The possibility of strut fractures after bioresorbable vascular scaffold (BVS) treatment is a new problem associated with the use of this novel technology. There is little in vivo information regarding the effects of lateral dilation on BVS. The present study aimed to evaluate the effects of lateral balloon dilation after bioresorbable vascular scaffold implantation in the treatment of bifurcation lesions. From January 2012 to February 2015, 49 patients with bifurcation lesions who had been treated with BVS required balloon dilation of the side branch (SB). Optical coherence tomographic studies were performed in each of these patients. In 3 patients (6%), the optical coherence tomographic results met the criteria for rupture. Prolonged inflation using a noncompliant balloon with a diameter within the expansion limits of the device resolved the complication in all patients. The clinical course was favorable in all patients, and there were no inhospital deaths or myocardial infarctions. At 14 ± 8 months of follow-up, 2 patients with integrity of the BVS presented target lesion revascularization (4%). Another patient (2%) suffered a probable stent thrombosis 11 months after the procedure (myocardial infarction and death at home). The patients with the BVS rupture at the index procedure had a favorable clinical outcome, and the 6-month computed tomographic scan revealed maintenance of the initial good results. In conclusion, minor BVS rupture after 2.5-mm lateral balloon dilation may occur but is infrequent (6%). Prolonged balloon inflation of the main vessel may partially restore the geometry of the BVS.
Fully bioresorbable vascular scaffolds (BVSs) have been demonstrated to be effective for the treatment of nonbifurcated coronary lesions. However, the possibility of strut fractures is a new problem with the use of this novel technology. The in vivo rupture of a BVS is a rare complication if the recommendations of the manufacturers are followed. For the treatment of bifurcation lesions, lateral dilation of the side branch (SB) ostium through the BVS structure may be necessary with the consequent risk of strut fractures. This problem has been studied in vitro, but no in vivo studies have been conducted to assess the effects of SB dilation across the BVS platform. The purpose of this study was to evaluate the effects of lateral balloon dilation after main vessel (MV) BVS implantation in patients with bifurcation lesions.
Methods
From January 2012 to February 2015, 564 patients with bifurcation lesions were treated by metallic stents and simple approach at our center, 265 (47%) of them needed SB postdilation. During this same period, another 124 patients with bifurcation lesions were treated with provisional BVS implantation and 49 (39%) of them needed SB postdilation and constitute our study series. The patients fulfilled the following inclusion criteria: (1) lesion located in a major bifurcation point; (2) MV ≥2.5 mm and ≤4 mm in diameter; (3) SB ≥2.0 mm and ≤3 mm in diameter; (4) significant stenosis at the SB ostium by visual inspection after MV BVS implantation; and (5) stenosis length <10 mm at the SB. The following exclusion criteria were used: (1) patients with contraindications to 1-year antiplatelet therapy; (2) cardiogenic shock; and (3) co-existing severe co-morbidities. In all the patients, a simple approach was used. After BVS implantation, the Thrombolysis In Myocardial Infarction (TIMI) flow and ostium stenosis at the SB were evaluated. In patients with a TIMI flow <III or severe SB stenosis, the SB was rewired, and balloon dilatation of the ostium was performed across the BVS. According to these criteria, lateral BVS dilation was required in 49 patients. This group of patients constituted our study group. The SB balloon diameter was selected on the basis of the SB diameter or a slightly less value. Postdilation of the BVS was performed when optical coherence tomography (OCT) demonstrated underexpansion, nonapposition BVS deformations or disruptures. All the patients were pretreated with dual-antiplatelet medication. The baseline bifurcation anatomy was assessed according to the Medina classification.
In the hemodynamics laboratory, the patients received a bolus of 100 IU/kg of intravenous unfractionated heparin. After the procedure, all the patients received 100 mg of aspirin daily indefinitely and a maintenance dose of clopidogrel (75 mg/day), prasugrel (10 mg/day), or ticagrelor (90 mg twice daily) for at least 12 months. Serial determinations of the troponin I and creatine kinase levels were performed before and after the procedure. Periprocedural MI was defined according to the new definition of clinically relevant MI after coronary revascularization, and scaffold thrombosis was defined according to the Academic Research Consortium criteria.
To assess BVS restenosis, a 6-month coronary computed tomography (CT) scan was recommended for every patient. Further cardiac catheterization was indicated in the presence of symptoms.
The OCT study was performed in all the patients after SB balloon dilation across the BVS. A Fourier-Domain OCT system (C7-XR; St. Jude Medical, St. Paul, Minnesota) was used to acquire the images. The diagnosis of BVS rupture was based on the following criteria: (1) struts protruding into the center of the lumen, (2) overlapped struts, and (3) struts not orientated perpendicular to the light source. If BVS balloon postdilation was required, an additional, final OCT study was obtained. Discrete variables are presented as counts and percentages, whereas continuous data are presented as the mean ± standard deviation.
Results
The baseline clinical and angiographic data are summarized in Table 1 . The bifurcation site was most frequently located at the left anterior descending artery/diagonal branch, and the most frequent Medina type was {1,1,1}. Table 2 provides a summary of the quantitative coronary analysis and procedural characteristics. Most of the SB were dilated with a 2.5-mm balloon; a maximal balloon diameter of 2.75 mm was used in 4 patients.
| Variables | |
| Age (years) | 54 ± 8 |
| