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Original Contribution

Clinical and Biomechanical Behavior of a Platinum-Chromium Stent Platform in a Large All-Comer Single-Center Population: Insights From the Novara-PROMETEUS Registry

Alessandro Lupi, MD1; Italo Porto, MD, PhD2; Andrea Rognoni, MD1; Maurizio Lazzero, MD1;Rossella Fattori, MD3; Rosario Parisi, MD3; Giovanni Luigi De Maria4; Angelo Sante Bongo, MD1;Imad Sheiban, MD5; Leonardo Bolognese, MD2; Pierfrancesco Agostoni, MD, PhD6; Gioel Gabrio Secco, MD3,7; for the Novara-PROMETEUS (Platinum ChROMium Everolimus EluTing StEnt SpontaneoUs RegiStry)Investigators

ABSTRACT: Aims. Longitudinal deformation has been described as a new complication affecting new-generation thin-strut coronary stents. Benchmark tests have suggested that the platinum-chromium (PtCr) Element coronary stent platform (Boston Scientific) might present increased susceptibility to this complication. Our study as-sessed the incidence of longitudinal stent deformation in a large sin-gle-center study population. Methods and Results. A total of 337 consecutive Promus Element PtCr stents deployed in an all-comer population underwent quantitative coronary angiography (QCA) analysis. Postdeployment QCA measured/nominal stent length ratio (SLR) was considered as a surrogate estimate of longitudinal stent de-formation and averaged 0.95 ± 0.04 in the entire population. This small postdeployment reduction of stent length had no clinical rele-vance, leading to 3 cases (0.9%) of trivial geographical miss, which did not require further interventions. Plaque prolapse through the stent struts was observed in 19 cases (5.6%). Only 1 case of typical “concer-tina” effect (0.3%) complicated an ostial stenosis treatment requiring deployment of a second stent, while in 3 cases (0.9%), stent struts adapted to severely tortuous and calcified vessels mimicked longitudi-nal stent deformation, without further complications. Multiple regres-sion analysis demonstrated a significant correlation between need for predilation and lower SLR values, while postdilation independently predicted higher SLR. Conclusions. Systematic QCA analysis of a large single-center all-comers PCI population treated with PtCr stents failed to detect any clinically relevant longitudinal stent deformation. Complex lesions needing predilation were associated with a reduced SLR; conversely, postdilation was associated with QCA stent measures close to nominal. Clinicaltrials.gov ID: NCT01759719.

J INVASIVE CARDIOL 2014;26(7):311-317

Key words: longitudinal stent deformation, stent,platinum/chromium, coronary angioplasty

In the last years, the need to deal with increasingly com-plex coronary anatomy has polarized the effort of biomedical research toward improvement of stent crossing profile, con-formability, and x-ray opacity.1 In particular, longitudinal con-nectors between stent cells and strut thickness have been the main targets of stent engineering, as they profoundly affect stent longitudinal flexibility and deliverability, as well as vessel conformability and cell characteristics after deployment.2 Stent materials have also changed, with the introduction of high-tech alloys like Cobalt/Chromium (CoCr) or Platinum/Chromium (PtCr),3,4 allowing further miniaturization of stent struts with-out compromising radial strength.

Overall performance of stents, however, basically depends on a trade-off between crossing profile and flexibility and radial and longitudinal forces exerted after deployment.5 Newer-gen-eration stents have been characterized by important improve-ments in strut thinning and flexibility while maintaining radial strength, and yet the very low metal density per mm3 of stent volume has eventually put the issue of longitudinal strength in the spotlight.6,7

Among the latest developed stent platforms, the PtCr Ele-ment (Boston Scientific) has demonstrated good overall clini-cal results in the PERSEUS and PLATINUM programs.8-11

However, several reports12-26 recently suggested the suscepti-bility of this platform to an excessive longitudinal deforma-tion during or following stent deployment, compared to other stent designs.27

Published material about this phenomenon, however, is mainly limited to case reports/case series17-25 or bench testing studies,26-28 while only a few retrospective clinical registries have systematically explored a patient cohort14-16 and only one has employed quantitative coronary angiography (QCA) to accu-rately test deployed stent dimensions.14

We prospectively designed the Novara-PROMETEUS (Novara Platinum CROMium Everolimus EluTing StEnt SpontaneoUs RegiStry), Clinicaltrials.gov ID: NCT01759719, with the purpose of analyzing both the incidence as well as factors associated with longitudinal stent deformation in an all-comer population treated by the new generation of PtCr Promus Element stent.

