Author + information
- Koen Nieman, MD, PhD†,‡∗ (, )
- Patrick W. Serruys, MD, PhD†,
- Yoshinobu Onuma, MD†,
- Robert-Jan van Geuns, MD, PhD†,
- Hector M. Garcia-Garcia, MD, PhD†,
- Bernard de Bruyne, MD, PhD§,
- Leif Thuesen, MD‖,
- Pieter C. Smits, MD, PhD¶,
- Jacques J. Koolen, MD, PhD#,
- Dougal McClean, MD∗∗,
- Bernard Chevalier, MD††,
- Ian Meredith, MD‡‡ and
- John Ormiston, MD, PhD§§
- †Department of Cardiology, Erasmus Medical Center, Rotterdam, the Netherlands
- ‡Department of Radiology, Erasmus Medical Center, Rotterdam, the Netherlands
- §Department of Cardiology, Cardiovascular Center, Aalst, Belgium
- ‖Department of Cardiology, Skejby Sygehus, Aarhus, Denmark
- ¶Department of Cardiology, Maasstad Hospital, Rotterdam, the Netherlands
- #Department of Cardiology, Catharina Ziekenhuis, Eindhoven, the Netherlands
- ∗∗Department of Cardiology, Christchurch Hospital, Christchurch, New Zealand
- ††Department of Cardiology, Institut Jacques Cartier, Massy, France
- ‡‡Department of Cardiology, Monash Cardiovascular Research Center, Melbourne, Australia
- §§Department of Cardiology, Auckland City Hospital, Auckland, New Zealand
- ↵∗Erasmus Medical Center, Department of Cardiology, Room Bd-116, ‘s-Gravendijkwal 230, 3015 CE, Rotterdam, the Netherlands
To the Editor:
Although metal stents revolutionized the treatment of coronary artery disease, concerns exist about their indefinite presence and the risk of late stent thrombosis. This may be resolved by biodegradable devices that provide initial support but dissolve over time to restore native vessel integrity. Because the first-generation Absorb (Abbott Vascular, Santa Clara, California) everolimus-eluting bioresorbable vascular scaffold (BVS) demonstrated late lumen loss thought to be caused by rapid changes in strut integrity (1), the second generation was designed for improved mechanical endurance and prolonged radial force. The metal-free struts allow unrestricted coronary computed tomography angiography (CCTA). CCTA-based fractional flow reserve (FFRCT) for functional coronary artery disease assessment was recently introduced (2,3). In this study, we evaluate the midterm clinical, angiographic, and functional outcome of the second-generation Absorb BVS.
The ABSORB (A Clinical Evaluation of the Bioabsorbable Everolimus Eluting Coronary Stent System in the Treatment of Patients With de Novo Native Coronary Artery Lesions) trial (NCT00856856) is a nonrandomized multicenter, single-arm, efficacy-safety study. At 12 centers, 101 patients (62.3 ± 8.9 years of age, 73 male) with 102 de novo lesions were treated with a second-generation Absorb BVS (3). The balloon-expandable Absorb BVS (diameter 3.0 mm, area 7.1 mm2) has a polylactide backbone containing the antiproliferative drug everolimus. Elective procedures by standard percutaneous coronary intervention techniques included mandatory pre-dilation. The clinical composite endpoint at 18 months was cardiac death, myocardial infarction, or ischemia-driven target lesion revascularization, as previously described (4).
Nine centers (79 patients) performed CCTA in 71 patients (90%) with the use of 64-slice computed tomography technology or beyond by standard techniques. The median radiation dose was 6.8 mSv (1.3 to 22.3 mSv). Vessel cross-sections were reconstructed at approximately 1-mm longitudinal increments, extending 5 mm beyond the device, using the remaining platinum scaffold indicators as landmarks (Circulation, Siemens AG, Forchheim, Germany). After semiautomatic vessel lumen delineation, mean, minimal lumen area (MLA), and maximum lumen areas were determined. The reference lumen area was calculated as the average between the mean vessel area proximal and distal to the scaffolded segments. Area stenosis, defined as the difference between the MLA and the reference as a percentage of the reference, ≥75% was considered significant (Fig. 1).
