ostial stenoses.

Case 1. A 67-year-old male with history of remote myocardial infarction with stenting of the left circumflex artery, hypertension, and hyperlipidemia presented with exertional angina. Nuclear stress imaging demonstrated the presence of inferior ischemia and cardiac catheterization was recommended. Coronary angiography revealed a widely patent stent in the circumflex, a moderate stenosis of the proximal anterior descending artery, and a high grade stenosis at the ostium of the right coronary artery (RCA) with significant dampening of the pressure wave form and reduced backflow of dye into the aorta (Figure 2, left panel). Percutaneous intervention of this lesion was recommended.
Since angiography did not demonstrate significant calcification, direct stenting was planned. The Ostial Pro was back-loaded into a 6 French Judkins 4 right guiding catheter with side holes. A 0.035” J-guidewire was passed through the Ostial Pro and the guide was advanced, flushed, and engaged into the RCA ostium in a standard fashion. The coronary guidewire and a 3.5 mm x 18 mm length Cypher (Cordis Corporation, Miami Lakes, FL) drug-eluting stent were advanced in the guide, through the Ostial Pro (still inside the guiding catheter), and past the ostial lesion. The guide was withdrawn slightly and the Ostial Pro was advanced beyond the distal tip of the guiding catheter. The legs of the Ostial Pro expanded and the guiding catheter was advanced slightly until the legs could be felt to come in contact with the wall of the aorta. This was confirmed visually by the action of the legs bending and flattening. This indicated appropriate positioning of the Ostial Pro, which was confirmed with contrast injections. The location of the ostium, as suggested by the pre-intervention angiogram, was actually several millimeters distal to the true ostium, which was clearly demarcated with the use of the Ostial Pro. The stent delivery system was then withdrawn to a position just distal to the guide tip (Figure 2, center panel). The presence of the Ostial Pro eliminated the need for further manipulation of the guide during stent positioning and deployment (often a tricky maneuver when positioning a stent at the ostium). Positioning was again confirmed by contrast injections and the stent was inflated at the position to 16 atms. The Ostial Pro device was withdrawn from the guiding catheter (leaving the coronary guide wire and stent balloon in place). Once the device was removed, the stent delivery balloon was withdrawn partially into the aorta and the balloon was again inflated to 16 atms to flare the proximal portion of the stent. The stent delivery system was withdrawn and the RCA re-cannulated. Radiographic and intravascular ultrasound (IVUS) imaging (iLab System, Boston Scientific, Natick, MA) were performed indicating good stent apposition and placement of the stent exactly at the true ostium of the vessel (Figure 2, right panel and Figure 3, upper panel). The patient has had no further angina.

Case 2. A 78-year-old male with a long previous history of smoking, obstructive pulmonary disease, laryngeal carcinoma with previous tracheotomy, and peptic ulcer disease with gastrointestinal bleeding presented with an acute coronary syndrome. After medical stabilization with aspirin, a GP IIb/IIIa inhibitor, and heparin, the patient was brought to the cardiac cath lab. Coronary angiography revealed moderate diffuse disease of his anterior descending artery and an anomalous circumflex arising from the proximal portion of the RCA. The circumflex was sub-totally occluded in its proximal portion. In addition, the RCA itself had an anomalous origin arising inferiorly in the right coronary cusp and with a downward take off. There was a high grade, calcified ostial stenosis of the RCA (Figure 4, left panel). Intervention was performed on the lesion in the proximal portion of the anomalous circumflex with the placement of a 2.75/15 mm Vision stent (Abbott Vascular, Redwood City, CA). Due to the anomalous take off of the RCA and significant guiding catheter instability, the precise location of the ostium was difficult to ascertain and no attempt to intervene on this lesion was undertaken. The patient did well and returned to the cath lab several days later for intervention of the RCA with the assistance of the Ostial Pro.

With the Ostial Pro preloaded into a 6 French modified right guiding catheter with side holes, the guide was brought to the ascending aorta and with some difficulty, the RCA was cannulated. A coronary guidewire was passed distally into the vessel. Passage of the stent delivery catheter beyond the ostial stenosis resulted in disengagement of the guiding catheter. The Ostial Pro was advanced distal to the tip of the guiding catheter and the catheter was advanced until the legs of the Ostial Pro flexed as the came in contact with the aortic wall (Figure 4, center panel and inset). With the Ostial Pro in position, there was a marked improvement in both the stability of the guide and its co-axial alignment with the downward going artery. The stent delivery catheter was withdrawn until the proximal marker was just distal to the tip of the guide. After dye injections confirmed proper positioning, the 3.5/15 mm Vision stent was deployed without difficulty. The Ostial Pro was removed from the guiding catheter, the balloon was withdrawn partially into the aorta, and final high pressure inflation was performed to flair the proximal portion of the stent. As in Case 1, radiographic and IVUS imaging were performed, indicating placement of the stent exactly at the true ostium of the vessel (Figure 4, right panel and Figure 3, lower panel). The patient’s post procedure recuperation was unremarkable.

Discussion
These cases illustrate several of the technical challenges encountered during stent-based intervention in aorto-ostial lesions. These include occlusion of the ostium by the guiding catheter, excessive guide manipulation during stent positioning (often resulting in instability of the guide catheter position), lack of co-axial alignment of the guiding catheter and most importantly, misjudgment of the true ostial location. These issues are largely overcome with the use of the Ostial Pro, and the resulting stent position appears to be predictable and precise. In short, the Ostial Pro achieves the most important features of a lesion-specific device; it makes stenting of aorto-ostial lesions not only easier and faster, but also better and safer.

This article received double-blind peer review from members of the Cath Lab Digest Editorial Board.