From the 1Cardiology Department, Maggiore della Carità Hospital, Novara, Italy; 2Cardiology Department, San Donato Hospital, Arezzo, Italy; 3Division of Inter-ventional Cardiology, Ospedali Riuniti Marche Nord, Pesaro, Italy; 4Cardiovascular Medicine Department, Catholic Unversity of the Sacred Heart, Rome, Italy; 5Interven-tional Cardiology, Division of Cardiology, University of Turin, Turin, Italy; 6Univer-sity Medical Center Utrecht, Utrecht, The Netherlands; and 7Department of Clinical and Experimental Medicine, University of Eastern Piedmont, “Maggiore della Carità” Hospital, Novara, Italy.

Disclosure: The authors have completed and returned the ICMJE Form for Dis-closure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Manuscript submitted October 7, 2013, provisional acceptance given January 9, 2014, final version accepted January 29, 2014.

Address for correspondence: Dr Alessandro Lupi, Cardiologia ospedaliera, Ospedale Maggiore della Carità, Cso Mazzini 18, 28100 Novara, Italy. Email: lupialessandro1@tin.it

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MethodsDevice description. The PtCr Element bare-metal stent

platform is laser cut from a tube of platinum chromium alloy with an offset peak-to-peak design and two links connecting adjacent rings,28 with a stent strut thickness of 81-86 µm ac-cording to the nominal caliber. The PtCr Promus Element is an everolimus-eluting stent based on the Element stent platform in which the antiproliferative agent everolimus (100 µg/cm2) is applied in a biocompatible acrylic polymer and fluorinated copolymer.29,30 Stent strut thickness is 81 to 86 µm of the stent struts plus 14 to 18 µm of the polymeric coverage.

Patient population. Novara-PROMETEUS is a single-cen-ter registry enrolling unselected patients undergoing PCI with a Promus Element.

Inclusion criteria were: (1) treatment with percutaneous coronary intervention and at least one Promus Element stent implantation; and (2) availability of high-quality coronary an-giographic documentation in the same projection of the base-line lesion and the final result with the deployed stent.

The only exclusion criterion was an angiographic documenta-tion deemed unsuitable for QCA analysis (lack of baseline and final angiography of the treated segment in the same projection, excessive foreshortening, insufficient contrast to detect stent edg-es, lack of guiding catheter for appropriate calibration).

Qualitative coronary angiography evaluation. Qualitative inspection of all the angiograms was performed by 2 indepen-dent expert reviewers (AL and AR). The presence of obvious stent shortening or stent elongation due to stent struts being pushed together or pulled apart (“concertina” effect), other minor stent deformations, intrastent plaque prolapse, and geo-graphical miss were recorded. For this visual assessment, lon-gitudinal compression/elongation was defined as inconsistency in the radiodensity pattern along the length of the stent, or other gross irregularities or deformities determining distortion or shortening of a stent in the longitudinal axis following suc-cessful stent deployment.13 Geographic miss was defined when the deployed stent could not fully cover the entire length of the diseased or injured segment.31 Divergent opinions were re-solved by consensus.

Quantitative coronary angiography (QCA). As routine in our center, standard image acquisition of the treated stenosis was performed using two or more angiographic projections, intra-coronary nitroglycerin to provide maximum coronary dilation, and repetition of identical angiographic projections of the lesion at baseline and final angiography. Angiograms were analyzed on site by two independent reviewers (AL and DDV). Using the contrast-filled injection catheter as the calibration source, quan-titative angiographic analysis was performed using a validated automated edge detection algorithm (QAngio XA; Medis).32 The best angiographic projection that minimized stent foreshorten-ing and vessel overlap was used for analysis. Lesion length, de-fined as the distance from the proximal to the distal shoulder of the lesion, minimal lumen diameter (MLD), and percentage of diameter stenosis at the site of stent placement were evaluated for each lesion before and after the coronary intervention.

For each stent, final length measured by QCA was com-pared to the nominal stent length (stent length ratio; SLR). A

ratio of 1.0 would indicate equivalent measured and nominal stent lengths. In cases of overlapping stents, only the first de-ployed stent was considered for the length analysis. The excel-lent radiopacity of the Promus Element stent allowed precise QCA sizing with clear identification of the overlapping zones.