The FFRCT analysis was performed by HeartFlow, Inc. (Redwood City, California). The methodology of FFRCT has been described by Taylor et al. (3). On the basis of physiological modeling, with input of clinical and CCTA data, coronary blood flow and pressure during hyperemia can be simulated. An FFRCT <0.80, defined as the ratio between coronary and aortic computed mean pressure, was considered significant. The FFRCT gradient was calculated as the difference in FFRCT proximal and distal to the scaffold site.
Continuous variables are presented as mean ± SD or median (range). The Pearson coefficient was calculated to assess the correlation among the MLA, area stenosis, and fractional flow reserve gradient (SPSS version 17.0, SPSS Inc., Chicago, Illinois). No formal power calculation was performed.
At 18 months, there were no cardiac deaths and 3 non–Q-wave myocardial infarctions: 2 during the index procedure, 1 during an intercurrent invasive investigation, and 5 ischemia-driven target lesion revascularizations. The hierarchical major adverse clinical cardiac event rate was 7.9% (n = 8).
Four CCTA scans (6%) were entirely noninterpretable, and 6 scans (8%) were only qualitatively evaluable. One of these showed ≥50% stenosis, which was managed conservatively in the absence of symptoms. Quantitatively (n = 61), the average mean in-scaffold lumen area was 5.1 ± 1.4 mm2 (2.6 to 8.2 mm2), the proximal and distal reference areas were 5.3 ± 2.0 mm2 and 4.3 ± 1.5 mm2, respectively, the MLA was 3.5 ± 1.0 mm2 (1.6 to 5.6 mm2), and the maximum lumen area was 7.0 ± 2.1 mm2 (3.1 to 13.3 mm2). The average area stenosis was 22.7 ± 22.4% (−64.2% to +72.0%). The MLA was <25% of nominal in 1 case of a small posterolateral branch (MLA 1.6 mm2, reference 2.1 mm2).
FFRCT could be performed in 38 patients (57%) and measured 0.92 ± 0.06 (0.77 to 0.99) proximal and 0.89 ± 0.06 (0.74 to 0.97) distal to the scaffolded segment, with an average gradient of −0.03 ± 0.04 (+0.01 to −0.23). There was no significant correlation between area stenosis and MLA or FFRCT gradient. The largest FFRCT gradient (−0.23) was associated with only 9.4% area stenosis, an MLA of 3.2 mm2, and low FFRCT values in all distal branches, suggesting systematic underestimation. The FFRCT gradient ranged between −0.02 and −0.09 in patients with an area stenosis ≥50%.
For decades, new percutaneous coronary therapies have required invasive angiography to assess late lumen loss. Considering the good diagnostic accuracy of CCTA in the absence of metal stents (5) and the advantages in safety, patient convenience, and cost, CCTA offers a noninvasive alternative to catheterization for both clinical care and research. In this population, significant re-stenosis after Absorb BVS treatment was detected by CCTA in only 1 patient.
Study limitations are the nonrandomized design, cardiac CT unavailability at 3 sites, and frequent noninterpretable FFRCT analyses. The observation of absent hemodynamic significance by FFRCT in patients with mild stenosis should be interpreted as explorative while the technique is further investigated.
The clinical event rate was acceptable (7.9%), and angiographic patency by CCTA was good 18 months after implantation of the second-generation Absorb BVS.
Please note: This work was supported by Abbott Vascular, Santa Clara, California. Dr. Nieman has received research support by Siemens Medical Solutions, GE Health Care, and Bayer Schering. Dr. de Bruyne is a consultant to St. Jude Medical. Dr. Smits has received speaking fees from Abbott Vascular and Terumo. Dr. Chevalier is a consultant to Abbott Vascular. Dr. Meredith serves on the Boston Scientific and Medtronic strategic advisory boards and receives an honorarium payment for this role. Dr. Ormiston is on advisory boards for Abbott Vascular and Boston Scientific. All other authors have reported they have no relationships relevant to the contents of this paper to disclose.
- American College of Cardiology Foundation
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