Int J Cardiovasc Imaging DOI 10.1007/s10554-014-0557-y
ORIGINAL PAPER
Randomized comparison of acute stent malapposition between platinum–chromium versus cobalt–chromium everolimus-eluting stents Byeong-Keuk Kim • Dong-Ho Shin • Jung-Sun Kim • Young-Guk Ko • Donghoon Choi Yangsoo Jang • Myeong-Ki Hong
•
Received: 19 August 2014 / Accepted: 18 October 2014 Ó Springer Science+Business Media Dordrecht 2014
Abstract No randomized data exist regarding optical coherence tomography (OCT) evaluation immediately post-procedure and at the 3-month follow-up for platinum– chromium everolimus-eluting stents (PtCr-EES) versus cobalt-chromium everolimus-eluting stents (CoCr-EES). A total of 100 patients were randomly assigned to undergo PtCr-EES (n = 51) or CoCr-EES (n = 49) implantation. OCT was serially evaluated after stent deployment with nominal pressure and immediately post-procedure, and 3-month follow-up. The primary endpoint was the percentage of malapposed strut after nominal pressure and immediately post-procedure. Compared to the CoCr-EES, the PtCr-EES showed a lower tendency of percent malapposed strut at nominal pressure [median value (interquartile range); 4.1 % (0.5–11.7) vs. 7.6 % (2.9–13.7), p = 0.082] and immediately post–procedure [1.2 % (0–3.4) vs. 2.5 % (0.7–5.3), p = 0.051]. The percentage of cross sections with any malapposed struts was significantly lower with PtCr-EES at nominal pressure [15.0 % (5.6–39.0) vs. Byeong-Keuk Kim and Dong-Ho Shin have contributed equally to this article. B.-K. Kim D.-H. Shin J.-S. Kim Y.-G. Ko D. Choi Y. Jang M.-K. Hong (&) Division of Cardiology, Severance Cardiovascular Hospital, Yonsei University College of Medicine, 250 Seongsanno, Seodaemun-gu, Seoul 120-752, Korea e-mail: [email protected] B.-K. Kim D.-H. Shin J.-S. Kim Y.-G. Ko D. Choi Y. Jang M.-K. Hong Cardiovascular Institute, Yonsei University College of Medicine, Seoul, Korea Y. Jang M.-K. Hong Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Korea
23.8 % (18.2–44.4), p = 0.036] and immediately postprocedure [6.5 % (0–15.3) vs. 10.5 % (7.1–20.0), p = 0.026]. At the 3-month follow-up, both PtCr-EES and CoCr-EES showed comparable percentages of malapposed struts (0 vs. 0 %, respectively, p = 0.332) and uncovered struts (5.3 vs. 4.7 %, respectively, p = 0.829). We found a significant correlation between the immediate post-procedural percentage of malapposed struts versus the percentage of uncovered struts (r = 0.430, p \ 0.001) at the 3-month follow-up. Compared to the CoCr-EES, the PtCrEES shows a lower tendency toward a lower percentage of malapposed struts but no significant difference in strut coverage at the 3-month follow-up. The percentage of malapposed struts immediately post-procedure was correlated with strut coverage at the 3-month follow-up. Keywords Optical coherence tomography Stent Coronary artery disease
Introduction The thin strut-based cobalt–chromium everolimus-eluting stent (CoCr-EES) is a drug-eluting stent (DES) that has shown consistent efficacy and safety throughout many clinical trials [1–3]. However, the thinner-strut DES like CoCr-DESs may have potential concerns such as acute stent recoil and malapposition [4, 5]. Recently, a novel EES, the platinum–chromium everolimus-eluting stent (PtCr-EES) was developed. This type of stent uses a platinum chromium alloy, a different stent material from the CoCr-EES, and has shown a good angiographic and clinical outcomes [4, 6–8]. Compared to the CoCr-EES, PtCrEES provides a more enhanced stent visibility and improved deliverability [4, 9]. Although there have been
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some reports regarding the acute findings on intravascular ultrasound after DES implantation, these were single-arm study, intravascular ultrasound studies with a low resolution power for the evaluation of stent apposition, ones having the different primary endpoints, or focusing the late responses following DES implantation [1, 7, 10–13]. In addition, there have been no definite data comparing stent apposition in real world practice, not bench test. No randomized data exist regarding stent malapposition as analyzed with optical coherence tomography (OCT) having a superior resolution over intravascular ultrasound immediately post-procedure and at early follow-up times between CoCr-EES and PtCr-EES. Therefore, we performed a randomized study comparing OCT-detected stent malapposition after stent deployment with nominal pressure and immediately post-procedure between the two DESs. In addition, early stent strut coverage at the 3-month followup was compared using OCT.
Methods Study population This trial was a prospective, randomized, single-center study comparing OCT findings immediately post-procedure and at the 3-month follow-up after PtCr-EES versus CoCr-EES implantation (ClinicalTrials.gov identifier: NCT01581515). The patients who met the study criteria were randomly assigned to receive PtCr-EES (PROMUS ElementTM, Boston Scientific, Natick, MA, USA) or CoCrEES (Xience Prime, Abbott Vascular, Santa Clara, CA, USA). Serial OCT was performed following stent deployment with nominal pressure, immediately post-procedure, and at 3 months following DES implantation. Patients at least 20 years old with stable or unstable angina who were considered for percutaneous coronary intervention of a single de novo lesion with visually estimated stenosis of C70 % of the diameter were eligible for participation. Angiographic inclusion criteria were a reference vessel diameter of 2.5–3.5 mm and a lesion length \20 mm that could be covered by one 2.5- to 3.5-mm stent with a length B24 mm. Principal clinical exclusion criteria were: (1) acute myocardial infarction or hemodynamic instability; (2) history of any DES implantation within 3 months; (3) left ventricular ejection fraction \30 %; (4) severe hepatic dysfunction (three times normal reference values); (5) renal insufficiency (serum creatinine level C2.0 mg/dl or end-stage renal diseases); (6) contraindication to antiplatelet agents; (7) pregnant women or those with the potential for childbearing; and (8) life expectancy \1 year. Angiographic exclusion criteria were: (1) reference vessel diameter \2.5 or [4.0 mm; (2) diffuse long (stent length
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C28 mm) or multiple stenotic lesions requiring overlapping stents or implantation of multiple stents; and (3) complex lesion morphologies such as lesions at the aorto-ostium, unprotected left main, or graft with chronic total occlusion, thrombosis, restenosis, or heavily calcified lesions. This randomized study was approved by the institutional review board of our institution, and written informed consent was obtained from all enrolled patients. Randomization and coronary intervention procedures All participants fulfilling the enrollment criteria were randomized in a 1:1 ratio by an interactive web-based response system to receive a PtCr- or CoCr-EES immediately after coronary angiogram and before pre-dilation. The stratified randomization was done according to the estimated diameter and length of the DES needed to guarantee a balance between the two DES groups. To prevent the correlation and replications of lesions within patients, only one target lesion per patient was selected. All patients received at least 75 mg aspirin and a loading dose of 300 mg clopidogrel at least 12 h before intervention. Unfractionated heparin was administered to maintain an activated clotting time [250 s. All coronary intervention procedures were performed according to current standard techniques. After randomization, the assigned stent after balloon pre-dilation in all patients was implanted with nominal pressure, and then adjuvant higher-pressure postdilation was performed. The nominal pressure of PtCr-EES was 12 atm, irrespective of stent diameter. The nominal pressures of CoCr-EES were 8 atm in stent diameter of B2.75 mm and 10 atm in stent diameter of C3.0 mm. The determination of strategy of high-pressure post-dilation was left at the operators’ discretion. Although operators could see the OCT findings of the assigned stent, on-site strut-based analysis for evaluation of acute stent malapposition was not performed. After the procedure, dual antiplatelet therapy with aspirin 100 mg and clopidogrel 75 mg daily was prescribed for 12 months. Quantitative coronary angiography Quantitative coronary angiography analysis was performed before and after stent implantation and at the 3-month follow-up using an off-line quantitative coronary angiographic system (CASS System, Pie Medical Instruments, Maastricht, The Netherlands) in an independent core laboratory (Cardiovascular Research Center, Seoul, Korea). All analysts were blinded to the details of the patient and procedural information. Using the guiding catheter for magnification and calibration, reference vessel diameters and minimal luminal diameter were measured from diastolic frames in a single, matched view showing the smallest minimal luminal
