Author + information
- Received January 25, 2011
- Revision received March 29, 2011
- Accepted April 11, 2011
- Published online July 1, 2011.
- Josep Gomez-Lara, MD⁎,
- Salvatore Brugaletta, MD⁎,
- Vasim Farooq, MBChB⁎,
- Robert Jan van Geuns, MD, PhD⁎,
- Bernard De Bruyne, MD, PhD†,
- Stephan Windecker, MD‡,
- Dougal McClean, MD§,
- Leif Thuesen, MD∥,
- Dariusz Dudek, MD¶,
- Jacques Koolen, MD, PhD#,
- Robert Whitbourn, MD⁎⁎,
- Pieter C. Smits, MD, PhD††,
- Bernard Chevalier, MD‡‡,
- Marie-Angèle Morel, BSc§§,
- Cécile Dorange, MSc∥∥,
- Susan Veldhof, RN∥∥,
- Richard Rapoza, PhD¶¶,
- Hector M. Garcia-Garcia, MD, PhD⁎,§§,
- John A. Ormiston, MBChB, PhD## and
- Patrick W. Serruys, MD, PhD⁎,⁎ ()
- ↵⁎Reprint requests and correspondence:
Dr. Patrick W. Serruys, Department of Interventional Cardiology, Thoraxcenter, Erasmus MC, ‘s-Gravendijkwal 230, 3015 CE, Rotterdam, the Netherlands
Objectives The aim of this study was to compare the angiographic changes in coronary geometry of the bioresorbable vascular scaffolds (BVS) and metallic platform stent (MPS) between baseline and follow-up.
Background Coronary geometry changes after stenting might result in wall shear stress changes and adverse events. The BVS have better conformability, compared with MPS, but still modify artery geometry. It is uncertain whether the BVS resorption can restore the coronary anatomical configuration at midterm follow-up.
Methods All patients of the ABSORB (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System [BVS EECSS] in the Treatment of Patients With de Novo Native Coronary Artery Lesions) and SPIRIT (A Clinical Evaluation of the XIENCE V Everolimus Eluting Coronary Stent System in the Treatment of Patients With de Novo Native Coronary Artery Lesions) trials treated with a single 3.0 × 18 mm device and imaged at baseline and 6- to 12-month follow-up were eligible. Coronary geometry changes were assessed with quantitative angiography as changes in curvature and angulation. Curvature and angulation changes between systole and diastole were investigated to assess hinging movements of the coronary artery.
Results One hundred sixty-one patients (86 BVS, and 75 MPS) were included. Baseline angiographic characteristics were similar. From post-implantation to follow-up, curvature increased 8.4% (p < 0.01) with BVS and decreased 1.9% (p = 0.54) with MPS; p = 0.01. Angulation increased 11.3% with BVS (p < 0.01) and 3.8% with MPS (p = 0.01); p < 0.01. From pre-implantation to follow-up, BVS decreased 3.4% the artery curvature (p = 0.05) and 3.9% the artery angulation (p = 0.16), whereas MPS presented with 26.1% decrease in curvature (p < 0.01) and 26.9% decrease in angulation (p < 0.01), being larger with MPS (p < 0.01, both). Hinging movements in curvature from pre-implantation to follow-up decreased 19.7% with BVS and 39.0% with MPS (p = 0.27) and decreased 3.9% with BVS and 26.9% with MPS in angulation (p < 0.01).
Conclusions At midterm follow-up, the BVS tended to restore the coronary configuration and the systo-diastolic movements to those seen before implantation. The coronary geometry remained similar to that seen at after implantation with MPS. (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System [BVS EECSS] in the Treatment of Patients With de Novo Native Coronary Artery Lesions; NCT00856856)
Coronary geometry is the major determinant of the shear stress inflicted on the endothelial cells lining the artery wall. Physiological wall shear stress (WSS) induces the alignment of the endothelial cells in the flow direction and the secretion of numerous antiatherogenic substances such as endothelin and nitric oxide. In contrast, oscillatory or low WSS induces the secretion of pro-atherogenic substances, which carries a higher risk of plaque progression (1). As a result, atherosclerotic plaques are more frequently located at regions with low WSS, such as at the inner walls of curved arteries (2–4).
