SES Fractures Raise Revascularization Risk, But Not Beyond 1 Year

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In patients implanted with sirolimus-eluting stents (SES), stent fracture increases the cumulative adverse event rate through 4 years. However, the difference is mainly driven by need for target lesion revascularization (TLR) within the first year after treatment, according to a paper published online August 2, 2011, ahead of print in Circulation: Cardiovascular Interventions.

For the study, researchers led by Hisashi Umeda, MD, PhD, of Toyota Memorial Hospital (Toyota, Japan), prospectively followed 925 patients who received Cypher SES (Cordis, Warren, NJ) for 874 lesions from June 2004 to June 2006. At 6 to 9 months, routine angiography was performed in 793 patients; baseline characteristics did not differ between patients who did and did not undergo imaging. Clinical follow-up through 4 years was obtained through medical records, telephone interviews, and information from referring physicians.

Different from the Start

Angiography revealed that stent fracture had occurred in 69 patients (8.7%) and 70 lesions (8.0%). Most fractures occurred at a single point within the lesion and were within 5 mm proximal or distal to the margins of stent overlap.

Patients who developed stent fracture were more likely to present with multivessel disease (82.6% vs. 64.0%; P = 0.002) and to have target lesions located in the right coronary artery (55.7% vs. 26.9%; P < 0.001), in tortuous vessels (68.6% vs. 19.4%; P < 0.001), and with chronic total occlusion (12.9% vs. 3.9%; P = 0.003). In contrast, baseline in-stent restenosis was more rare in stent fracture patients (2.9% vs. 10.8%; P = 0.035).

Procedural factors also varied by group, with a higher number of stents implanted per lesion in patients who went on to experience stent fracture (1.83 ± 0.74 vs. 1.25 ± 0.53; P < 0.001) as well as longer total stent length (38.5 ± 14.5 mm vs. 24.1 ± 10.1 mm; P < 0.001).

Fracture Linked to Restenosis, TLR

At 6- to 9-month follow-up, angiography also showed that lesions with stent fracture had greater in-stent late loss and a higher rate of in-stent restenosis than those who did not develop the complication (table 1). In patients with stent fracture, restenosis was observed at the fracture site in 87% of lesions.

Table 1. Angiographic Outcomes: Per Lesion Analysis

By 4 years, the cumulative MACE rate, comprising death, MI, and TLR, was higher in patients with stent fracture (23.2% vs. 12.6%; P = 0.014). The difference, however, was only apparent during the first year, and it was driven mainly by TLR. Between 1 and 4 years, adverse events including TLR occurred at similar levels in both groups (table 2).

Table 2. Clinical Outcomes: Per Patient Analysis

Academic Research Consortium-defined very late stent thrombosis rates were equivalent between patients with and without fracture at 2.9% and 1.4% (P = 0.281).

“In the pre-DES era, [stent fracture] was considered a rare event typically observed with the use of stents in anatomic locations associated with unique implant technique or when exposed to traumatic extravascular sources,” the investigators write, reporting that SES fracture rates range from 1.9% to 16.0% in today’s practice. Thus, the current study’s 8% rate falls somewhere in the middle.

Data Do Not Mesh with Clinical Practice

But in a telephone interview with TCTMD, Morton J. Kern, MD, of the University of California, Irvine (Irvine, CA), pointed out that 8% was approximately double what he would expect based on his own experience.

While stent fracture admittedly is an unfortunate occurrence, Dr. Kern said, “I’m not sure anybody is concerned about stent fracture very much because we just don’t see it.”

The study’s observation of low and similar long-term outcomes regardless of fracture may indicate that routine angiographic follow-up resulted in an unusually high fracture rate, he added, noting that “most people are doing pretty well” at 6 to 9 months. “Maybe that’s the issue: They’re seeing early problems and then treating them, whereas you might let some of these go if you didn’t do routine angiography.”

Dr. Kern said that stent fracture is usually identified when patients return with symptomatic restenosis, experience stent thrombosis, or have an incidental angiogram with renarrowing. In these instances, “of course, you would look to see if there was stent fracture,” he noted.

Fracture cannot be avoided through better technique, Dr. Kern explained. “It’s a function of where the stent is in the artery, what the lesion is made of—calcium or no calcium—or if it is on a tortuous curve, a calcified bend, or a high flex point,” he said. “Those would all be things that might predispose to a stent fracture.”

Dr. Kern was equally straightforward when asked about how to manage fracture once it occurs. “If [patients are] symptomatic, you go back in and stent right over it, to pound it down. That’s the only treatment we have,” he advised. “Most clinicians at this moment are not worried about it, at least I don’t hear talk of it in my circles.”

According to the study authors, the fact that fracture did little to influence long-term outcomes means that “even if [stent fracture] is identified, repeat revascularization should be considered carefully, dependent on clinical symptom, extent, and/or severity of myocardial ischemia on functional testing and associated anatomic severity of coronary lesions.

“Finally, no optimal intervention strategy (balloon angioplasty, bare-metal stents, homogeneous DES, or heterogeneous DES) of in-stent restenosis at fracture sites to date has been well established because there have been few studies on the topic,” Dr. Umeda and colleagues conclude in a slight departure from Dr. Kerns’ approach. “Avoidance of unnecessary long and/or overlapping SES implantation for lesions at high-risk for [stent fracture] might help prevent restenosis.”

Source:

Umeda H, Kawai T, Misumida N, et al. Impact of sirolimus-eluting stent fracture on 4-year clinical outcomes. Circ Cardiovasc Interv. 2011;4:349-354.

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