Perfection of Precise Ostial Stent Placement

Abstract: Ostial lesions, including aorta-ostial lesions and Medina 001 bifurcation lesions, are known to create difficulty in precise stent placement. There are many techniques used to help in precise ostial stent placement; these include using multiple angiographic views to assist in placement, the use of the Ostial Pro device, the aorta flowing wire technique, Szabo (anchor-wire) techniques, the T-stent and small protrusion (TAP) technique, the cross-over 1-stent technique, and new dedicated ostial stents. In this review, we summarize these different techniques and show that there is no universal technique that allows for perfect ostial stent placement.

J INVASIVE CARDIOL 2012;24(7):354-358

Key words: ostial stent, PCI, Szabo technique

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Coronary bifurcation lesions occur commonly and are currently widely treated by many interventional cardiologists. Randomized trials have suggested that provisional stenting is the preferred method of therapy.^1-5 However, most studies of bifurcation lesions usually referred to the Medina classification (111 or 011) lesions. There are still many problems in the interventional treatment of ostial side-branch lesions (Medina 001) or aorta-ostial lesions. Percutaneous coronary intervention (PCI) of an ostial lesion requires precise implantation of a coronary artery stent in order to prevent adverse clinical outcomes.⁶ “Geographic miss” occurs when the ostial side-branch lesion is not fully covered by the stent. As a result of this miss, additional stents are required. The use of the additional stent results in stent overlap and may contribute to restenosis or adverse outcomes. Conversely, a stent placed too proximal into the main vessel may complicate future coronary intervention or lead to acute problems in the main branch. Currently, there are many techniques used by interventional cardiologists to approach this subset of ostial lesions. In this review, we outline different methods used for stent placement and discuss the advantages and disadvantages of these various approaches for precise ostial stent placement.

Why should the ostial lesion be treated?

Prior to starting and intervention on an ostial side branch, one needs to know: (1) what is the size of the side branch and the area of myocardium supplied? (2) What is the significance of the degree of stenosis of the ostial lesion and is there evidence of ischemia either based on stress testing or clinical symptoms that warrant treatment? (3) Would fractional flow reserve be required since the side-branch procedure may jeopardize the main branch?

Ostial lesion PCI techniques

A. Angiographically assisted placement. This is the most common technique used for ostial lesion stent placement. Often, precise placement is very difficult, large volumes of contrast and multiple views are required, and it is often unreliable. In a retrospective analysis of 100 ostial lesions, Dishmon et al⁷ found that the true ostium was missed in 54% of cases. Proximal miss was found in 52%, resulting in the inability to engage the guiding catheter in 93% of cases. Distal miss was found in 48% of cases, resulting in additional stents for 38% of cases. Furthermore, the target lesion revascularization (TLR) rates were increased 3-fold when compared to patients without geographic miss. This suggests that visual estimates with angiographic assistance for stent placement may not be the most precise way to treat ostial lesions. Figure 1 shows the use of angiographic-assisted placement in a side branch, but it is very obvious that the stent is protruding into the main vessel.

B. Ostial Pro Stent Placement System (for aorta-ostial lesion only). The Ostial-Pro (Merit Medical) is a nitinol device with expanded gold-plated feet for treatment of aorta-ostial lesions. It is advanced into the Toughy-Borst adapter using the supplied introducer to the primary curve in the guide catheter. The introducer is removed and a 0.014″ coronary wire is advanced distal to the lesion. The stent is placed on the 0.014″ wire and advanced distal to the lesion by 1-3 cm. The guide is than disengaged from the ostium and position is confirmed with a contrast test. Holding the stent and the wire, advance the Ostial Pro until the gold feet are out the distal end of the guide and pop open. Only the feet of the Ostial Pro should be out of the guide. Advance the guide catheter until the expanded feet of the Ostial Pro begin to flatten against the aortic wall. Holding the Ostial Pro, withdraw the stent until the proximal marker band is just distal to the guide. Confirm that the proximal stent is just distal to the gold feet of the device by another contrast injection and deploy the stent (Figure 2). Fischell and colleagues⁸ have reported 30 patients using the Ostial Pro stent placement system in ostial right coronary artery, ostial left main artery, and ostial saphenous vein graft lesions. They reported a high rate of success with excellent angiographic position. Although this device is user-friendly, angiographic guidance is still necessary for accurate stent positioning and often if the ostium of the treated vessel is not perpendicular to the aortic wall, the device does not work well. This device should be used in an angiographic view that is orthogonal to the device so that the proximal stent marker is aligned properly with the gold-plated feet of the Ostial Pro prior to stent deployment. More importantly, the long-term outcome of Ostial Pro-guided PCI is still unknown.