Coronary stenting also modifies shear stress. The local WSS decreases along the entire length of the stent after implantation (5). Moreover, stented regions exposed to lower WSS have been shown to exhibit higher grades of neointimal response compared with regions with physiological WSS; this has been shown to be applicable for both bare-metal stents (BMS) and paclitaxel-eluting stents (PES) at 6-month follow-up (6,7). Consequently, straightening of curved coronary arteries after implantation has been related to a higher neointimal response with BMS and PES at midterm follow-up (7–9). Conversely, sirolimus-eluting stents (SES) have been demonstrated to avoid the relationship between low WSS and a higher neointimal response at 6 months (7). As a result, some clinical studies using first-generation SES showed no relationship between angulated lesions and angiographic restenosis at 9 months (10,11). It is still unknown whether the progressive loss of angiographic minimal lumen diameter (MLD) experienced by the SES at long-term follow-up can modify the relationships among artery bend, curvature, and angulation with stent restenosis (12). At 2 years, SES and PES presented with similar angiographic lumen loss (12).
The most important device property that determines acute changes in coronary geometry is the conformability of the stent. Stent conformability is dependent on both material and design (13). The everolimus-eluting bioresorbable vascular scaffold (BVS) have shown better conformability in its ability to adapt to the coronary geometry immediately after implantation, compared with the Multi-link Vision and Xience V metallic platform stents (MPS) (Abbott Vascular, Santa Clara, California) (14). However, both the MPS and BVS devices have previously been demonstrated to decrease the artery curvature and angulation from pre- to post-implantation (14). Therefore, it is uncertain how these changes in artery geometry are maintained in both devices at midterm follow-up. This fact is especially important with the BVS, because bioresorption of the polymeric scaffolds might potentially allow for the restoration of the coronary artery to its original anatomical configuration seen before implantation. By design, the mechanical integrity of the BVS and the scaffold support to the artery wall eventually disappear a few months after the implantation (15), with complete resorption of the polymer approximately 2 years after implantation (16).
The aim of the present study is to compare the changes in coronary geometry from post-implantation to 6 to 12 months of follow-up between BVS and MPS. The clinical outcomes of both BVS and MPS are also explored.
Population and study design
The ABSORB Cohort B (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System [BVS EECSS] in the Treatment of Patients With de Novo Native Coronary Artery Lesions) trial is a single-arm trial that included 101 patients treated with a single 3.0 × 18 mm BVS. The global population was divided into 2 groups with different invasive angiographic controls at 6-month (n = 45) and 12-month (n = 56) follow-up. The study design and the clinical outcomes of the first cohort of patients (with 6-month follow-up invasive control) have been reported (17). The SPIRIT (A Clinical Evaluation of the XIENCE V Everolimus Eluting Coronary Stent System in the Treatment of Patients With de Novo Native Coronary Artery Lesions) I trial is a randomized trial that included 60 patients treated with a single Xience V (n = 28) or a Multi-link Vision (n = 32) 3.0 × 18 mm stent. The SPIRIT II trial randomized 300 patients to PES or to Xience V stent. A total of 223 patients were treated with different sizes of Xience V stent. All patients included in the SPIRIT I and II trials were scheduled for an angiographic control at 6-month follow-up.
The study design and clinical outcomes of the SPIRIT I and II trials have been reported (18,19). In brief, the inclusion criteria of the ABSORB and SPIRIT trials were similar: patients with stable or non–ST-segment elevation acute coronary syndrome and with a de novo lesion in a native coronary artery with a diameter stenosis (DS) between 50% and 99% were eligible. Patients with ostial lesions, heavily calcified arteries, or extreme angulated lesions (>90°) were excluded.
Acute changes in coronary geometry assessed before and after implantation of both BVS and MPS (Multi-link Vision or Xience V) have previously been investigated and reported by our group (14). In brief, 89 patients included in the ABSORB Cohort B trial treated with the BVS and 102 patients of the SPIRIT I and II trials treated with the Multi-link Vision or Xience V stents were included (14). This report presents a continuation of the previous study with the same population that underwent angiographic control at 6- or 12-month follow-up.
