Stent Fractures Persist Among Newer-Generation Devices

Download this article's Factoid in PDF (& PPT for Gold Subscribers)

While praised for their safety and efficacy, everolimus-eluting stents (EES) nevertheless carry a low rate of device fracture, according to a study appearing on line September 25, 2012, ahead of print in Circulation: Cardiovascular Interventions. Such breaks, though rare, sharply increase the likelihood of adverse events.

Researchers led by Shoichi Kuramitsu, MD, of Kokura Memorial Hospital (Kitakyushu, Japan), looked at 1,035 patients (1,339 lesions) undergoing EES implantation (Xience V/Promus; Abbott Vascular/Boston Scientific) at 2 Japanese centers. All received follow-up angiography 6 to 9 months after the procedure. The vast majority of patients (97.5%) had stable angina, while almost three-fourths (72.1%) had single-vessel disease.

Stent fracture occurred in 39 lesions (2.9%) and 39 patients (3.8%). Over half (53.8%) were type 2 fractures, while a quarter (25.6%) were type 3, and a small minority (2.6%) were type 4. Two-thirds of the stent fractures (66.7%) were located in the midportion, with fewer located in the proximal and overlap portions (15.4% for each) or the distal portion (2.6%).

The MACE rate at 9 months was higher in patients with stent fracture compared with those that did not experience the complication, largely due to higher rates of MI, TLR, and stent thrombosis (table 1).

Table 1. MACE Within 9 Months of EES Implantation

^a Cardiac death, MI, clinically driven TLR, and stent thrombosis.

The difference in TLR was driven by PCI procedures (25.6% with stent fractures vs. 1.3% without stent fractures; P < 0.001); the need for CABG, meanwhile, was similar between groups (0 vs. 0.7%; P = NS). There was also no difference in early stent thrombosis (0 vs. 0.3%; P = NS). All stent thrombosis cases were definite; none were probable.

In addition, in-stent restenosis occurred more frequently in lesions that experienced stent fracture than in those that did not (71.8% vs. 4.9%; P < 0.001). In the fracture group, in-stent restenosis was observed at all fracture sites of all affected lesions.

On multivariable analysis, independent predictors of stent thrombosis after EES implantation included hinge motion, ostial stent location, tortuosity, and calcification (table 2).

Table 2. Independent Predictors of Stent Fracture

The study authors note that EES represent a new-generation class of DES with a thin-strut, flexible, cobalt chromium platform that “is expected to prevent [stent fracture].”

Nevertheless, the researchers add, the fracture rate found in the current study is consistent with those they observed in patients receiving sirolimus-eluting stents (4.1%) and paclitaxel-eluting stents (1.3%) at the same centers during the same time frame.

In terms of mechanism, Dr. Kuramitsu and colleagues note that 3 out of 39 cases of stent fracture were the result of longitudinal stent deformation, recognized in angiographic type 2 fractures using IVUS. “Therefore, [longitudinal deformation] may be one of the mechanisms for [stent fracture] in the thin-strut DES,” they write. “In any case, some few [stent fractures] are unavoidable, even in EES.”

What is most important, they stress, are the consequences of stent fracture, ie, the increased rates of MACE, TLR, and stent thrombosis. “Therefore, further improvements in stent design and materials are needed to prevent the occurrence of [stent fracture],” which the authors call “a rare but potentially life-threatening complication.” In particular, they note that “stent longitudinal integrity may be a key parameter in the development of newer-generation DES.”

Stent Fractures Here to Stay?

In a telephone interview with TCMTD, David E. Kandzari, MD, of the Piedmont Heart Institute (Atlanta, GA), agreed that stent fracture, while rare, may be a fact of life. “I think so, and the issue is we really don’t know the true frequency of its incidence unless patients undergo routine angiographic surveillance,” he said. “Even then, with the more modern-generation DES that have thinner strut thickness, it’s becoming more difficult to identify stent fracture at least by fluoroscopy because the stents themselves are so difficult to visualize.”

Nevertheless, the results do mean that “fracture likely occurs with all stent types, and in fact we’ve now seen this in DES clinical trials with nearly all DES,” Dr. Kandzari said. “In this report, like in others, the greater the lesion complexity, the greater the likelihood for stent fracture. This shows us, at least to date, that while stents arguably have evolved to provide better outcome, the underlying stent platform has not.”

He noted that in the current study, it is hard to determine how many of the fractures result from the stent itself or arise from Japanese practice patterns, which are characterized by long procedures and complex disease, with patients routinely brought back for angiographic surveillance.

Regardless, fracture rates with current DES may provide an unintended opportunity for another technology—bioabsorbable stents. Recent research has shown, Dr. Kandzari noted, “that the angulation of the artery is preserved and not distorted after implantation of a bioabsorbable stent, and perhaps permitting more natural contour of the vessel rather than distorting the architecture for luminal gain might be better over time than something more rigid and metallic.”

 

---

Source:
Kuramitsu S, Iwabuchi M, Haraguchi T, et al. Incidence and clinical impact of stent fracture after everolimus-eluting stent implantation. Circ Cardiovasc Interv. 2012;Epub ahead of print.

 

Disclosures:

• Dr. Kuramitsu reports no relevant conflicts of interest.
• Dr. Kandzari reports receiving research and grant support from Abbott Vascular, Boston Scientific, and Medtronic, and serving as a consultant for Boston Scientific and Medtronic.

 

Related Stories:

• SES Fractures Raise Revascularization Risk, But Not Beyond 1 Year
• DES Fractures Common, But Few Have Clinical Impact