Three-dimensional quantitative coronary angiography (3D-QCA). A 10% random sample from the study stent pool underwent 3D-QCA evaluation according to a validated pro-tocol.33 Available angiographic projections targeting the stent at the end of each procedure were analyzed by two interven-tional cardiologists (GLDM and IP) blinded to clinical data. Two electrocardiographically gated end-diastolic frames in two unmagnified views (one in each view) separated from each other by at least 30° (in either lateral or cranio-caudal planes) were selected. In each single biplane image set, two clearly identifiable reference points corresponding to proximal and distal stent edges were defined. Three-dimensional recon-struction of the stented coronary artery segment was obtained by CAAS QCA-3D system (Pie Medical Imaging BV), start-ing from the selected set of biplane angiographic images. After indicating a so-called “common image” point, which should be unambiguously visible in both projections, a path through the lumen covering the segment to be analyzed was desig-nated. The luminal borders on both projections were found by automatic contour detection and manually corrected when required. The software then automatically generated a three-dimensional representation of the arterial lumen, giving a measure of the stented segment length.

Evaluation of outliers. Finally, a third expert interventional cardiologist (ASB) performed a blinded reexamination of the angiograms corresponding to the 20 lowest and highest ratios to identify any case of even mild stent deformation.

Statistical methods and ethical issues. Categorical data were presented as counts and percentages and compared by χ2 test. Continuous data with normal distribution were expressed as mean ± standard deviation (SD) and compared by t-test. Non-normally distributed data were expressed as median and interquartile range and compared by Wilcoxon signed rank sum test. To test whether a significant change occurred in re-peated measurements of QCA data before and after interven-tion, ANOVA followed by Newman Keuls test for repeated measurements was used. When data did not fit normal distri-bution, they were compared by Kruskal-Wallis test. Correlation between QCA and 3D-QCA was assessed with the Pearson’s correlation coefficient.

Multiple regression analysis was performed to determine independent predictors of Pt/Cr QCA SLR. The covari-ates tested in this model were male sex, age, hypertension, diabetes, dyslipidemia, body mass index (BMI) >30 kg/m2 of body surface area (BSA), estimated glomerular filtration rate (eGFR) <30 mL/min, cigarette smoking (active or quit <2 years prior), previous myocardial infarction (MI) and/or PCI, previous coronary artery bypass graft, peripheral ar-tery disease, multivessel CAD, left main, type B2/C lesion, multivessel PCI, need for predilation, high-pressure postdila-tion, number of implanted stents, total stent length (mm), presence of thrombus, ostial lesions, tortuous lesions, lesions

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longer than 20 mm, bifurcations, severely calcified lesions, chronic total occlusion (CTO) lesions, kissing balloon dila-tions, maximum inflation pressure (atm), deep intubation with guiding catheter, use of intravascular ultrasound (IVUS), use of thrombectomy catheters, use of Rotablator (Boston Scientific), and use of distal filters.

Univariate predictors that achieved a P-value <.10 were included en bloc in the multivariate model. All statistical tests were 2-tailed and a P-value <.05 was considered statistically sig-nificant. The investigation conforms to the principles outlined in the Declaration of Helsinki.34 All patients provided written informed consent. The study protocol was approved by the in-stitutional review board of the “Maggiore della Carità” Univer-sity Hospital and is registered at http://www.clinicaltrials.gov (NCT01759719).

ResultsThis analysis included 337 PtCr stents deployed in 253

consecutive all-comer patients treated in our laboratory from January 2011 to August 2012 (Figure 1). Clinical and inter-ventional characteristics are summarized in Table 1. A mod-erate-to-high general profile of risk could be observed, with a significant prevalence of diabetes, peripheral artery disease, multivessel atheroma, and left main disease. Most interventions were performed transradially, with an average of 1.33 Promus Element stent deployed per patient.

Lesion characteristics are summarized in Table 2. Most of the 286 treated lesions showed a high degree of complexity. About 15% of the lesions were ostial, and two-thirds were longer than 20 mm. True bifurcational disease was also well represented. As a result of such complexity, there was a relatively frequent use of IVUS and thrombectomy catheters (about 1 in 10).

Measurement of QCA stent length: stent length ratio. Stent length ratio averaged 0.95 ± 0.04 in the whole popula-tion, with maximum and minimum values of 1.07 and 0.73, respectively (Figure 2). The cumulative distribution curves of SLR showed similar ratios according to various stent diameters and lengths (Figure 3).