Treatment procedure and devices
All lesions were treated with routine interventional techniques that included mandatory pre-dilation with a balloon shorter and 0.5 mm smaller in diameter than the study device. Post-dilation with a balloon shorter than the implanted device was allowed at the discretion of the operator, as was bailout treatment.
The ABSORB Bioabsorbable Vascular Scaffold (Abbott Vascular) is a device consisting of a backbone of a fully resorbable polymer (poly-L-lactide), coated with a copolymer (poly-d,l-lactide) that contains and releases the antiproliferative drug (everolimus). Two platinum markers at each end outline the boundaries of the scaffold and remain embedded in the coronary wall after the scaffold resorbs. The Multi-link Vision and the Xience V stents (Abbott Vascular) share the same metallic platform composed of a cobalt-chromium alloy. The Xience V stent is coated with a biocompatible fluorinated copolymer that contains and releases the same amount of antiproliferative drug (100 μg/cm2 of everolimus) within a similar period.
Quantitative coronary angiography analysis
The operators were requested to select an angiographic view with minimal foreshortening of the lesion and limited overlap with other arteries. This angiographic view was used at baseline (before and after implantation) and at follow-up. The 2-dimensional angiograms were analyzed by an independent core laboratory (Cardialysis, Rotterdam, the Netherlands) with the CAAS II analysis system (Pie Medical BV, Maastricht, the Netherlands). In each patient, the treated region and the peri-treated regions (defined by 5 mm proximal and distal to the device edge) were analyzed. The following quantitative coronary angiography (QCA) parameters were measured: the interpolated-reference artery diameter, the MLD, and the percentage DS. Late luminal loss was derived from the difference between the MLD after implantation and at follow-up with matched angiographic views.
Curvature and angulation were measured before and after implantation and at follow-up with the same angiographic views (with a maximal difference of 10°). Both parameters were assessed within the treated region with clear landmarks to assess the treated region before implantation and with the radio-opaque markers after implantation and at follow-up. Both curvature and angulation were estimated with QCA (CAAS II version 1.2 Beta or CAAS 5.9 research version; Pie Medical Imaging) as previously reported (14). Briefly, “curvature” is defined as the infinitesimal rate of change in the tangent vector at each point of the center-line. This measurement has a reciprocal relationship to the radius of the perfect circle defined by the curve at each point. The curvature value is calculated as 1/radius of the circle in cm−1 (14). “Angulation” is defined as the angle in degrees that the tip of an intracoronary guidewire would need to reach the distal part of a coronary bend (14). Cyclical changes in coronary curvature and angulation were estimated as: curvature/angle at the end-diastole − curvature/angle at the end-systole. End-diastole curvature/angulation was assessed in the still angiographic view corresponding to the peak of the QRS complex of the electrocardiogram; and end-systole curvature/angulation was assessed in the still angiographic view corresponding with the peak of the T wave of the electrocardiogram. Relative differences, before and after implantation, were estimated at the end-diastole as: (absolute difference in curvature or angulation between pre- and post-implantation/curvature or angulation at pre-implantation) × 100.
The Kolmogorov-Smirnov test was used to evaluate the normality assumptions of all continuous variables. Because curvature, angulation, and cyclical changes of curvature and angulation did not have a normal distribution, all QCA geometry variables were expressed as median (interquartile range). The rest of the continuous variables were expressed as mean ± 1 SD. Categorical variables were presented as counts (%). Paired comparisons of continuous variables within groups between different time-points were estimated with the Wilcoxon test. Nonpaired comparisons between BVS and MPS were estimated with the Mann-Whitney U test when variables were non-normally distributed and with the Student t test when normally distributed. Comparisons of categorical variables were estimated with the chi-square test.
To assess the interobserver reproducibility of curvature and angle measurements, 2 observers analyzed 40 randomly selected cases. The interobserver reproducibility was assessed with the r2 Pearson correlation coefficient and the interclass correlation coefficient for absolute agreement (ICCa). An ICCa <0.4 indicated bad agreement, an ICCa between 0.4 and 0.75 indicated moderate agreement, and ICCa values >0.75 indicated excellent agreement (20).
All statistical tests were carried out with a 2-sided 5% level of significance. All measures were obtained with the SPSS software (version 15.0, SPSS, Inc., Chicago Illinois).
Population and baseline clinical characteristics
A total of 86 patients treated with BVS and 75 patients treated with MPS (58 Xience V, and 17 Multi-link Vision) were included in the present study. A flow chart of the patient selection is shown in Figure 1. Briefly, 30 patients were excluded because of: declined invasive angiographic follow-up, different angiographic views between baseline and follow-up, target lesion revascularization (TLR) before the scheduled invasive control, and damage to the data storage media. Angiographic follow-up of the BVS group was performed at 6 months in 37 patients and at 12 months in 49 patients. All patients treated with MPS were planned for invasive angiographic follow-up at 6 months.
The baseline clinical characteristics are shown in Table 1. Both groups were similar in age, sex, and cardiovascular risk factors except for smoking history (BVS 16.3% vs. MPS 37.3%; p < 0.01). Although there were no differences in the treated artery, the BVS group had a trend toward more patients with the culprit lesion located in the right coronary artery (33.7% vs. 20.9%, respectively). The left anterior descending was the most commonly treated artery with both BVS and MPS (45.4% vs. 50.7%, respectively).
Angiographic changes unrelated to coronary geometry
Angiographic findings unrelated to coronary geometry are shown in Table 2. Both BVS and MPS showed similar angiographic parameters before implantation. After implantation the BVS demonstrated a smaller MLD (2.05 mm vs. 2.14 mm, respectively; p < 0.01) and higher DS (15.4% vs. 12.7%, respectively; p < 0.01) compared with MPS. At follow-up, the DS, MLD, and late luminal loss were nonstatistically different between BVS and MPS.
Angiographic changes related to coronary geometry
Angiographic findings related to coronary geometry are shown in Table 3. Before implantation both groups presented with similar median values of curvature (BVS 0.297 cm−1 and MPS 0.365 cm−1; p = 0.99) and angulation (33.1° vs. 36.5°, respectively; p = 0.84). Cyclical changes in curvature (0.109 cm−1 vs. 0.091 cm−1, respectively; p = 0.80) and angulation (5.6° vs. 8.4°, respectively; p = 0.11) were also similar between groups.
From pre- to post-implantation, curvature and angulation significantly decreased in both groups. However, the BVS group experienced a smaller reduction in curvature (15.3% vs. 21.9%, respectively; p = 0.11) and angulation (17.4% vs. 31.8%, respectively; p = 0.02) compared with MPS. The BVS also presented with a smaller decrease in systo-diastolic (cyclical) changes in curvature (23.1% vs. 39.9%, respectively; p = 0.09) and angulation (29.6% vs. 51.0%, respectively; p = 0.06) compared with MPS.
From post-implantation to follow-up, the BVS showed an 8.4% increase in curvature (p < 0.01) and 11.3% increase in angulation (p < 0.01). Conversely, the MPS remained with a similar curvature (1.9% reduction, p = 0.54) but presented with a mild increase in angulation (3.8%, p = 0.01). The comparison of the absolute changes in curvature and angulation from post-implantation to follow-up between BVS and MPS was statistically significant for both parameters. The cyclical changes in coronary curvature and angulation observed at follow-up were similar to that observed after implantation in both groups, without any significant differences between devices.
From pre-implantation to follow-up, the BVS demonstrated a trend toward a reduction in artery curvature (3.4%; p = 0.05) and angulation (3.9%; p = 0.16). However, the MPS demonstrated a significant reduction in curvature of 26.1% (p < 0.01) and a reduction in angulation of 26.9% (p < 0.01); this was shown to be significantly larger than the BVS (p < 0.01 for curvature and angulation). Similarly, the BVS experienced fewer changes of systo-diastolic changes in curvature (19.7% reduction; p = 0.11) and angulation (0.3% increase; p = 0.51). However, the MPS showed an important decrease in cyclical changes of curvature (39.0%; p < 0.01) and angulation (49.9%; p < 0.01). The comparison between devices resulted in a lower reduction with the BVS compared with the MPS for cyclical changes in angulation (p < 0.01) but not for the cyclical changes in curvature (p = 0.27).