Int J Cardiovasc Imaging
OCT examination was serially performed at each step: (1) immediately after stent deployment with nominal pressure, (2) immediately post-procedure, and (3) at the 3-month follow-up. OCT imaging of the target lesion was performed using a frequency-domain OCT system (C7-XR OCT imaging system, LightLab Imaging, Inc., St. Jude Medical, St. Paul, MN, USA), which was developed to generate frames at much higher rates and faster pullback speeds compared to time-domain OCT. In this study, OCT crosssectional images were generated at a rate of 100 frames/s, and the fiber was withdrawn at a speed of 20 mm/s within
the stationary imaging sheath. All OCT images were analyzed at a core laboratory (Cardiovascular Research Center, Seoul, Korea) by analysts who were blinded to the details of the patient and procedural information. Cross-sectional OCT images were analyzed at 1-mm intervals using a dedicated software program (QIvusÒ, Medis medical imaging systems Inc., Leiden, The Netherlands). Stent and lumen cross-sectional areas (CSAs) were measured manually; neointimal hyperplasia (NIH) CSA was calculated as the stent CSA minus luminal CSA. A malapposed strut was defined as a strut that had detached from the vessel wall by C100 lm for both PtCr-EES and CoCr-EES [4, 7, 14–16]. Regarding OCT analyses, three different-level analyses were performed in current study; strut-level, cross sectional-level, and lesion-level. For strut-level analysis, the percentage of malapposed struts was calculated as the ratio of malapposed struts to total struts in all OCT cross sections. For cross sectional-level analysis, the percentage of cross sections with any malapposed struts was assessed. For
Fig. 1 Representative images of stent malapposition analysis. Actual optical coherence tomography image with stent malapposition is shown in a and related analysis in b. Malapposed cross-sectional area
(CSA) was calculated as lumen CSA (outer circle) minus stent CSA (inner circle) [12.51–9.43 mm2] and total malapposed volume was calculated as the summation of malapposed CSA
diameter. Late loss was defined as the difference between post-procedure and follow-up minimal luminal diameter. Angiographic restenosis was defined as C50 % diameter stenosis inside the stent or stenosis of a 5-mm segment proximal or distal to the stent at the 3-month follow-up. OCT imaging and cross-sectional analysis
Fig. 2 Study summary and flow of the enrolled patients. OCT optical coherence tomography
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lesion-level analysis, stent malapposition was defined as a lesion with any malapposed strut on OCT. Stent malapposition was further classified into persistent, resolved, and late acquired by matching the immediately post-procedure and 3-month follow-up OCT images [17]. For the serial comparisons, total stent length was measured and unchanged stent length was confirmed in all lesions among OCT examinations and then cross-sectional OCT images at different stage of examinations were meticulously and manually matched using the distance from edge of stent and landmarks such as side branches or calcified plaques [17, 18]. Maximum malapposed CSA, distance between strut and vessel wall, total malapposed volume (summation of malapposed CSA), and maximum length of segments with malapposed struts (defined as the number of consecutive cross sections at 1-mm intervals with malapposed struts) were measured. Representative images of malapposition analysis are shown in Fig. 1. NIH thickness was measured as the distance between the endoluminal surface of the neointima and the strut, and an uncovered strut was defined as one with an NIH thickness of 0 lm [19]. The percentage of uncovered struts was calculated as the ratio of uncovered struts to total struts in all OCT cross sections. The maximum length of segments with uncovered struts was defined as the number of consecutive cross sections at 1-mm intervals with Table 1 Baseline clinical characteristics Variables
PtCr-EES (n = 51)
CoCr-EES (n = 49)
p
Age (years)
61 ± 8
59 ± 8
0.383
Men, n (%)
40 (78)
38 (78)
0.915
Hypertension, n (%)
30 (59)
26 (53)
0.562
Diabetes mellitus, n (%)
19 (37)
16 (33)
0.630
Dyslipidemia, n (%)
30 (59)
28 (57)
0.865
Current smokers, n (%)
10 (20)
15 (31)
0.204
Previous myocardial infarction, n (%)
2 (4)
1 (2)
Multi-vessel disease, n (%)
22 (43)
18 (37)
Stable angina, n (%)
37 (73)
37 (76)
Unstable angina, n (%) Discharge medication
14 (28)
12 (25)
Initial clinical presentation
uncovered struts. An intrastent thrombus was defined as an irregular mass protruding into the lumen (C250 lm at the thickest point) [20]. Study endpoints The primary endpoint of this study was the percentage of acute malapposed strut on OCT after stent deployment with nominal stent pressure and immediately post-procedure following stent implantation. Statistical analysis Continuous data were expressed as the mean ± standard deviation (SD) and compared with Student’s t tests. If the
Table 2 Baseline angiographic characteristics and quantitative angiographic analysis Variables
PtCr-EES (n = 51)
CoCr-EES (n = 49)
p
Number of lesions
51
49
–
Treated vessel, left anterior descending artery, n (%)
29 (57)
30 (61)
0.658
Balloon pre-dilation, n (%)
51 (100)
49 (100)
1.000
Size of balloon for pre-dilation (mm)
3.0 ± 0.4
3.1 ± 0.3
0.217
Stent diameter (mm)
3.3 ± 0.4
3.4 ± 0.4
0.199
Stent length (mm)
17.4 ± 3.3
18.7 ± 3.9
0.094
Adjunctive post-dilation, n (%)
51 (100)
49 (100)
1.000
Repeat adjunctive post-dilation, n (%)
4 (8)
4 (8)
0.953
Maximum inflation pressure (atm) Post-procedure
17.5 ± 4.1
17.3 ± 3.9
0.767
Lesion length (mm)
14.6 ± 3.3
15.7 ± 3.9
0.123
1.000
Reference vessel diameter (mm)
3.1 ± 0.4
3.2 ± 0.5
0.138
0.420
Pre-procedural minimum luminal diameter (mm)
0.9 ± 0.4
1.0 ± 0.4
0.149
Post-procedural minimum luminal diameter (mm)
3.0 ± 0.5
3.1 ± 0.4
0.274
Acute gain (mm)
2.0 ± 0.6
1.9 ± 1.0
0.399
0.736
Follow-up
Aspirin, n (%)
51 (100)
49 (100)
1.000
Angiogram follow-up, n (%)
48 (94)
47 (96)
1.000
Clopidogrel, n (%)
51 (100)
49 (100)
1.000
3.2 ± 0.4
0.134
33 (65)
36 (74)
0.344
Reference vessel diameter (mm)
3.1 ± 0.5
Beta-blockers, n (%) Angiotensin-converting enzyme or angiotensin receptor inhibitors, n (%)
35 (69)
33 (67)
0.891
Minimum luminal diameter (mm) Late loss (mm)
2.8 ± 0.5
2.9 ± 0.4
0.233
0.16 ± 0.31
0.13 ± 0.39
0.695
Statins, n (%)
51 (100)
49 (100)
1.000
Restenosis, n (%)
0 (0)
0 (0)
1.000
Values are presented as n (%) or mean ± SD
Values are presented as n (%), mean ± SD
PtCr-EES platinum–chromium everolimus-eluting stent, CoCr-EES cobalt–chromium everolimus-eluting stent
PtCr-EES platinum–chromium everolimus-eluting stent, CoCr-EES cobalt–chromium everolimus-eluting stent
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distributions were skewed, they were summarized as the median (interquartile range) and compared with the Mann– Whitney test. Categorical variables were presented as numbers (%) and compared with Chi square statistics or Fisher’s exact test as appropriate. Multilevel hierarchical linear model was applied for clustering problem and repeated measurements. Specifically, data of lesions, cross-sections and struts at each time point were modeled under each patient, a random effect variable. With this modeling, the clustering and correlation problems could be controlled. Pearson’s correlation analysis was performed to evaluate the relationship between the percentage of malapposed struts immediately post-procedure and the percentage of uncovered struts or the percentage of malapposed struts at the 3-month follow-up. A value of p \ 0.05 was considered statistically significant. Statistical analysis was performed with the Statistical Analysis System software (SAS; 9.1.3., SAS Institute, Cary, NC, USA) and R version 2.15.1 (R Development Core Team, Vienna, Austria, http://www.R-project.org).
