From October 2012 to December 2015, all consecutive patients treated at the University of Giessen, Medizinische Klinik I, Department of Cardiology, Germany, within the scope of an all-comers registry and with a minimum total scaffold length of 28mm per vessel, irrespective of the number of BRS, were included in the study. To evaluate the potential impact of overlapping BRS on outcomes, the population with successful BRS implantation was divided post hoc into 2 subgroups to compare patients with overlapping BRS with those without overlap. We excluded patients treated with overlapping BRS at one site and not overlapping BRS at another site from this subgroup analysis.

The general inclusion criteria of this all-comers registry were any evidence of ischemia in a 12-lead electrocardiogram, elevated cardiac biomarkers or symptoms of angina pectoris, and angiographic eligibility for BRS implantation. Further details haven been published previously.10

The circumferential and cross-linked struts of the Absorb BRS are made of poly-L-lactic acid with a thickness of 150μm. The Absorb BRS elutes a 1:1 mixture of poly-D, L-lactic acid and the antiproliferative drug everolimus. To ensure visualization, radiopaque markers are located at the tip of each end. In a porcine model, complete dissolution of the scaffold was observed after 2 years.7

The implantation of the BRS was performed according to standard clinical practice. Prior to the procedure, 70 U/kg body weight of unfractionated heparin was administered. For predilatation a noncompliant or, if required, a scoring balloon was used. Postdilatation was strongly recommended.

To guarantee a minimal overlap, the BRS were implanted in a marker-to-marker fashion: once the first BRS was implanted, the second BRS was positioned with its balloon marker directly over the marker of the first BRS. Thus, the radiopaque markers of both BRS were located directly next to each other. This technique leads to a minimal overlap zone of approximately 1mm.

Intravascular imaging included optical coherence tomography (ILUMIEN OPTIS, Dragonfly, St. Jude Medical, Inc.; St. Paul, Minnesota, United States) or intravascular ultrasound (Eagle Eye Gold, Volcano Corp.; San Diego, California, United States) and was used in certain cases for measurement of the lumen diameter and vessel characteristics according to the discretion of the implanting physician (Figure of the supplementary material).

Procedural success was defined as successful deployment of the BRS at the target lesion and an estimated residual stenosis equal to or less than 30% as visualized by angiography. The postprocedural antiplatelet regimen was administered according to existing guidelines.5

Baseline evaluation contained documentation of the patients’ medical history, physical examination, 12-lead electrocardiogram, and blood laboratory examination. Follow-up was conducted either by office visits or by telephone interviews after 30 days, 6 months, 12 months, and then yearly.

All examinations were performed according to the Declaration of Helsinki. The patients received and signed a written consent form. This study was approved by the Ethics Board of the Justus Liebig University of Giessen, Giessen, Germany (AZ: 246/12).

Major adverse cardiac events (MACE) consisted of cardiac death, myocardial infarction, or clinically driven percutaneous or surgical target lesion revascularization (TLR). The device-oriented composite endpoint of target lesion failure (TLF) consisted of cardiac death, target-vessel myocardial infarction, or TLR. Target vessel failure (TVF) included cardiac death, target vessel myocardial infarction, or clinically driven percutaneous or surgical target vessel revascularization. Scaffold thrombosis was defined according to Academic Research Consortium criteria.11 These endpoints were assessed after 1 year.

Continuous variables are presented as mean±standard deviation or as median [interquartile range]. Categorical variables are presented as counts and percentages. To compare the 2 groups the Mann-Whitney-Wilcoxon U test was used for continuous variables, and the Fisher exact test or the chi-square test was applied for categorical variables. All tests were 2-tailed and a P-value<.05 was considered statistically significant. The Kaplan-Meier method was used to calculate event rates and the log rank test was used for comparisons.