Geometric changes in coronary geometry in the subset of patients with larger pre-implantation curvature and angle
Because geometric changes are expected to be greater in curved arteries compared with straight arteries; the one-half of the overall population with larger median values of curvature (≥0.324 cm−1) and angulation (≥34.3°) before implantation were selected and are shown in Figure 2.
From pre- to post-implantation, the BVS demonstrated a smaller reduction in curvature (from 0.579 to 0.480 cm−1; 15.9%) compared with MPS (from 0.553 to 0.400 cm−1; 25.5%); this difference almost reached statistical significance when both scaffolds were compared (p = 0.09). The BVS also showed a trend toward a lower reduction in angulation (from 57.7° to 43.9°; 20.6%) compared with MPS (from 56.7° to 36.4°; 36.1%); without statistical significance (p = 0.14).
From post-implantation to follow-up, the BVS showed a 6.2% increase in artery curvature (from 0.480 to 0.547 cm−1) and a 7.8% increase in angulation (from 43.9° to 52.8°; 7.8%). The MPS demonstrated a 3.7% reduction in curvature (from 0.400 to 0.356 cm−1) and 3.2% increase in angulation (from 36.4° to 35.7°). As a result, the BVS had a statistically significant larger increase in curvature and angulation than MPS (p < 0.01 for both measurements).
From pre-implantation to follow-up, the BVS demonstrated a 0.019 cm−1 (3.4%) reduction in curvature and a 6.1° (10.4%) reduction in angulation. The MPS demonstrated a 0.211 cm−1 (39.1%) reduction in curvature and a 20.1° (32.6%) reduction in angulation. The absolute reduction in curvature and angulation were significantly lower with the BVS compared with the MPS (p < 0.01 for both curvature and angulation).
Geometric changes of the BVS group at 6- and 12-month follow-up
Figure 3 shows the individual data of the BVS patients divided according to the invasive follow-up (6 vs. 12 months). From post-implantation to follow-up, the cohort of patients who underwent 12-month follow-up tended to have larger changes in curvature (14.8% vs. 2.9%, respectively; p = 0.24) and angulation (11.4% vs. 6.2%, respectively; p = 0.36) compared with the cohort of patients who had 6-month follow-up.
Clinical outcomes related to coronary curvature/angulation
A total of 191 patients (89 BVS and 102 MPS: 77 Xience V and 25 Multi-link Vision) were investigated before implantation for geometric parameters. There were no deaths during the first year of follow-up. A total of 14 patients (7.3%) presented with TLR during the first 12 months after implantation: 4 patients (4.5%) treated with the BVS, 3 patients (3.9%) treated with the Xience V stent, and 7 patients (28.0%) treated with the Multi-link Vision stent. None of the patients with TLR were diabetic. All TLR events were ischemia-driven, except for 2 patients (1 BVS and 1 Multi-link Vision).
Figure 4 shows the box-plot values of curvature and angulation before implantation according to the treatment device. In the overall population, patients with TLR at 1 year showed larger median values of curvature (0.454 cm−1 vs. 0.307 cm−1, respectively; p = 0.72) and angulation (41.9° vs. 31.4°, respectively; p = 0.23) compared with patients without TLR, although these differences did not reach statistical significance.
Reproducibility of curvature and angle measurements
Interobserver reproducibility for curvature assessment had an r2 Pearson correlation coefficient of 0.84 and ICCa of 0.92 (excellent agreement). The mean ± SD difference between observers was 0.022 ± 0.175 cm−1. Interobserver reproducibility for angulation assessment was 0.86 for the r2 Pearson correlation coefficient and 0.91 for the ICCa (excellent agreement). The mean ± SD difference between observers was 5.3° ± 11.2°.
The major findings of the present study are: 1) both BVS and MPS decreased the coronary curvature, angulation, and systo-diastolic changes from pre- to post-implantation; 2) from post-implantation to follow-up, the BVS significantly increased the artery curvature and angulation except for the systo-diastolic changes in curvature and angulation, and the MPS showed a slight increase in angulation but retained the artery curvature and the systo-diastolic changes in curvature and angulation as measured after implantation; 3) at follow-up, the BVS presented with a minor reduction in coronary curvature with respect to that seen before implantation, although the coronary angulation and the cyclical changes in curvature and angulation were similar to that seen before implantation; and 4) from pre-implantation to follow-up, the MPS presented with an important reduction in all geometric parameters. These results were larger and more evident when the one-half of the population with higher values of curvature and angulation was investigated.