C. Aorta free-floating wire technique (for aorta-ostial lesion only). The guide catheter is inserted into the vessel and the first guidewire is passed down the vessel distal to the lesion. The second wire is inserted into the guide and advanced to the tip of the guide. The guide catheter is backed out of the ostium and the second wire is advanced into the aorta. This second wire acts as a marker for the ostium and prevents the guide from deeply engaging the vessel (Figure 3). Similar to other aorta ostial devices, there are no long-term outcome data.

D. Szabo (anchor-wire) technique. In 2005, Szabo reported a method of using two guidewires to enable optimal coverage of the ostium.^9,10 The guidewires are placed in the main branch and the side branch or in the aorta if an aorto-ostial lesion is being treated. Then, the stent is prepared by low-pressure inflation of the delivery balloon to raise the proximal cell of the stent outside the patient (Figure 4). The majority of the stent remains on the balloon and only the proximal cell is lifted from the delivery balloon. When the proximal end of the stent is seen to have lifted, the balloon is immediately deflated, leaving the proximal strut free. The proximal end of the guidewire positioned in the aorta or in the opposing branch is passed through this lifted stent strut and the stent is re-crimped on the delivery balloon. Gutierrez-Chico et al¹¹ reported their experience with 78 patients with Medina (010 or 001) or aorta-ostial lesions. They report an angiographic success rate of 100%. Acute procedural success was 86%, and 30-day procedural success was 78%. They believe the Szabo technique was more accurate than the angiographic technique of stent placement in avoiding geographic miss. This belief was based on the evaluation of the final stent position by angiography alone.

A recent paper by Vaquerizo B et al¹² suggests that the Szabo technique is not a predictable and precise method to use for implanting a stent at the ostium of a coronary artery. They reviewed 26 patients who underwent the Szabo technique for ostial stent placement. Angiographic success was achieved in only 88.5% (23/26). Angiographic binary restenosis was observed in two cases (11.1%) at a mean of 15 ± 5.0 months follow-up, and only 1 required revascularization for a TLR of (4.3%). A total of 3 adverse events were recorded, with a cumulative major adverse cardiac event (MACE) rate of 13% at 1 year. However, despite a seemingly excellent immediate angiographic result, intravascular ultrasound (IVUS) examination revealed significant stent protrusion. IVUS and angiographic assessment of restenosis at follow-up highlighted significant limitations of standard angiography to assess ostial lesions and final stent position.

Stent dislodgement has been reported as an infrequent complication. It is felt to be related to the stent manipulation that is needed to insert the proximal end of the anchor wire into the last cell of the stent and the re-crimping method. In in vitro models and in cases, the anchor wire may wrap around the stent and could potentially impede the advancement of the stent and cause stent dislodgement. It is very important to modify the plaque by predilation before stenting. This is done in order to assure that the double-wired stent movement will not be impeded by tortuosity, calcification, or other complicating features.

Micro computed tomography (CT) examination has revealed asymmetric deformation of the stent. This deformation leads to stent struts protruding into the side branch. In bench testing, the cell of the stent wired by the anchor side-branch guidewire underwent significant deformation at the level of the ostium and in the carina side of the vessel. The deformation will lead to non-uniform drug distribution.

As a result of data from IVUS, angiographic analysis of restenosis, and Micro CT bench testing, it may be concluded that the Szabo technique is a complex technique with relatively low immediate angiographic success (88.5%). When compared to other recent simpler techniques, mid-term results appear to be worse.