A total of 250 patients with a minimum total scaffold length of 28mm per vessel were found to be eligible for this investigation. Baseline characteristics are presented in Table 1. Catheterization was indicated due to an acute coronary syndrome in 61.6% (154 of 250), stable coronary artery disease in 36.4% (91 of 250), and other reasons in 2.0% (5 of 250). Radial access was used in 62.0% (155 of 250) and femoral access in 38.0% (95 of 250). Most lesions were localized at the left anterior descending coronary artery (44.3%), and 30.8% of the lesions were categorized as A/B1 and 69.2% as B2/C according to the American Heart Association/American College of Cardiology classification. An average of 1.8±0.9 BRS were implanted per lesion: 1 BRS was required in 44.0% (120 of 273) of the lesions, 2 BRS were required in 37.7 (103 of 273), and more than 3 BRS were implanted in 18.3% (50 of 273). In 6 lesions, BRS implantation was unsuccessful because it was not possible to cross the lesion with the BRS; thus, the lesion-based procedural success was 97.8% (267 of 273). Thrombus aspiration was performed in 43 ST-segment elevation myocardial infarction cases. In 18 cases (7.2%) an additional scoring balloon was used for predilatation; rotational atherectomy was not used. Intravascular imaging (optical coherence tomography or intravascular ultrasound) was used to guide BRS implantation in 40.4% of all patients. Further procedural details can be found in Table 2.

The median length of follow-up was 362 [169.3-708.8] days; 62.1% of the patients (149 of 240) completed at least the 12 months’ follow-up and 2.4% (6 of 250) were lost to follow-up. An overview of clinical outcomes is presented in Table 3. Event rates after 1 year were 8.5% for MACE, 6.6 for TLF, 4.0% for TLR, 2.3% for scaffold thrombosis, and 1.5% for cardiac deaths (Figure 1). The 5 cases of scaffold thrombosis occurred 24hours and 4, 17, 38 and 77 days after BRS implantation, with 2 of these patients having discontinued their antiplatelet therapy. All incidences of scaffold thrombosis were classified as definite according to Academic Research Consortium criteria.

Figure 1.

Clinical outcomes at 12 months among patients undergoing long-segment stenting with BRS. A: MACE, comprising cardiac death, myocardial infarction or TLR. B: TLF, comprising cardiac death, target-vessel myocardial infarction or TLR. C: TLR. D: ST. BRS, bioresorbable scaffold; MACE, major adverse cardiac events; ST, scaffold thrombosis; TLF, target lesion failure; TLR, target lesion revascularization.

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Of all patients in the cohort, 239 met the criteria for subgroup analysis. Of these, 125 were treated with overlapping BRS and 114 were treated without overlapping BRS (Table 4). No differences were found between groups in baseline characteristics or clinical presentation. Femoral access was used similarly in both groups (40.8% vs 34.2%; P=.2937). General procedural parameters including procedure time, fluoroscopy time and contrast use were higher in the overlap group, but pre- and postdilatation were applied in a similar proportion (Table 4).

No differences were detected in the 12-month outcome during follow-up (Figure 2). When we compared patients in the total cohort with and without MACE, overlapping implantation of BRS was performed in the same proportion (47.1% [8 of 17] vs 54.9% [128 of 233]; P=.5290). In a Cox-regression analysis adjusted for age, sex and clinical presentation, overlap was not a predictor of MACE (P=.901; hazard ratio=1.056; 95% confidence interval, 0.446-2.499). Comparison of the outcome of patients with at least 1 overlapping BRS of 2.5mm in diameter (n=72) with those having overlapping BRS only larger than 2.5mm (n=53) revealed that the rates of MACE, TVF, TLR, and cardiac death were similar (Table 5).

Figure 2.

Comparison of the 12-month outcomes of patients with and without overlapping BRS. A: MACE, comprising cardiac death, myocardial infarction or TLR. B: TLF, comprising cardiac death, target-vessel myocardial infarction or TLR. C: TLR. D: ST. BRS, bioresorbable scaffold; MACE, major adverse cardiac events; ST, scaffold thrombosis; TLF, target lesion failure; TLR, target lesion revascularization.

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These real-world data were gathered in a nonrandomized fashion and there were no routinely performed angiographic follow-up examinations. Although the follow-up completion rate was high, some patients were lost to follow-up and the possibility that these patients experienced adverse events cannot be definitely ruled out. Post hoc subgroup analysis was performed without matching. Baseline characteristics, clinical presentation, and lesion classification, however, did not vary statistically significantly, and differences in procedural characteristics were expected. Due to the small number of patients, all results should to be interpreted with caution, especially regarding the stent thrombosis rate in the subgroup analysis of patients with overlaps including a 2.5mm BRS or larger BRS. However, a post hoc power calculation showed a power of 78.8% to detect differences in MACE. The number of patients is relatively low, and thus the statistical significance might be under- or overpowered.