To the best of our knowledge, the present study is the first to report an increase in geometric parameters from post-implantation to follow-up in scaffolded segments. At 6- or 12-month follow-up, the anatomical configuration of the arteries treated with the ABSORB BVS allowed restoration of coronary geometry to values close to those measured before implantation. However, these differences were slightly different according to the follow-up. Patients with angiographic control at 12 months tended to show larger changes in geometric parameters compared with patients with angiographic control at 6 months. Figure 5 shows the changes in coronary geometry in 2 patients treated with the BVS and imaged at different follow-up periods (6 and 12 month). The most plausible explanation for the coronary geometric changes observed in the present study is the gradual reduction in artery support and disappearance of the mechanical integrity of the scaffold in most of the patients at 6- to 12-month follow-up but especially in those patients who underwent angiographic control at 12 months. The first-generation BVS (1.0) showed an accelerated loss of the artery support during the first 6 months that resulted in an important shrinkage of the scaffold (21). The new generation of BVS (ABSORB) was redesigned to slow down the loss of artery support, compared with its previous generation, through modification of the manufacturing processes of the polymer and platform design (17). According to the manufacturer, the artery wall support provided by the ABSORB BVS is designed to gradually decrease during this period of restoration (3 to 12 months). By the end of the first year, the vast majority of amorphous polymer that links the crystalline lamella is hydrolyzed (15). Therefore, the scaffold has gradually lost continuity of structure, allowing restoration of the original anatomical configuration.
The potential clinical implications related to the restoration of the coronary geometry at follow-up are uncertain. It is noteworthy that, before the scaffold implantation, the physiological geometry of the treated segment developed an atherosclerotic lesion. The first bioresorbable scaffolds implanted in human coronary arteries (Igaki-Tamai, Igaki Medical Planning Company, Kyoto, Japan) have fulfilled 10-year clinical and intravascular ultrasound follow-up. The intravascular ultrasound imaging in patients that required TLR at long-term follow-up showed the presence of neoatherosclerotic plaques within the scaffolded segment (22). Therefore, it seems plausible that the restoration of the coronary anatomical configuration similar to that seen before implantation might also potentially restore the WSS conditions that triggered the formation of atherosclerotic plaques, if drastic preventive measures are not taken.
Conversely, Figure 4 shows a trend toward higher values of curvature and angulation before implantation in patients with TLR at 12 months, compared with those without revascularization. These differences mildly differed, depending on the implanted stent/scaffold. With BVS, differences in curvature and angulation before implantation in patients without TLR (median values: 0.292 cm−1 and 32.6°, respectively) and with TLR at 12 months (0.280 cm−1 and 33.1°, respectively) were minimal (p = 0.74 and p = 0.99, respectively). With MPS, curvature and angulation tended to be slightly smaller in patients without TLR (0.318 cm−1 and 31.4°, respectively), compared with patients with TLR at 12 months (0.519 cm−1 and 46.4°, respectively); p = 0.48 and p = 0.14, respectively. However, the present study was not sufficiently powered to relate coronary geometric parameters with clinical outcomes, and these results should be interpreted carefully.
Previous reports using BMS found higher risk of restenosis in angulated and curved arteries. A pre-treatment angulation ≥33.5° was found as an independent predictor of restenosis at 10 months of follow-up (8). However, with the use of SES, to date no study has been able to relate the artery curvature/angulation before implantation with a greater neointimal response or higher risk of restenosis (7,10,23). However, most of these studies are limited to clinical outcomes at midterm follow-up. It is uncertain whether the progressive late lumen loss experienced by SES at long-term follow-up can modify the relationship between artery bend, curvature, and angulation and stent restenosis at longer-term follow-up. The first-generation SES has shown a progressive reduction of MLD from 6 to 18 months of 0.28 mm, whereas the delayed late lumen loss was smaller with the first-generation PES in the same period (0.10 mm; p < 0.01) (12). The Xience everolimus-eluting stent has also been associated with a progressive reduction in the MLD from 6 to 24 months (delayed late lumen loss of 0.16 mm) and therefore can also be influenced by the effect of WSS at long-term follow-up (24).