Results A total of 100 patients were randomly assigned to receive a PtCr-EES (n = 51) or CoCr-EES (n = 49) between January 2012 and December 2012. During the same study period, percutaneous coronary intervention was performed in 1,153 patients who were screened for this study. Among
them, 1,053 patents were excluded following reason; left main disease in 72, chronic total occlusion in 50, graft vessel disease in 21, totally occluded thrombotic lesion in 120, bifurcation lesions requiring 2 stents in 42, ejection fraction \30 % in 43, chronic renal failure (creatinine level C2 mg/ dl) in 89, long lesion ([30 mm stent) or overlapping stents in 125, not suitable anatomy for OCT procedure in 146, refusal to participation in 20 and participating in other study protocols in 325 (708 exclusion criteria, 20 refusal to participation and 325 participating in other study protocols). A summary of the study flow is shown in Fig. 2. We found no significant differences in baseline clinical (Table 1) or angiographic (Table 2) characteristics between the two groups. OCT parameters were analyzed and compared using multilevel hierarchical linear model as well as Student t test or Mann–Whitney test. After stent deployment with nominal pressure, the incidence of stent malapposition with PtCr-EES was significantly lower than that of CoCr-EES (78 vs. 96 %, p = 0.015). Compared to the CoCr-EES, the PtCr-EES showed a tendency of lower percent malapposed strut at nominal pressure (7.6 vs. 4.1 %, p = 0.082), a significantly lower percentage of cross sections with a malapposed strut (23.8 vs. 15.0 %, p = 0.036) and a significantly lower maximum malapposed strut distance from the vessel wall (310 vs. 185 lm, p = 0.018). OCT findings immediately post-procedure showed that there was a lower tendency of percent malapposed strut at nominal pressure in PtCr-EES (1.2 vs. 2.5 % in CoCr-EES, p = 0.051); the
Table 3 Optical coherence tomographic findings after stent deployment with nominal pressure and immediately post-procedure Nominal pressure
Immediately post-procedure
PtCr-EES (n = 51)
CoCr-EES (n = 49)
p
PtCr-EES (n = 51)
CoCr-EES (n = 49)
p
Number of lesions, n
51
49
–
51
49
–
Total number of cross sections, n
820
833
–
831
846
–
Total number of analyzable struts, n Mean stent CSA (mm2)
8,697 6.3 ± 1.5
9,065 6.9 ± 1.6
– 0.061
8,795 7.6 ± 2.2
8,960 8.3 ± 2.2
– 0.094
Minimal stent CSA (mm2)
5.4 ± 1.6
5.9 ± 1.6
0.079
6.6 ± 2.1
7.1 ± 2.2
0.209
40 (78)
47 (96)
0.015
35 (69)
38 (78)
0.315
Malapposition analyses Stent malapposition, n (%) Percentage of malapposed struts
4.1 (0.5, 11.7)
7.6 (2.9, 13.7)
0.082
1.2 (0, 3.4)
2.5 (0.7, 5.3)
0.051
Cross sections with any malapposed struts (%)
15.0 (5.6, 39.0)
23.8 (18.2, 44.4)
0.036
6.5 (0, 15.3)
10.5 (7.1, 20.0)
0.026
Total malapposed volume (mm3)
15.6 (4.4, 25.7)
18.6 (13.7, 27.9)
0.121
8.9 (0, 21)
16.3 (7.7, 24.6)CS
0.087 0.277
2
Maximum malapposed CSA (mm )
0.6 (0.3, 1.4)
1.0 (0.5, 1.6)
0.141
0.5 (0, 0.9)
0.6 (0.4, 1)
Maximum malapposed distance (lm)
185 (113, 378)
310 (190, 530)
0.018
140 (0, 235)
190 (120, 320)
0.047
Maximum length of segments with malapposed struts (mm)
0.6 (0.2, 2.8)
1.0 (0.2, 2.0)
0.070
0.2 (0, 1.0)
0.2 (0.2, 2.0)
0.226
Values are presented as n (%), mean ± SD, or median (interquartile range) PtCr-EES platinum–chromium everolimus-eluting stent, CoCr-EES cobalt–chromium everolimus-eluting stent, CSA cross-sectional area
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PtCr-EES showed a significantly lower percentage of cross sections with a malapposed strut (6.5 vs. 10.5 % in CoCrEES, p = 0.026) and a lower maximum malapposed strut distance (140 vs. 190 lm in CoCr-EES, p = 0.047) (Table 3). As for the serial changes of malapposition from nominal pressure to immediate post-procedure, the mean percentage of malapposed strut significantly decreased for both PtCr-EES (7.8 % compared to 2.4 %, p \ 0.001) and CoCr-EES (8.7 % compared to 3.5 %, p \ 0.001). The mean percentages of the cross sections with any malapposed struts also significantly decreased for both PtCr-EES (24.4 % compared to 10.3 %, p \ 0.001) and CoCr-EES (31.3 % compared to 16.6 %, p \ 0.001). The changes of the percentages of malapposed struts (-5.4 ± 7.5 vs. -5.2 ± 6.0 %, p = 0.905) or the cross section with any malapposed struts (-14.1 ± 15.2 vs. -14.7 ± 16.1 %, p = 0.847) were not significantly different between PtCrand CoCr-EES. At the 3-month follow-up, both DESs showed the nearly improved percentages of malapposed strut on follow-up OCT (0 vs. 0 %, p = 0.332). The types of stent malapposition were similar between the two groups; the incidence of late-acquired stent malapposition was low in both DESs, and about half of acute stent malapposition were resolved. The percentage of uncovered struts in the two stents was not significantly different (5.3 % in PtCr-EES vs. 4.7 % in CoCr-EES, p = 0.829) (Table 4). Figure 3a shows the significant relationship between the percentage of malapposed struts immediately post-procedure and the percentage of uncovered struts at the 3-month follow-up (r = 0.430, p \ 0.001). In addition, a statistically significant correlation was noted between the percentage of malapposed struts immediately post-procedure and at the 3-month follow-up (r = 0.537, p \ 0.001) (Fig. 3b). During the 3-month clinical follow-up, no major adverse cardiac events such as death, myocardial infarction, or repeat revascularization occurred in either group.