Despite the limitations of this technique, we still feel there is a role for the Szabo technique in ostial stent placement. Some of the pitfalls of the Szabo technique can be corrected. We believe that there is a steep learning curve for this technique before it can be applied efficiently in the treatment of all ostial lesions. Part of this learning curve is to gain the knowledge of which anatomy is not suitable for using the Szabo technique, such as tortuous vessels or calcified lesions. All lesions must be adequately predilated. To avoid stent dislodgement, the anchor wire can be inserted into the last stent strut without inflating the balloon. The stent should then be adequately re-crimped. The stent should be deployed at low pressure and the anchor wire should be removed using a balloon while applying pressure on the wire to avoid deformation. As a final step, postdilatation using a high-pressure balloon inflation is required to repair the stent.

E. T-stent and small protrusion technique (TAP). The ostial stent is placed to fully cover the ostium of the side branch with a slight protrusion of 1 mm into the main vessel (Figure 5). Accurate placement is often aided by placement of an uninflated balloon in the main vessel. The ostial stent is inflated once it is in position. This technique can be utilized with a single ostial stent for side-branch disease or as a two-stent approach in bifurcation lesions. When used as a two-stent technique, the main vessel is stented first. The side branch is re-wired and the stent cell across the side branch is dilated to allow passage of a stent into the side branch. An uninflated balloon is placed in the main branch and the side-branch stent is brought back to allow for a small protrusion into the main branch. After deployment of the side-branch stent, the delivery balloon is pulled back into the main vessel and both the main-vessel balloon and the side-branch balloon are inflated to allow for a final.

F. Cross-over 1-stent technique. This is the simplest technique when a stent is placed in the side branch and comes back into the main vessel (Figure 6). However, it leads to the risk of plaque shift from the carina into the main vessel. If the proximal vessel is much larger than the side branch, this mis-match can lead to stent malaposition in the main vessel. Optimization of the proximal portion of the stent often requires the use of a larger-size balloon. Occasionally, final kissing balloon inflations may be required to correct carina shift. If a dissection proximal to the stent occurs, then the procedure is shifted to a culotte two-stent procedure.

G. New dedicated ostial stent. Currently, there are several dedicated bifurcated stents in clinical trials that may be available in the next few years. For ostial side-branch lesions (Medina 001), the Cappella Sideguard stent (Cappella Inc.) appears to be the most promising.

The Cappella Sideguard device is a self-expanding nitinol stent that is deployed using a stent release sheath system (Figure 7).¹³ The Cappella Sideguard’s trumpet-shaped design helps the stent adhere to the ostium, allowing for complete stent-to-wall apposition. Its short length, self-expandable nitinol system, and low-profile delivery system allow greater deliverability even in a very tortuous vessel. Radiopaque markers located at the distal and proximal ends of the delivery system facilitate positioning of the stent at the side-branch ostium. A conventional stent is then placed in the main vessel. The side branch is re-accessed with a guidewire and the procedure is completed after final kissing balloon inflation. Serial IVUS analyses of the self-expanding bare-metal Sideguard stent indicate preserved side-branch ostial lumen dimensions at follow-up.¹⁴

Conclusions

We have highlighted several techniques used to position stents accurately in ostial lesions. However, no perfect technique or technologies allow for perfect ostial stent placement in 100% of cases. New dedicated bifurcation stent technology may not be clinically available for several more years. Currently, aorta-ostial lesions are easiest to approach using the aorta floating-wire technique. For a Medina 001 lesion, the crossover 1-stent technique seems to be the quickest and easiest method, to allow for safe full coverage of the ostium. The Szabo technique should be reserved for well-experienced operators with careful lesion selection and preparation.

References

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From the 1Beth Israel Medical Center, New York, New York and 2New York University, New York, New York.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.
Manuscript submitted February 6, 2012, provisional acceptance given February 14, 2012, final version accepted February 27, 2012.
Address correspondence to: Dr Tak W. Kwan, FSCAI, Senior Associate Director of Cardiac Catheterization Laboratory and Interventional Cardiology, Beth Israel Medical Center, 139 Centre St, Room 307, New York, NY 10013. Email: Kwancardio@aol.com