The small postdeployment reduction of stent length had no clinical relevance, with only 3 cases (0.9%) of small geographi-cal miss, which did not require further intervention. Only 1 clear case of concertina effect was observed (0.3%) (Figure 4), requiring a second stent implantation, while in 3 cases (0.9%) close fitting of the stent struts to very tortuous and calcified lesions mimicked longitudinal stent deformation (“pseudocon-certina” effect).

Blinded reexamination of the angiograms corresponding to the 20 lowest and highest SLRs did not identify any cases of stent deformation. These extreme measured-to-nominal ratios appeared to result from inherent QCA variability, out-of-plane magnification from the calibration source, and foreshortened projections.

Measurement of 3D-QCA stent length: stent length ratio. Of the 337 stents evaluated with QCA, a total of 34 stents (10.0%) underwent 3D-QCA analysis. The clinical and angiographic characteristics of this sample were similar to the whole population of the study. Measured nominal SLRs

Figure 1. Flow chart describing the enrollment and exclusion processes in the Novara-Prometeus Registry.

Table 1. Demographic and clinical characteristics of the study population.

Age (years) 66.2 ± 10.5

Male sex 188 (74.0%)

Stable coronary artery disease 171 (67.3%)

Unstable angina/non-ST elevation MI 48 (19.0%)

ST-elevation MI 33 (13.0%)

Radial route 176 (69.3%)

Femoral route 76 (30.0%)

Mean number of treated vessels/patient 1.18

Total number of treated vessels 301

Mean number of stents per patient 1.33

Total number of stents 337

Clinical characteristics

Hypertension 176 (69.3%)

Dyslipidemia 131 (51.6%)

Diabetes 105 (41.3%)

Tobacco (>6 cigarettes/day, active or quit <2 years) 69 (27.2%)

Peripheral artery disease 43 (16.9%)

Chronic kidney failure (eGFR <30 cc/min) 20 (7.9%)

Previous MI/PCI 124 (48.8%)

Previous CABG 41 (16.1%)

Left main CAD 38 (15.0%)

Multivessel CAD 166 (65.4%)

Data given as mean ± standard deviation, number (percentage), or number.

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obtained through the 3D-QCA analysis aver-aged 0.95± 0.09, with maximum and minimum values of 1.11 and 0.74, respectively. 3D-QCA measurements significantly correlated to standard QCA measures (r=0.63; P<.001).

Multiple regression analysis. Multiple regres-sion analysis was performed to identify indepen-dent predictors of SLR in the registry population. Need for predilation was associated with lower SLR values, while postdilation predicted higher final SLR (Table 3) in both univariate and multi-variate analyses.

DiscussionThe main result of our all-comer registry of pa-

tients treated with a Pt/Cr Promus Element stent is that severe longitudinal stent deformation is an extremely rare phenomenon. In the sample eval-uated in our study, SLR, a surrogate marker for longitudinal stent deformation, was substantially similar to those previously reported in literature.14 Of note, the anatomical complexity of the popu-lation of our study far exceeded that of the cur-rently available randomized controlled trials,8,10,11 increasing the practical value of our observation. Interestingly, the small differences recorded in our study between nominal and postdeployment lon-gitudinal stent dimensions did not translate into a significant increase in geographical miss requiring unplanned interventions.

These results, obtained with standard QCA, were corroborated by 3D-QCA analysis, confirm-ing measured to nominal SLRs similar to the main analysis. Of note, 3D-QCA is considered the best approximation for measuring stent length in vivo.35

Finally, we observed that the need for predila-tion was an independent predictor of a lower SLR, possibly as a proxy for lesion complexity. Further-more, postdilation was demonstrated to be inde-pendently associated with higher final SLR.

Longitudinal deformation: a “necessary” de-fect of modern stents? Modern coronary stents have made it possible to treat extreme cases of cor-onary obstructive disease without resorting to sur-gery. However, the task to face complex coronary anatomy has prompted biomechanical researchers to maximally improve stent properties such as pro-file, conformability, cell design, and x-ray opacity.1 Longitudinal connectors and strut thickness have been the preferred target of stent engineering,7 as they profoundly condition stent longitudinal flex-ibility and deliverability before deployment, as well as stent conformability to vessel and cell size and shape after deployment. Stent materials have also significantly changed with the introduction of high-tech alloys like Co/Cr or Pt/Cr, with further reduction of stent strut thickness.3 Performance of

Table 2. Characteristics of treated lesions and implanted stents in the study population.