The first limitation of the present study is the use of 2-dimensional images to assess the geometric parameters of coronary arteries. Coronary arteries have a 3-dimensional geometric shape that is in continuous movement (4-dimensional), despite the use of the least foreshortened view. For these reasons, the 2-dimensional analysis of coronary geometry is clearly biased by foreshortening of the angiographic views. However, a reliable 3-dimensional reconstruction of coronary arteries, based on angiographic images, requires a biplane system or rotational angiography (25,26). Almost all images of patients included in the ABSORB and SPIRIT trials were acquired with monoplane angiograms in such way that the 3-dimensional reconstruction would not have been reliable. Second, the non-normal distribution of curvature and angulation values, with a relatively high number of extreme values, caused a moderate variability for repeated measures between different observers when extreme values of curvature and angulation were assessed. The exclusion of extreme curved and angulated lesions (curvature >0.900 cm−1 and angulation >90°) substantially improved the variability between observers to 0.016 ± 0.086 cm−1 for curvature and 4.3 ± 7.2° for angulation. The results of the present study were also reproducible (data not shown), taking into account the interobserver variability for repeated measurements (2× SD), with and without extreme values. The third limitation is the small number of patients included in our study. The possible relationship between coronary geometry and clinical outcomes reported in the present study is clearly underpowered and needs to be interpreted with caution. Finally, the fourth limitation of the study is the difference in the time of follow-up of the ABSORB trial patients. It was decided, as per protocol, to split the population into 2 groups to assess the bioresorption process with multiple intravascular imaging techniques in different time-points. Although a possible restoration of the coronary artery to its pre-implantation anatomical configuration in patients treated with metallic stents at 12-month follow-up seems improbable, we do not have angiographic control at 12 months for MPS SPIRIT patients.
At midterm follow-up, the BVS tended to allow restoration of the coronary geometry and systo-diastolic movements of the coronary arteries similar to that seen before implantation. Coronary geometry and systo-diastolic movements of coronary arteries treated with MPS remained similar to that seen after implantation. Potential clinical benefits of restoring the pre-implantation coronary anatomy will require longer-term clinical follow-up in a larger patient group.
The authors thank Pie Medical for reviewing the manuscript. The authors also thank the Biomedical Research Institution of Bellvitge (IDIBELL) for the grant awarded to Dr. Gomez-Lara.
The ABSORB Cohort B and the SPIRIT I and II trials have been supported by Abbott Vascular. Dr. Windecker has received research grants from Abbott, Cordis, Medtronic, Biosensors, and Boston Scientific. Dr. Dudek has received research grants or served as a consultant/advisory board member for Abbott, Adamed, AstraZeneca, Biotronik, Balton, Bayer, BBraun, BioMatrix, Boston Scientific, Boehringer Ingelheim, Bristol-Myers Squibb, Cordis, Cook, Eli Lilly, EuroCor, GlaxoSmithKline, Invatec, Medtronic, The Medicines Company, Merck Sharp & Dohme, Nycomed, Orbus-Neich, Pfizer, Possis, Promed, Sanofi-Aventis, Siemens, Solvay, Terumo, and Tyco. Dr. Smits has received speaker and travel fees from Abbott Vascular. Dr. Chevalier is a consultant for Abbott Vascular. Cécile Dorange, Susan Veldhof, and Dr. Rapoza are employees of Abbott Vascular. Dr. Ormiston is on the advisory boards for Abbott and Boston Scientific; and has received minor honoraria from Abbott and Boston Scientific. All other authors have reported that they have no relationships to disclose. Eric Bates, MD, served as Guest Editor for this paper.
- Abbreviations and Acronyms
- bare-metal stent(s)
- bioresorbable vascular scaffolds
- diameter stenosis
- interclass correlation coefficient for absolute agreement
- minimal lumen diameter
- metallic platform stent
- paclitaxel-eluting stent(s)
- quantitative coronary angiography
- sirolimus-eluting stent(s)
- target lesion revascularization
- wall shear stress
- Received January 25, 2011.
- Revision received March 29, 2011.
- Accepted April 11, 2011.
- American College of Cardiology Foundation
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