Discussion The main findings of this study were that (1) compared to the CoCr-EES, the PtCr-EES showed a tendency of better strut apposition on OCT after stent deployment with nominal pressure and immediately post-procedure; (2) we found no significant differences in the percentages of uncovered or malapposed struts between the two DESs at the 3-month follow-up with OCT; (3) we found a significant correlation between the post-procedural percentage of malapposed struts and strut coverage at 3 months following DES implantation. The PtCr-EES, a novel EES that uses a platinum chromium alloy, has produced healthy vascular responses in
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Table 4 Optical coherence tomographic findings at 3 months
Number of patients followed, n
PtCr-EES (n = 51)
CoCr-EES (n = 49)
p
48 (94)
46 (94)
1.000
Duration followed (days)
98 ± 32
97 ± 28
0.866
Total number of cross sections, n
782
805
–
Total number of analyzable struts, n
8,007
8,304
–
Stent CSA (mm2)
7.7 ± 2.1
8.4 ± 2.3
0.102
Lumen CSA (mm2)
7.2 ± 2.0
7.9 ± 2.2
0.109
NIH CSA (mm2)
0.4 (0.3, 0.6)
0.4 (0.3, 0.5)
0.806
Percentage of NIH CSA (%)
5.9 (3.8, 8.7)
4.9 (4.2, 6.8)
0.518
NIH thickness (lm)
52 (37, 69)
45 (37, 74)
0.847
Presence of intrastent thrombi, n (%)
0 (0)
0 (0)
1.000
Percentage of uncovered struts
5.3 (1.9, 7.6)
4.7 (2.7, 7.8)
0.829
Both malapposed and uncovered struts (%)
0 (0, 0)
0 (0, 0.6)
0.143
Cross sections with any uncovered struts (%)
31.6 (10.8, 43.3)
29.6 (17.6, 43.5)
0.988
Cross sections with a ratio of uncovered to total struts [0.3 (%)
0 (0, 5.3)
0 (0, 8.5)
0.279
Maximum length of segments with uncovered struts (mm)
1.0 (0.2, 2.0)
1.0 (0.2, 2.9)
0.390
Percentage of malapposed struts
0 (0, 0.8)
0 (0, 1.2)
0.332
Change of percentage of malapposed struts from baseline to 3 months
1.3 ± 2.7
2.3 ± 2.9
0.102
Cross sections with any malapposed struts (%)
0 (0, 4.2)
0 (0, 6.4)
0.341
Total malapposed volume (mm3)
0 (0, 3.1)
0 (0, 10.8)
0.106
Maximum malapposed CSA (mm2)
0 (0, 0.3)
0 (0, 0.6)
0.138
Maximum malapposed distance (lm)
0 (0, 117.5)
0 (0, 0.2)
0.242
Uncovered struts analyses
Malapposition analyses
Types of stent malapposition, n (%)
0.488
Persistent, n (%)
11 (23)
16 (35)
Resolved, n (%)
22 (46)
21 (46)
Late acquired, n (%)
2 (4)
1 (2)
Values are presented as n (%), mean ± SD, or median (interquartile range) PtCr-EES platinum–chromium everolimus-eluting stent, CoCr-EES cobalt–chromium everolimus-eluting stent, CSA cross-sectional area, NIH neointimal hyperplasia
Int J Cardiovasc Imaging
Fig. 3 Association between the percentage of malapposed struts immediately post-procedure versus the percentage of uncovered struts (a) and the percentage of malapposed struts (b) at the 3-month follow-up
clinical studies as determined with OCT as well as comparable angiographic and clinical outcomes with the CoCrEES [6–9]. The PtCr-EES provides excellent deliverability, conformability, radiopacity, and radial strength with compression resistance [4, 6–9]. In particular, the material properties of platinum chromium, together with the design of the PtCr-EES, are expected to provide a superior capacity against stent recoil compared to current cobalt chromium alloy stent platforms such as CoCr-EES. Using a bench test, the recoil of the PtCr-EES is less than that of the CoCr-EES; 3.6 % for PtCr-EES versus 4.6 % for CoCrEES [9, 21]. Due to these characteristics of the PtCr-EES, this stent seems to provide better stent apposition and decrease post-procedural stent malapposition. However, only a few studies have produced randomized data regarding serial OCT evaluation of stent apposition from nominal pressure and immediately post-procedure to the early follow-up period. Prior studies investigating these issues were registry based or evaluated stent expansion using intravascular ultrasound [5, 7, 22]. In one intravascular ultrasound study [13], the rate of incomplete stent apposition at post-procedure with PtCr-EES (n = 88) was 5.7 %, which was lower than that of the CoCr-EES in previous studies [1, 7]. In a recent single-center, non-randomized OCT study (n = 42), acute responses to the PtCror CoCr-EES were similar with concentric expansion and a comparable incidence of stent malapposition between the two DESs [15]. Compared to the previous study [15], this study was randomized and evaluated serial OCT findings (particularly, at nominal pressure and immediately postprocedure). In the present study, although the primary endpoint, the percentage of malapposed struts, did not achieve statistical significance, the PtCr-EES showed a
better apposition on the other various OCT-measured stent malapposition parameters immediately after stent deployment with nominal pressure. Immediately post-procedural OCT after adjunctive post-dilation (all patients underwent adjunctive post-dilation) showed that the PtCr-EES produced a significantly lower percentage of cross sections with malapposed struts and a lower maximum malapposed strut distance. Acute stent malapposition detected with OCT is frequently observed and is resolved or persistent according to the degree of stent malapposition [17, 23]. Until now, there have been no established data regarding the impact of acute stent malapposition on the strut coverage at follow-up. This study showed a significant correlation between post-procedural stent apposition and 3-month follow-up strut coverage; these findings suggested that strut coverage on OCT in early follow-up periods after DES implantation could be improved by assessing stent apposition with OCT at the time of percutaneous coronary intervention. In lesions with greater amounts of acute stent malapposition, stent malapposition persisted without resolution and longer duration of dual antiplatelet treatment with potentially increased risk of bleeding might be subsequently required to prevent the occurrence of future adverse cardiac events [17, 24]. In a non-randomized study comparing clinical outcomes of percutaneous coronary intervention using angiographic guidance alone versus angiographic plus OCT guidance, angiographic plus OCT guidance was associated with a significant reduction in cardiac death or myocardial infarction [25]. Favorable clinical outcomes in patients with OCT-guided percutaneous coronary intervention may be partly explained by achieving superior strut coverage by reducing incomplete stent apposition with intra-procedural
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OCT. These relationships could be applied to the determination for the optimal duration of dual antiplatelet therapy after DES implantation. A future study investigating the relationship between the strut coverage at early period and the determination of dual antiplatelet therapy and its resultant clinical outcomes will be needed. The current study has some limitations. First, there was no specific strategy for pre-ballooning and high-pressure post-dilation in this study. In addition, although we found no significant differences in post-dilation strategies between the two DES groups, no standard criteria for OCTguided percutaneous coronary intervention have been established. Second, different nominal pressure in each DES may affect the OCT findings after stent deployment with nominal pressure. However, maximal inflation pressure immediately post-procedure was similar between the two groups. Third, there were no analyses comparing longitudinal foreshortening. Because recent publications have suggested that PtCr-EES could be more prone to longitudinal deformation than other platforms, there would be need for the randomized comparison in the real practices [26, 27]. Finally, the future study investigating the clinical implication for the difference of the ratio or incidence of malapposition between two DESs and the relation between malapposed and uncovered struts will be needed. In conclusion, this randomized study showed that acute stent malapposition was less frequently observed in PtCrEES-treated patients than in CoCr-EES-treated patients. Acknowledgments This study was supported by a grant from the Korea Healthcare Technology R&D Project, Ministry for Health, Welfare and Family Affairs, Republic of Korea (Nos. A085012, A102064), a grant from the Korea Health 21 R&D Project, Ministry of Health and Welfare, Republic of Korea (No. A085136), and the Cardiovascular Research Center, Seoul, Korea. Conflict of interest
4.
5.
6.
7.
8.
9.
10.
None. 11.
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22. Koo BK, Waseda K, Ako J, Hasegawa T, Shimohama T, Nakatani D, Otake H, Yamasaki M, Sakurai R, Tsujino I, Honda Y, Fitzgerald PJ (2010) Incidence of diffuse and focal chronic stent recoil after implantation of current generation bare-metal and drug-eluting stents. Int J Cardiol 144:132–134 23. Gutie´rrez-Chico JL, Wykrzykowska J, Nu¨esch E, van Geuns RJ, Koch KT, Koolen JJ, di Mario C, Windecker S, van Es GA, Gobbens P, Ju¨ni P, Regar E, Serruys PW (2012) Vascular tissue reaction to acute malapposition in human coronary arteries: sequential assessment with optical coherence tomography. Circ Cardiovasc Interv 5:20–29 24. Shin DH, Hong MK (2012) Optimal duration of dual antiplatelet therapy after drug-eluting stent implantation. Expert Rev Cardiovasc Ther 10:1273–1285 25. Prati F, Di Vito L, Biondi-Zoccai G, Occhipinti M, La Manna A, Tamburino C, Burzotta F, Trani C, Porto I, Ramazzotti V, Imola F, Manzoli A, Materia L, Cremonesi A, Albertucci M (2012) Angiography alone versus angiography plus optical coherence tomography to guide decision-making during percutaneous coronary intervention: the Centro per la Lotta contro l’InfartoOptimisation of Percutaneous Coronary Intervention (CLI-OPCI) study. EuroIntervention 8:823–829 26. Shannon J, Latib A, Takagi K, Chieffo A, Figini F, Sacco F, Ferrarello S, Montorfano M, Colombo A (2013) Procedural trauma risks longitudinal shortening of the Promus ElementTM stent platform. Catheter Cardiovasc Interv 81:810–817 27. Leibundgut G, Gick M, Toma A, Valina C, Lo¨ffelhardt N, Bu¨ttner HJ, Neumann FJ (2013) Longitudinal compression of the platinum–chromium everolimus-eluting stent during coronary implantation: predisposing mechanical properties, incidence, and predictors in a large patient cohort. Catheter Cardiovasc Interv 81:E206–E214
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ORIGINAL PAPER
Randomized comparison of acute stent malapposition between platinum–chromium versus cobalt–chromium everolimus-eluting stents Byeong-Keuk Kim • Dong-Ho Shin • Jung-Sun Kim • Young-Guk Ko • Donghoon Choi Yangsoo Jang • Myeong-Ki Hong
•
Received: 19 August 2014 / Accepted: 18 October 2014 Ó Springer Science+Business Media Dordrecht 2014
Abstract No randomized data exist regarding optical coherence tomography (OCT) evaluation immediately post-procedure and at the 3-month follow-up for platinum– chromium everolimus-eluting stents (PtCr-EES) versus cobalt-chromium everolimus-eluting stents (CoCr-EES). A total of 100 patients were randomly assigned to undergo PtCr-EES (n = 51) or CoCr-EES (n = 49) implantation. OCT was serially evaluated after stent deployment with nominal pressure and immediately post-procedure, and 3-month follow-up. The primary endpoint was the percentage of malapposed strut after nominal pressure and immediately post-procedure. Compared to the CoCr-EES, the PtCr-EES showed a lower tendency of percent malapposed strut at nominal pressure [median value (interquartile range); 4.1 % (0.5–11.7) vs. 7.6 % (2.9–13.7), p = 0.082] and immediately post–procedure [1.2 % (0–3.4) vs. 2.5 % (0.7–5.3), p = 0.051]. The percentage of cross sections with any malapposed struts was significantly lower with PtCr-EES at nominal pressure [15.0 % (5.6–39.0) vs. Byeong-Keuk Kim and Dong-Ho Shin have contributed equally to this article. B.-K. Kim D.-H. Shin J.-S. Kim Y.-G. Ko D. Choi Y. Jang M.-K. Hong (&) Division of Cardiology, Severance Cardiovascular Hospital, Yonsei University College of Medicine, 250 Seongsanno, Seodaemun-gu, Seoul 120-752, Korea e-mail: [email protected] B.-K. Kim D.-H. Shin J.-S. Kim Y.-G. Ko D. Choi Y. Jang M.-K. Hong Cardiovascular Institute, Yonsei University College of Medicine, Seoul, Korea Y. Jang M.-K. Hong Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Korea
23.8 % (18.2–44.4), p = 0.036] and immediately postprocedure [6.5 % (0–15.3) vs. 10.5 % (7.1–20.0), p = 0.026]. At the 3-month follow-up, both PtCr-EES and CoCr-EES showed comparable percentages of malapposed struts (0 vs. 0 %, respectively, p = 0.332) and uncovered struts (5.3 vs. 4.7 %, respectively, p = 0.829). We found a significant correlation between the immediate post-procedural percentage of malapposed struts versus the percentage of uncovered struts (r = 0.430, p \ 0.001) at the 3-month follow-up. Compared to the CoCr-EES, the PtCrEES shows a lower tendency toward a lower percentage of malapposed struts but no significant difference in strut coverage at the 3-month follow-up. The percentage of malapposed struts immediately post-procedure was correlated with strut coverage at the 3-month follow-up. Keywords Optical coherence tomography Stent Coronary artery disease
Introduction The thin strut-based cobalt–chromium everolimus-eluting stent (CoCr-EES) is a drug-eluting stent (DES) that has shown consistent efficacy and safety throughout many clinical trials [1–3]. However, the thinner-strut DES like CoCr-DESs may have potential concerns such as acute stent recoil and malapposition [4, 5]. Recently, a novel EES, the platinum–chromium everolimus-eluting stent (PtCr-EES) was developed. This type of stent uses a platinum chromium alloy, a different stent material from the CoCr-EES, and has shown a good angiographic and clinical outcomes [4, 6–8]. Compared to the CoCr-EES, PtCrEES provides a more enhanced stent visibility and improved deliverability [4, 9]. Although there have been
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some reports regarding the acute findings on intravascular ultrasound after DES implantation, these were single-arm study, intravascular ultrasound studies with a low resolution power for the evaluation of stent apposition, ones having the different primary endpoints, or focusing the late responses following DES implantation [1, 7, 10–13]. In addition, there have been no definite data comparing stent apposition in real world practice, not bench test. No randomized data exist regarding stent malapposition as analyzed with optical coherence tomography (OCT) having a superior resolution over intravascular ultrasound immediately post-procedure and at early follow-up times between CoCr-EES and PtCr-EES. Therefore, we performed a randomized study comparing OCT-detected stent malapposition after stent deployment with nominal pressure and immediately post-procedure between the two DESs. In addition, early stent strut coverage at the 3-month followup was compared using OCT.
Methods Study population This trial was a prospective, randomized, single-center study comparing OCT findings immediately post-procedure and at the 3-month follow-up after PtCr-EES versus CoCr-EES implantation (ClinicalTrials.gov identifier: NCT01581515). The patients who met the study criteria were randomly assigned to receive PtCr-EES (PROMUS ElementTM, Boston Scientific, Natick, MA, USA) or CoCrEES (Xience Prime, Abbott Vascular, Santa Clara, CA, USA). Serial OCT was performed following stent deployment with nominal pressure, immediately post-procedure, and at 3 months following DES implantation. Patients at least 20 years old with stable or unstable angina who were considered for percutaneous coronary intervention of a single de novo lesion with visually estimated stenosis of C70 % of the diameter were eligible for participation. Angiographic inclusion criteria were a reference vessel diameter of 2.5–3.5 mm and a lesion length \20 mm that could be covered by one 2.5- to 3.5-mm stent with a length B24 mm. Principal clinical exclusion criteria were: (1) acute myocardial infarction or hemodynamic instability; (2) history of any DES implantation within 3 months; (3) left ventricular ejection fraction \30 %; (4) severe hepatic dysfunction (three times normal reference values); (5) renal insufficiency (serum creatinine level C2.0 mg/dl or end-stage renal diseases); (6) contraindication to antiplatelet agents; (7) pregnant women or those with the potential for childbearing; and (8) life expectancy \1 year. Angiographic exclusion criteria were: (1) reference vessel diameter \2.5 or [4.0 mm; (2) diffuse long (stent length
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C28 mm) or multiple stenotic lesions requiring overlapping stents or implantation of multiple stents; and (3) complex lesion morphologies such as lesions at the aorto-ostium, unprotected left main, or graft with chronic total occlusion, thrombosis, restenosis, or heavily calcified lesions. This randomized study was approved by the institutional review board of our institution, and written informed consent was obtained from all enrolled patients. Randomization and coronary intervention procedures All participants fulfilling the enrollment criteria were randomized in a 1:1 ratio by an interactive web-based response system to receive a PtCr- or CoCr-EES immediately after coronary angiogram and before pre-dilation. The stratified randomization was done according to the estimated diameter and length of the DES needed to guarantee a balance between the two DES groups. To prevent the correlation and replications of lesions within patients, only one target lesion per patient was selected. All patients received at least 75 mg aspirin and a loading dose of 300 mg clopidogrel at least 12 h before intervention. Unfractionated heparin was administered to maintain an activated clotting time [250 s. All coronary intervention procedures were performed according to current standard techniques. After randomization, the assigned stent after balloon pre-dilation in all patients was implanted with nominal pressure, and then adjuvant higher-pressure postdilation was performed. The nominal pressure of PtCr-EES was 12 atm, irrespective of stent diameter. The nominal pressures of CoCr-EES were 8 atm in stent diameter of B2.75 mm and 10 atm in stent diameter of C3.0 mm. The determination of strategy of high-pressure post-dilation was left at the operators’ discretion. Although operators could see the OCT findings of the assigned stent, on-site strut-based analysis for evaluation of acute stent malapposition was not performed. After the procedure, dual antiplatelet therapy with aspirin 100 mg and clopidogrel 75 mg daily was prescribed for 12 months. Quantitative coronary angiography Quantitative coronary angiography analysis was performed before and after stent implantation and at the 3-month follow-up using an off-line quantitative coronary angiographic system (CASS System, Pie Medical Instruments, Maastricht, The Netherlands) in an independent core laboratory (Cardiovascular Research Center, Seoul, Korea). All analysts were blinded to the details of the patient and procedural information. Using the guiding catheter for magnification and calibration, reference vessel diameters and minimal luminal diameter were measured from diastolic frames in a single, matched view showing the smallest minimal luminal
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OCT examination was serially performed at each step: (1) immediately after stent deployment with nominal pressure, (2) immediately post-procedure, and (3) at the 3-month follow-up. OCT imaging of the target lesion was performed using a frequency-domain OCT system (C7-XR OCT imaging system, LightLab Imaging, Inc., St. Jude Medical, St. Paul, MN, USA), which was developed to generate frames at much higher rates and faster pullback speeds compared to time-domain OCT. In this study, OCT crosssectional images were generated at a rate of 100 frames/s, and the fiber was withdrawn at a speed of 20 mm/s within
the stationary imaging sheath. All OCT images were analyzed at a core laboratory (Cardiovascular Research Center, Seoul, Korea) by analysts who were blinded to the details of the patient and procedural information. Cross-sectional OCT images were analyzed at 1-mm intervals using a dedicated software program (QIvusÒ, Medis medical imaging systems Inc., Leiden, The Netherlands). Stent and lumen cross-sectional areas (CSAs) were measured manually; neointimal hyperplasia (NIH) CSA was calculated as the stent CSA minus luminal CSA. A malapposed strut was defined as a strut that had detached from the vessel wall by C100 lm for both PtCr-EES and CoCr-EES [4, 7, 14–16]. Regarding OCT analyses, three different-level analyses were performed in current study; strut-level, cross sectional-level, and lesion-level. For strut-level analysis, the percentage of malapposed struts was calculated as the ratio of malapposed struts to total struts in all OCT cross sections. For cross sectional-level analysis, the percentage of cross sections with any malapposed struts was assessed. For
Fig. 1 Representative images of stent malapposition analysis. Actual optical coherence tomography image with stent malapposition is shown in a and related analysis in b. Malapposed cross-sectional area
(CSA) was calculated as lumen CSA (outer circle) minus stent CSA (inner circle) [12.51–9.43 mm2] and total malapposed volume was calculated as the summation of malapposed CSA
diameter. Late loss was defined as the difference between post-procedure and follow-up minimal luminal diameter. Angiographic restenosis was defined as C50 % diameter stenosis inside the stent or stenosis of a 5-mm segment proximal or distal to the stent at the 3-month follow-up. OCT imaging and cross-sectional analysis
Fig. 2 Study summary and flow of the enrolled patients. OCT optical coherence tomography
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lesion-level analysis, stent malapposition was defined as a lesion with any malapposed strut on OCT. Stent malapposition was further classified into persistent, resolved, and late acquired by matching the immediately post-procedure and 3-month follow-up OCT images [17]. For the serial comparisons, total stent length was measured and unchanged stent length was confirmed in all lesions among OCT examinations and then cross-sectional OCT images at different stage of examinations were meticulously and manually matched using the distance from edge of stent and landmarks such as side branches or calcified plaques [17, 18]. Maximum malapposed CSA, distance between strut and vessel wall, total malapposed volume (summation of malapposed CSA), and maximum length of segments with malapposed struts (defined as the number of consecutive cross sections at 1-mm intervals with malapposed struts) were measured. Representative images of malapposition analysis are shown in Fig. 1. NIH thickness was measured as the distance between the endoluminal surface of the neointima and the strut, and an uncovered strut was defined as one with an NIH thickness of 0 lm [19]. The percentage of uncovered struts was calculated as the ratio of uncovered struts to total struts in all OCT cross sections. The maximum length of segments with uncovered struts was defined as the number of consecutive cross sections at 1-mm intervals with Table 1 Baseline clinical characteristics Variables
PtCr-EES (n = 51)
CoCr-EES (n = 49)
p
Age (years)
61 ± 8
59 ± 8
0.383
Men, n (%)
40 (78)
38 (78)
0.915
Hypertension, n (%)
30 (59)
26 (53)
0.562
Diabetes mellitus, n (%)
19 (37)
16 (33)
0.630
Dyslipidemia, n (%)
30 (59)
28 (57)
0.865
Current smokers, n (%)
10 (20)
15 (31)
0.204
Previous myocardial infarction, n (%)
2 (4)
1 (2)
Multi-vessel disease, n (%)
22 (43)
18 (37)
Stable angina, n (%)
37 (73)
37 (76)
Unstable angina, n (%) Discharge medication
14 (28)
12 (25)
Initial clinical presentation
uncovered struts. An intrastent thrombus was defined as an irregular mass protruding into the lumen (C250 lm at the thickest point) [20]. Study endpoints The primary endpoint of this study was the percentage of acute malapposed strut on OCT after stent deployment with nominal stent pressure and immediately post-procedure following stent implantation. Statistical analysis Continuous data were expressed as the mean ± standard deviation (SD) and compared with Student’s t tests. If the
Table 2 Baseline angiographic characteristics and quantitative angiographic analysis Variables
PtCr-EES (n = 51)
CoCr-EES (n = 49)
p
Number of lesions
51
49
–
Treated vessel, left anterior descending artery, n (%)
29 (57)
30 (61)
0.658
Balloon pre-dilation, n (%)
51 (100)
49 (100)
1.000
Size of balloon for pre-dilation (mm)
3.0 ± 0.4
3.1 ± 0.3
0.217
Stent diameter (mm)
3.3 ± 0.4
3.4 ± 0.4
0.199
Stent length (mm)
17.4 ± 3.3
18.7 ± 3.9
0.094
Adjunctive post-dilation, n (%)
51 (100)
49 (100)
1.000
Repeat adjunctive post-dilation, n (%)
4 (8)
4 (8)
0.953
Maximum inflation pressure (atm) Post-procedure
17.5 ± 4.1
17.3 ± 3.9
0.767
Lesion length (mm)
14.6 ± 3.3
15.7 ± 3.9
0.123
1.000
Reference vessel diameter (mm)
3.1 ± 0.4
3.2 ± 0.5
0.138
0.420
Pre-procedural minimum luminal diameter (mm)
0.9 ± 0.4
1.0 ± 0.4
0.149
Post-procedural minimum luminal diameter (mm)
3.0 ± 0.5
3.1 ± 0.4
0.274
Acute gain (mm)
2.0 ± 0.6
1.9 ± 1.0
0.399
0.736
Follow-up
Aspirin, n (%)
51 (100)
49 (100)
1.000
Angiogram follow-up, n (%)
48 (94)
47 (96)
1.000
Clopidogrel, n (%)
51 (100)
49 (100)
1.000
3.2 ± 0.4
0.134
33 (65)
36 (74)
0.344
Reference vessel diameter (mm)
3.1 ± 0.5
Beta-blockers, n (%) Angiotensin-converting enzyme or angiotensin receptor inhibitors, n (%)
35 (69)
33 (67)
0.891
Minimum luminal diameter (mm) Late loss (mm)
2.8 ± 0.5
2.9 ± 0.4
0.233
0.16 ± 0.31
0.13 ± 0.39
0.695
Statins, n (%)
51 (100)
49 (100)
1.000
Restenosis, n (%)
0 (0)
0 (0)
1.000
Values are presented as n (%) or mean ± SD
Values are presented as n (%), mean ± SD
PtCr-EES platinum–chromium everolimus-eluting stent, CoCr-EES cobalt–chromium everolimus-eluting stent
PtCr-EES platinum–chromium everolimus-eluting stent, CoCr-EES cobalt–chromium everolimus-eluting stent
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distributions were skewed, they were summarized as the median (interquartile range) and compared with the Mann– Whitney test. Categorical variables were presented as numbers (%) and compared with Chi square statistics or Fisher’s exact test as appropriate. Multilevel hierarchical linear model was applied for clustering problem and repeated measurements. Specifically, data of lesions, cross-sections and struts at each time point were modeled under each patient, a random effect variable. With this modeling, the clustering and correlation problems could be controlled. Pearson’s correlation analysis was performed to evaluate the relationship between the percentage of malapposed struts immediately post-procedure and the percentage of uncovered struts or the percentage of malapposed struts at the 3-month follow-up. A value of p \ 0.05 was considered statistically significant. Statistical analysis was performed with the Statistical Analysis System software (SAS; 9.1.3., SAS Institute, Cary, NC, USA) and R version 2.15.1 (R Development Core Team, Vienna, Austria, http://www.R-project.org).