Stable coronary artery disease 232 (68.8%)

Unstable angina/non-ST elevation myocardial infarction 60 (17.8%)

ST-elevation myocardial infarction 45 (13.4%)

AHA/ACC lesion classification A 18 (6.3%)

AHA/ACC lesion classification B1 51 (17.8%)

AHA/ACC lesion classification B2 69 (24.1%)

AHA/ACC lesion classification C 148 (51.7%)

AHA/ACC lesion classification B2/C 217 (75.9%)

Left main coronary artery disease 41 (14.3%)

Multivessel coronary artery disease 193 (67.5%)

Vessel treated

Left main 18 (6.3%)

Left anterior descending 101 (35.3%)

Left circumflex 57 (19.9%)

Right coronary artery 69 (24.1%)

Diagonal/obtuse marginal/left posterior descending 42 (14.7%)

Saphenous vein graft 20 (7.0%)

Lesion characteristics

Thrombus 51 (17.8%)

Ostial 41 (14.3%)

Tortuous 92 (32.2%)

Long (>20 mm) 188 (65.7%)

Bifurcation 106 (37.1%)

Severe calcium 107 (37.4%)

Chronic total occlusion 13 (4.5%)

Percutaneous coronary intervention details

Predilation 148 (51.7%)

Postdilation 215 (75.2%)

Kissing balloon 31 (10.8%)

Intravascular ultrasound 39 (11.6%)

Rotablator 5 (1.5%)

Maximum inflation pressure (atm) 20.80 ± 3.43

Deep intubation 36 (12.6%)

Thrombectomy catheter 37 (11.0%)

Filter systems 15 (4.5%)

Quantitative coronary angiography analysis

Reference diameter (mm) 2.89 ± 0.53

Minimum luminal diameter (mm) 0.75 ± 0.39

Lesion length (mm) 21.84 ± 10.38

Nominal stent diameter (mm) 2.96 ± 0.50

Nominal stent length (mm) 21.39 ± 5.49

Stent length after deployment (mm) 20.51 ± 5.33

Nominal/postdeployment ratio 0.95 ± 0.04

Final minimal luminal diameter (mm) 2.50 ± 0.40

Final mean luminal diameter (mm) 2.93 ± 0.40

“Concertina” effect 1 (0.03%)

“Pseudoconcertina” effect 3 (1.05%)

Data given as mean ± standard deviation, number (percentage), or number.

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stents, however, ultimately depends on a trade-off between low crossing profile and flexibility on one side, and the radial and longitudinal forces exerted by the expanded stent on the other.5 Thus, while new-generation stents have reached excellent deliv-erability, concerns about the radial strength of the scaffolding offered to the vessel wall have developed.

Manufacturers have meticulously addressed the problem of radial strength, which is generally maintained despite the re-duction of metal density,6 and yet data about stent longitudinal strength (eg, resistance to compressing or elongating forces) is seldom found in the technical documentation of novel stents.

Longitudinal stent deformation: real-world occurrence versus selection bias. Reports of longitudinal stent defor-mation, consisting generally of stent shortening and elonga-tion,13,15 were thus somewhat expected, as it is conceivable that the combination of fewer connectors and thinner struts may have adversely affected stent longitudinal integrity. Stent dis-tortion has usually occurred after deployment, but also dur-ing positioning, high-pressure postdilation, or withdrawal in the guiding catheter.13,17,18,36,37 Recently, benchmark evaluation comparing the four most diffuse stent design families associated stent susceptibility to longitudinal compression with stent de-sign, particularly to the two-link offset peak-to-peak design.28

In contrast with these data, a pooled analysis from the PER-SEUS and PLATINUM randomized controlled studies involving more than 2400 stents has demonstrated only a modest length reduction after deployment.14 The analysis by Kereiakes et al, how-ever, suffers from the limitations of most randomized trials, com-prising mainly moderate-risk patients and low-to-medium lesion complexity. In particular, their sample included 25% diabetics, 21% American College of Cardiology/American Heart Associa-tion (ACC/AHA) type-C lesions, 25% calcified lesions, 3% tortu-ous lesions, and mean lesion length of 14 mm, which are charac-teristics not representative of a real-world population. Moreover, in this selected population, postdilation was used in only 50% of lesions with a mean pressure of 16 atm, ST-elevation MI was ex-cluded, while no data about IVUS and filters were reported.

