The “Panic Stent”: A Stent that Goes Everywhere, All the Time, with any Guidewire, any Guiding Catheter and with any Operator

The dream of any interventional cardiologist and of most stent companies is to have or find a “Panic stent”. A stent with such unique deliverability may need to compromise with other characteristics such as recoil, radial strength, plaque coverage, and visibility, etc. The challenge is to make the most deliverable stent available that still maintains the attributes of a good stent. Since the disappearance of coil stents, which, in many ways, had the features most suitable to become the most deliverable stent, the position of leadership is shared by the stents with a ring design. At the present time, the need for a stent with a predictable deliverability is even more important than before, due to the expansion of stent indications, treatment of difficult and complex lesions and the extensive use of direct stenting.¹ In this issue of the Journal, Kobayashi et al. report their experience with the NIR w/SOX stent (Boston Scientific/Scimed, Maple Grove, Minnesota) in 88 patients with 102 coronary lesions.2 More than 2/3 of the lesions were complex; in 29% they were calcified, and in 25% a long stent was implanted. The procedural success was 96%, without specific mention to direct stenting. Most of the interest goes in examining the 4 cases in which this stent could not be delivered to the target lesion. The first one was a lesion at the anastomosis of a vein graft to a native vessel, which was successfully stented with an S670 (Medtronic AVE, Minneapolis, Minnesota). Two other lesions, in which a delivery failure occurred, were calcified and located in the right coronary artery. Despite aggressive predilatation and various attempts with a number of different stents, including a membrane-covered, self-expanding stent like the Radius (Boston Scientific/Scimed), which should minimize any friction in the context of severe calcifications, none of these two lesions could be stented. The last failure involved a severely calcified circumflex lesion. In this case, the stent failed to be delivered and dislodged from the balloon and a snare system had to be used for retrieval. The lesion was finally treated with balloon angioplasty. This specific case illustrates an important concept in interventional cardiology: With the possibility to examine a large number of cases, any possible complication will occur. An example of this is the loss of a stent, which, by definition, should be considered impossible to lose. The consequences of stent loss or failed delivery can be serious. A series of 1,303 consecutive procedures involving attempted coronary stenting were retrospectively reviewed. Failed stent deployment was defined as failure of the stent to be either delivered to or adequately deployed at the target lesion site. Deployment was unsuccessful in 108 (8.3%) cases involving 134 stents. In 87% of cases of failed delivery, attempts were made to withdraw the stent from the coronary artery. Stent retrieval was successful in 45%, peripheral embolization occurred in 38% of patients, and in 4% the stent dislodged in the left main artery. In 35% of cases, additional stent(s) were successfully deployed. Deployment failure was associated with an overall in-hospital adverse outcome in 19% of patients, including 16% urgent coronary artery bypass grafting, in 5% of non-fatal myocardial infarction, and 3 in-hospital deaths.3 The NIR w/SOX stent has a special sheath-like sleeve edge protection delivery system, which not only prevents stent flaring, but allows a safe retraction of the undeployed stent into the guiding catheter when necessary. This proximal and distal membrane should also lower any friction against calcium or metal present in the artery. In addition to facilitating deliverability, this type of delivery system allows a more appropriate stent expansion, which starts in the center with possible less trauma to the extremities of the stent. This type of complication occurs more frequently than seen with angiography.⁴ The lack of dog-boning, which the NIR w/SOX presents, may be an advantage in most lesions, but is a disadvantage in situations such as thrombus or fragile plaques, when the need to trap fragments may be important. A typical situation where this type of partially protected or covered stent is helpful is when the operator needs to deliver a stent distally to a deployed stent. In a recently reported series, six of 23 (23%) stents embolized during passage through a previously deployed stent.⁵ However, even the NIR w/SOX stent might not be enough to prevent stent dislodgement or guarantee 100% successful delivery. Despite this limitation, we should take into consideration that the NIR w/SOX was successfully delivered in 7 of 9 lesions when other stents failed. In two recent, randomized “stent versus stent” equivalency trials, the Multilink and NIR stents failed to demonstrate a statistically significant difference in delivery success rates compared to the Palmaz-Schatz stent.^6,7 An important difference between these trials and the current report is the NIR stent utilized in those randomized trials was not the one with the membrane coverage. The advantage of this membrane coverage is to overcome one limitation of this stent: the relative lack of flexibility compared to other stent design.⁸ The possibility to implant a stent with optimal radial strength9 and lesion coverage, even in complex and challenging anatomy, is an added advantage which may translate into a better long-term outcome . One of the most important lessons we can learn from this report is that most likely there is not a single stent which will prove with optimal deliverabilty for any type of lesion. In the situations where the NIR w/SOX could not be delivered while another stent was successful, and that the NIR w/SOX was the only stent which was advanced to other lesions, confirms the need not to focus on a single product. In some settings, flexibility may be the single most important feature, while in another anatomy, the lack of friction may become more important. This is the most likely explanation why the same device is effective in one lesion and not in another one.

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