Results A total of 100 patients were randomly assigned to receive a PtCr-EES (n = 51) or CoCr-EES (n = 49) between January 2012 and December 2012. During the same study period, percutaneous coronary intervention was performed in 1,153 patients who were screened for this study. Among
them, 1,053 patents were excluded following reason; left main disease in 72, chronic total occlusion in 50, graft vessel disease in 21, totally occluded thrombotic lesion in 120, bifurcation lesions requiring 2 stents in 42, ejection fraction \30 % in 43, chronic renal failure (creatinine level C2 mg/ dl) in 89, long lesion ([30 mm stent) or overlapping stents in 125, not suitable anatomy for OCT procedure in 146, refusal to participation in 20 and participating in other study protocols in 325 (708 exclusion criteria, 20 refusal to participation and 325 participating in other study protocols). A summary of the study flow is shown in Fig. 2. We found no significant differences in baseline clinical (Table 1) or angiographic (Table 2) characteristics between the two groups. OCT parameters were analyzed and compared using multilevel hierarchical linear model as well as Student t test or Mann–Whitney test. After stent deployment with nominal pressure, the incidence of stent malapposition with PtCr-EES was significantly lower than that of CoCr-EES (78 vs. 96 %, p = 0.015). Compared to the CoCr-EES, the PtCr-EES showed a tendency of lower percent malapposed strut at nominal pressure (7.6 vs. 4.1 %, p = 0.082), a significantly lower percentage of cross sections with a malapposed strut (23.8 vs. 15.0 %, p = 0.036) and a significantly lower maximum malapposed strut distance from the vessel wall (310 vs. 185 lm, p = 0.018). OCT findings immediately post-procedure showed that there was a lower tendency of percent malapposed strut at nominal pressure in PtCr-EES (1.2 vs. 2.5 % in CoCr-EES, p = 0.051); the
Table 3 Optical coherence tomographic findings after stent deployment with nominal pressure and immediately post-procedure Nominal pressure
Immediately post-procedure
PtCr-EES (n = 51)
CoCr-EES (n = 49)
p
PtCr-EES (n = 51)
CoCr-EES (n = 49)
p
Number of lesions, n
51
49
–
51
49
–
Total number of cross sections, n
820
833
–
831
846
–
Total number of analyzable struts, n Mean stent CSA (mm2)
8,697 6.3 ± 1.5
9,065 6.9 ± 1.6
– 0.061
8,795 7.6 ± 2.2
8,960 8.3 ± 2.2
– 0.094
Minimal stent CSA (mm2)
5.4 ± 1.6
5.9 ± 1.6
0.079
6.6 ± 2.1
7.1 ± 2.2
0.209
40 (78)
47 (96)
0.015
35 (69)
38 (78)
0.315
Malapposition analyses Stent malapposition, n (%) Percentage of malapposed struts
4.1 (0.5, 11.7)
7.6 (2.9, 13.7)
0.082
1.2 (0, 3.4)
2.5 (0.7, 5.3)
0.051
Cross sections with any malapposed struts (%)
15.0 (5.6, 39.0)
23.8 (18.2, 44.4)
0.036
6.5 (0, 15.3)
10.5 (7.1, 20.0)
0.026
Total malapposed volume (mm3)
15.6 (4.4, 25.7)
18.6 (13.7, 27.9)
0.121
8.9 (0, 21)
16.3 (7.7, 24.6)CS
0.087 0.277
2
Maximum malapposed CSA (mm )
0.6 (0.3, 1.4)
1.0 (0.5, 1.6)
0.141
0.5 (0, 0.9)
0.6 (0.4, 1)
Maximum malapposed distance (lm)
185 (113, 378)
310 (190, 530)
0.018
140 (0, 235)
190 (120, 320)
0.047
Maximum length of segments with malapposed struts (mm)
0.6 (0.2, 2.8)
1.0 (0.2, 2.0)
0.070
0.2 (0, 1.0)
0.2 (0.2, 2.0)
0.226
Values are presented as n (%), mean ± SD, or median (interquartile range) PtCr-EES platinum–chromium everolimus-eluting stent, CoCr-EES cobalt–chromium everolimus-eluting stent, CSA cross-sectional area
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PtCr-EES showed a significantly lower percentage of cross sections with a malapposed strut (6.5 vs. 10.5 % in CoCrEES, p = 0.026) and a lower maximum malapposed strut distance (140 vs. 190 lm in CoCr-EES, p = 0.047) (Table 3). As for the serial changes of malapposition from nominal pressure to immediate post-procedure, the mean percentage of malapposed strut significantly decreased for both PtCr-EES (7.8 % compared to 2.4 %, p \ 0.001) and CoCr-EES (8.7 % compared to 3.5 %, p \ 0.001). The mean percentages of the cross sections with any malapposed struts also significantly decreased for both PtCr-EES (24.4 % compared to 10.3 %, p \ 0.001) and CoCr-EES (31.3 % compared to 16.6 %, p \ 0.001). The changes of the percentages of malapposed struts (-5.4 ± 7.5 vs. -5.2 ± 6.0 %, p = 0.905) or the cross section with any malapposed struts (-14.1 ± 15.2 vs. -14.7 ± 16.1 %, p = 0.847) were not significantly different between PtCrand CoCr-EES. At the 3-month follow-up, both DESs showed the nearly improved percentages of malapposed strut on follow-up OCT (0 vs. 0 %, p = 0.332). The types of stent malapposition were similar between the two groups; the incidence of late-acquired stent malapposition was low in both DESs, and about half of acute stent malapposition were resolved. The percentage of uncovered struts in the two stents was not significantly different (5.3 % in PtCr-EES vs. 4.7 % in CoCr-EES, p = 0.829) (Table 4). Figure 3a shows the significant relationship between the percentage of malapposed struts immediately post-procedure and the percentage of uncovered struts at the 3-month follow-up (r = 0.430, p \ 0.001). In addition, a statistically significant correlation was noted between the percentage of malapposed struts immediately post-procedure and at the 3-month follow-up (r = 0.537, p \ 0.001) (Fig. 3b). During the 3-month clinical follow-up, no major adverse cardiac events such as death, myocardial infarction, or repeat revascularization occurred in either group.
Discussion The main findings of this study were that (1) compared to the CoCr-EES, the PtCr-EES showed a tendency of better strut apposition on OCT after stent deployment with nominal pressure and immediately post-procedure; (2) we found no significant differences in the percentages of uncovered or malapposed struts between the two DESs at the 3-month follow-up with OCT; (3) we found a significant correlation between the post-procedural percentage of malapposed struts and strut coverage at 3 months following DES implantation. The PtCr-EES, a novel EES that uses a platinum chromium alloy, has produced healthy vascular responses in
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Table 4 Optical coherence tomographic findings at 3 months
Number of patients followed, n
PtCr-EES (n = 51)
CoCr-EES (n = 49)
p
48 (94)
46 (94)
1.000
Duration followed (days)
98 ± 32
97 ± 28
0.866
Total number of cross sections, n
782
805
–
Total number of analyzable struts, n
8,007
8,304
–
Stent CSA (mm2)
7.7 ± 2.1
8.4 ± 2.3
0.102
Lumen CSA (mm2)
7.2 ± 2.0
7.9 ± 2.2
0.109
NIH CSA (mm2)
0.4 (0.3, 0.6)
0.4 (0.3, 0.5)
0.806
Percentage of NIH CSA (%)
5.9 (3.8, 8.7)
4.9 (4.2, 6.8)
0.518
NIH thickness (lm)
52 (37, 69)
45 (37, 74)
0.847
Presence of intrastent thrombi, n (%)
0 (0)
0 (0)
1.000
Percentage of uncovered struts
5.3 (1.9, 7.6)
4.7 (2.7, 7.8)
0.829
Both malapposed and uncovered struts (%)
0 (0, 0)
0 (0, 0.6)
0.143
Cross sections with any uncovered struts (%)
31.6 (10.8, 43.3)
29.6 (17.6, 43.5)
0.988
Cross sections with a ratio of uncovered to total struts [0.3 (%)
0 (0, 5.3)
0 (0, 8.5)
0.279
Maximum length of segments with uncovered struts (mm)
1.0 (0.2, 2.0)
1.0 (0.2, 2.9)
0.390
Percentage of malapposed struts
0 (0, 0.8)
0 (0, 1.2)
0.332
Change of percentage of malapposed struts from baseline to 3 months
1.3 ± 2.7
2.3 ± 2.9
0.102
Cross sections with any malapposed struts (%)
0 (0, 4.2)
0 (0, 6.4)
0.341
Total malapposed volume (mm3)
0 (0, 3.1)
0 (0, 10.8)
0.106
Maximum malapposed CSA (mm2)
0 (0, 0.3)
0 (0, 0.6)
0.138
Maximum malapposed distance (lm)
0 (0, 117.5)
0 (0, 0.2)
0.242
Uncovered struts analyses
Malapposition analyses
Types of stent malapposition, n (%)
0.488
Persistent, n (%)
11 (23)
16 (35)
Resolved, n (%)
22 (46)
21 (46)
Late acquired, n (%)
2 (4)
1 (2)
Values are presented as n (%), mean ± SD, or median (interquartile range) PtCr-EES platinum–chromium everolimus-eluting stent, CoCr-EES cobalt–chromium everolimus-eluting stent, CSA cross-sectional area, NIH neointimal hyperplasia
Int J Cardiovasc Imaging
Fig. 3 Association between the percentage of malapposed struts immediately post-procedure versus the percentage of uncovered struts (a) and the percentage of malapposed struts (b) at the 3-month follow-up
clinical studies as determined with OCT as well as comparable angiographic and clinical outcomes with the CoCrEES [6–9]. The PtCr-EES provides excellent deliverability, conformability, radiopacity, and radial strength with compression resistance [4, 6–9]. In particular, the material properties of platinum chromium, together with the design of the PtCr-EES, are expected to provide a superior capacity against stent recoil compared to current cobalt chromium alloy stent platforms such as CoCr-EES. Using a bench test, the recoil of the PtCr-EES is less than that of the CoCr-EES; 3.6 % for PtCr-EES versus 4.6 % for CoCrEES [9, 21]. Due to these characteristics of the PtCr-EES, this stent seems to provide better stent apposition and decrease post-procedural stent malapposition. However, only a few studies have produced randomized data regarding serial OCT evaluation of stent apposition from nominal pressure and immediately post-procedure to the early follow-up period. Prior studies investigating these issues were registry based or evaluated stent expansion using intravascular ultrasound [5, 7, 22]. In one intravascular ultrasound study [13], the rate of incomplete stent apposition at post-procedure with PtCr-EES (n = 88) was 5.7 %, which was lower than that of the CoCr-EES in previous studies [1, 7]. In a recent single-center, non-randomized OCT study (n = 42), acute responses to the PtCror CoCr-EES were similar with concentric expansion and a comparable incidence of stent malapposition between the two DESs [15]. Compared to the previous study [15], this study was randomized and evaluated serial OCT findings (particularly, at nominal pressure and immediately postprocedure). In the present study, although the primary endpoint, the percentage of malapposed struts, did not achieve statistical significance, the PtCr-EES showed a
better apposition on the other various OCT-measured stent malapposition parameters immediately after stent deployment with nominal pressure. Immediately post-procedural OCT after adjunctive post-dilation (all patients underwent adjunctive post-dilation) showed that the PtCr-EES produced a significantly lower percentage of cross sections with malapposed struts and a lower maximum malapposed strut distance. Acute stent malapposition detected with OCT is frequently observed and is resolved or persistent according to the degree of stent malapposition [17, 23]. Until now, there have been no established data regarding the impact of acute stent malapposition on the strut coverage at follow-up. This study showed a significant correlation between post-procedural stent apposition and 3-month follow-up strut coverage; these findings suggested that strut coverage on OCT in early follow-up periods after DES implantation could be improved by assessing stent apposition with OCT at the time of percutaneous coronary intervention. In lesions with greater amounts of acute stent malapposition, stent malapposition persisted without resolution and longer duration of dual antiplatelet treatment with potentially increased risk of bleeding might be subsequently required to prevent the occurrence of future adverse cardiac events [17, 24]. In a non-randomized study comparing clinical outcomes of percutaneous coronary intervention using angiographic guidance alone versus angiographic plus OCT guidance, angiographic plus OCT guidance was associated with a significant reduction in cardiac death or myocardial infarction [25]. Favorable clinical outcomes in patients with OCT-guided percutaneous coronary intervention may be partly explained by achieving superior strut coverage by reducing incomplete stent apposition with intra-procedural
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OCT. These relationships could be applied to the determination for the optimal duration of dual antiplatelet therapy after DES implantation. A future study investigating the relationship between the strut coverage at early period and the determination of dual antiplatelet therapy and its resultant clinical outcomes will be needed. The current study has some limitations. First, there was no specific strategy for pre-ballooning and high-pressure post-dilation in this study. In addition, although we found no significant differences in post-dilation strategies between the two DES groups, no standard criteria for OCTguided percutaneous coronary intervention have been established. Second, different nominal pressure in each DES may affect the OCT findings after stent deployment with nominal pressure. However, maximal inflation pressure immediately post-procedure was similar between the two groups. Third, there were no analyses comparing longitudinal foreshortening. Because recent publications have suggested that PtCr-EES could be more prone to longitudinal deformation than other platforms, there would be need for the randomized comparison in the real practices [26, 27]. Finally, the future study investigating the clinical implication for the difference of the ratio or incidence of malapposition between two DESs and the relation between malapposed and uncovered struts will be needed. In conclusion, this randomized study showed that acute stent malapposition was less frequently observed in PtCrEES-treated patients than in CoCr-EES-treated patients. Acknowledgments This study was supported by a grant from the Korea Healthcare Technology R&D Project, Ministry for Health, Welfare and Family Affairs, Republic of Korea (Nos. A085012, A102064), a grant from the Korea Health 21 R&D Project, Ministry of Health and Welfare, Republic of Korea (No. A085136), and the Cardiovascular Research Center, Seoul, Korea. Conflict of interest
4.
5.
6.
7.
8.
9.
10.
None. 11.
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