Figure 2. Picture showing mean and individual values of nominal and quantitative coronary angiography postdeployment stent length.

Figure 3. Picture showing the distribution in the study population of the quantitative coronary angiography/nominal stent length ratio.

Figure 4. (A) Promus Element stent is deployed across an ostial lesion of the right coronary artery (RCA). (B) After various attempts to advance another stent distally in the RCA, clear longitudinal shortening and deformation of the previously deployed Promus Element stent is observed. (C) After postdilation, incomplete recovery of the original stent length is obtained.

P<.001

Nominal Stent Length

QCA/Nominal Length Ratio

Ste

nt L

eng

th (m

m)

Per

cent

ile

Post-Deployment Stent Length

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Novara-PROMETEUS adds to and extends Kereiakes’s data. In our cohort, 41.7% had diabetes was, 51.7% had ACC/AHA type-C lesions, 37% had calcified lesion, mean le-sion length was 21 mm, and ST-elevation MIs were included. Of note, a significant proportion of patients were treated with bulky devices, such as IVUS (11.6%), aspiration thrombec-tomy (11.0%), and filters (4.5%), which have been previously addressed as potential causes of stent deformation or fracture.13 Also, postdilation was very frequent (two-thirds of patients), and performed with very high pressures (>20 atm on average). A significant fraction of patients also required deep intubation, with the guiding catheter passing through the deployed Pt/Cr stent, to increase back-up for distal stent passage. That longi-tudinal stent deformation remains a rare phenomenon in this all-comer real-world population, without a clear clinical effect, is quite reassuring.

Risk factors for longitudinal deformation. It is notewor-thy that of the cited potential risk factors for stent deformation, none except lesion length correlated to SLR when considered singularly. Multiple regression analysis identified only the need for predilation as an independent predictor of low SLR, while postdilation was significantly and independently correlated with a reduced longitudinal deformation. The most reasonable ex-planation for our findings is that both variables acted as proxies for lesion complexity, linked to higher risk of incomplete stent expansion and consequently to stent deformation. A causative effect for the absence of postdilatation, however, cannot be ful-ly excluded, supporting our practice of an (almost) systematic postdilatation of implanted stents with non-compliant balloons.

Study limitations. First, we are aware that using angiog-raphy has limitations in the evaluation of stent deformation. Indeed, the longitudinal stent deformation definition is based on a pattern of dense or overlapping stent struts, and the ratio of measured/nominal stent length can only be considered a surrogate marker of inappropriate stent expansion over the

longitudinal plane. Longitudinal stent deformation may oc-cur without significant change in stent length and may be detectable only by IVUS.18 It must be noted, however, that in our study both visual evaluation of stent strut deformity and QCA analysis were performed, with evidence of a very low rate of longitudinal stent deformation, similar to previously published data.14 Moreover, the subanalysis using 3D-QCA is in full agreement with the main results.

Furthermore, QCA was performed by trained personnel (at least a decade of experience in QCA) at the core lab of our in-stitution, and not by an independent core lab.

Finally, our analyses could have been affected by the typical biases affecting QCA studies,32 and mainly depending on an-giographic angulations, leading to foreshortening and resulting in low SLRs. However, to minimize bias, only patients who had at least 3 cine loops (baseline, after stent deployment and after postdilation) in the same angiographic projection were includ-ed in the analysis. Moreover, the independent confirmation by 3D-QCA, known to significantly reduce two-dimensional bi-ases,38 is reassuring.

ConclusionOur study demonstrates that longitudinal stent deforma-

tion, a recently recognized complication of coronary stent deployment, is rare in an all-comer population treated with PtCr stents at a large tertiary center. Multivariate analysis confirmed the importance of lesion complexity for longitu-dinal deformation.

References1. Garg S, Serruys PW. Coronary stents: looking forward. J Am Coll Cardiol. 2010;56(10

Suppl):S43-S78.2. Ormiston JA, Dixon SR, Webster MW et al. Stent longitudinal flexibility: a compari-

son of 13 stent designs before and after balloon expansion. Catheter Cardiovasc Interv. 2000;50(1):120-124.

3. O’Brien BJ, Stinson JS, Larsen SR, Eppihimer MJ, Carroll WM. A platinum-chromi-um steel for cardiovascular stents. Biomaterials. 2010;31(14):3755-3761.

Table 3. Predictors of quantitative coronary angiography/nominal stent length ratio according to multiple regression analysis.

