Stent Malapposition Frequent, But Without Clinical Consequences

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Some degree of stent malapposition—whether acute or late—occurs in virtually all cases of coronary DES implantation, but the clinical consequences are minimal to nonexistent, according to a single-center optical coherence tomographic (OCT) analysis appearing online January 14, 2014, ahead of print in Circulation: Cardiovascular Interventions.

Researchers led by Myeong-Ki Hong, MD, PhD, of Yonsei University College of Medicine (Seoul, South Korea), analyzed OCT images from 351 patients with 356 coronary lesions who received DES at their institution between January 2009 and December 2011. DES included sirolimus-eluting, zotarolimus-eluting, everolimus-eluting, and biolimus A9-eluting stents.

Acute Malapposition Found in Almost Two-Thirds

Over half (62%) demonstrated acute stent malapposition on OCT, while rates of late persistent malapposition and late-acquired stent malapposition were 31% and 16%, respectively. The rate of resolved acute stent malapposition was 69%.

Roughly half of acute stent malappositions (53%) were located within the edges of the stent. Percentage of acute malapposed struts was 5.2 ± 6.2%, and the volume of acute stent malapposition was 3.05 ± 3.67 mm³. Independent predictors of acute stent malapposition included:

• Calcification of the lesion (OR 11.19; 95% CI 3.52-35.63; P < 0.001)
• Long stent length (> 25 mm; OR 3.80; 95% CI 1.11-13.03; P = 0.033)
• Severe baseline diameter stenosis (> 70%; OR 2.45; 95% CI 1.19-5.06; P = 0.015)

Similarly, most late persistent stent malappositions were located within the edges of the stents (72%). The percentage of late-persistent malapposed struts was 2.5 ± 3.6%, and the volume of late-persistent  stent malapposition was 1.28 ± 2.16 mm³. On multivariate analysis, independent predictors of late-persistent malapposition included:

• Volume of acute stent malapposition (OR 1.17; 95% CI 1.01-1.35; P = 0.044)
• Location of acute stent malapposition within stent edges (OR 6.31; 95% CI 2.03-19.60; P = 0.001)

Acute Malapposition Volume Key Differentiator

Receiver operator curve analysis indicated that a volume of acute stent malapposition greater than 2.56 mm³ separated late persistent from resolved acute stent malapposition lesions (area under curve 0.739; 95% CI 0.768-0.819; sensitivity 62%, specificity 75%).

The percentage of late-acquired malapposed struts was 3.8 ± 4.5%, with a late-acquired malapposition stent volume of 2.06 ± 3.24 mm³. Late-acquired stent malappositions were predominantly distributed within stent bodies (61%) rather than stent edges (39%).

Clinical events possibly related to stent malapposition including CV death, nonfatal MI, and stent thrombosis were not observed in any patients with late stent malapposition over a mean follow-up of 28.6 ± 10.3 months. TLR was required in 8 cases.

In what the authors describe as the first study to investigate OCT-detected acute and late stent malapposition in a large number of patients in clinical practice, “The incidence of stent malapposition detected by OCT was relatively high.” However, they add, “Long-term clinical outcomes of late stent malapposition detected  by OCT were favorable.”

The high incidence of acute stent malapposition, in particular, according to Dr. Hong and colleagues, may be due to the ability of OCT to detect small lesions with greater accuracy than IVUS.

Factors Behind Lack of Clinical Consequences

Still, the clinical implications of stent malapposition are “controversial,” the authors claim, and their absence in the present study may stem from several factors:

• Most patients (75%) received dual antiplatelet therapy for at least 12 months
• Neointimal healing continued and malapposition was reduced during follow-up; In addition, dual antiplatelet therapy may have prevented some ischemic events until more favorable neointimal healing was achieved
• Smaller-sized stent malappositions that were frequently detected by OCT may not have clinically significant impact on future adverse CV events, as opposed to late stent thrombosis associated with larger-sized stent malapposition

Lastly, they note, seeing as a high proportion of lesions (77%) were implanted with new-generation DES, “Favorable clinical outcome, despite the presence of stent malapposition, may be because of the improved performance of new-generation DES.”

 

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Source:
Im E, Kim B-K, Ko Y-G, et al. Incidences, predictors, and clinical outcomes of acute and late stent malapposition detected by optical coherence tomography after drug-eluting stent implantation. Circ Cardiovasc Interv. 2014;Epub ahead of print.

 

Disclosures:

• The study was supported by a grant from the Korea Healthcare Technology R & D Project, Ministry for Health, Welfare and Family Affairs, Republic of South Korea, and the Cardiovascular Research Center, Seoul, South Korea.
• Dr. Hong reports no relevant conflicts of interest.

 

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• Incomplete Apposition Implicated in Stent Thrombosis
• IVUS-Directed Therapy Can Optimize Stent Placement Results
• Late Stent Malapposition More Common with DES