Independent Variable

Regression Coefficient

Standard Error

Lower 95.0% CL

Upper 95.0% CL

Standardized Coefficient

P-Value

Ostial lesion -0.0069 0.0078 -0.0223 0.0084 -0.0666 .37

Tortuous vessel 0.0009 0.0048 -0.0085 0.0103 0.0117 .85

Visible calcium 0.0026 0.005 -0.0072 0.0124 0.0344 .60

Bifurcation -0.0063 0.0052 -0.0165 0.0039 -0.0836 .22

Reference diameter 0.0044 0.0043 -0.004 0.0129 0.066 .30

Lesion length 0.0005 0.0002 0.0001 0.0009 0.1325 .06

Deep intubation 0.0041 0.0083 -0.0122 0.0203 0.037 .62

Kissing balloon -0.0008 0.0082 -0.0169 0.0154 -0.0067 .92

Postdilation 0.0162 0.0066 0.0033 0.0292 0.1917 .01

Predilation -0.0146 0.0047 -0.0239 -0.0053 -0.1991 .01

Dilation pressure -0.0005 0.0009 -0.0021 0.0012 -0.0439 .58

DF R2 Sum of Squares Mean Square F-Ratio P-Value

Model 11 0.077 0.0296 0.0026 2.089 .02

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4. Menown IB, Noad R, Garcia EJ, Meredith I. The platinum chromium element stent platform: from alloy, to design, to clinical practice. Adv Ther. 2010;27(3):129-41.

5. Hoffmann R, Mintz GS, Haager PK, et al. Relation of stent design and stent surface material to subsequent in-stent intimal hyperplasia in coronary arteries determined by intravascular ultrasound. Am J Cardiol. 2002;89(12):1360-1364.

6. Foin N, Di Mario C, Francis DP, Davies JE. Stent flexibility versus concertina effect: Mechanism of an unpleasant trade-off in stent design and its implications for stent selection in the cath-lab. Int J Cardiol. 2013;164(3):259-261.

7. Mortier P, De Beule M. Stent design back in the picture: an engineering perspective on longitudinal stent compression. EuroIntervention. 2011;7(7):773, 775.

8. Kereiakes DJ, Cannon LA, Feldman RL, et al. Clinical and angiographic outcomes after treatment of de novo coronary stenoses with a novel platinum chromium thin-strut stent: primary results of the PERSEUS (Prospective Evaluation in a Randomized Trial of the Safety and Efficacy of the Use of the TAXUS Element Paclitaxel-Eluting Coronary Stent System) trial. J Am Coll Cardiol. 2010;56(4):264-271.

9. Cannon LA, Kereiakes DJ, Mann T, et al. A prospective evaluation of the safety and efficacy of TAXUS Element paclitaxel-eluting coronary stent implantation for the treatment of de novo coronary artery lesions in small vessels: the PERSEUS Small Vessel trial. EuroIntervention. 2011;6(8):920-927, 1-2.

10. Meredith IT, Whitbourn R, Scott D, et al. PLATINUM QCA: a prospective, multi-centre study assessing clinical, angiographic, and intravascular ultrasound outcomes with the novel platinum chromium thin-strut PROMUS Element everolimus-eluting stent in de novo coronary stenoses. EuroIntervention. 2011;7(1):84-90.

11. Stone GW, Teirstein PS, Meredith IT, et al. A prospective, randomized evaluation of a novel everolimus-eluting coronary stent: the PLATINUM (a Prospective, Random-ized, Multicenter Trial to Assess an Everolimus-Eluting Coronary Stent System [PRO-MUS Element] for the Treatment of Up to Two de Novo Coronary Artery Lesions) trial. J Am Coll Cardiol. 2011;57(16):1700-1708.

12. Janakiraman E, Subban V, Victor SM, Mullasari AS. Longitudinal deformation — price we pay for better deliverability of coronary stent platforms. Indian Heart J. 2012;64(5):518-520.

13. Williams PD, Mamas MA, Morgan KP, et al. Longitudinal stent deformation: a retro-spective analysis of frequency and mechanisms. EuroIntervention. 2012;8(2):267-274.

14. Kereiakes DJ, Popma JJ, Cannon LA et al. Longitudinal stent deformation: quantita-tive coronary angiographic analysis from the PERSEUS and PLATINUM randomised controlled clinical trials. EuroIntervention. 2012;8(2):187-195.

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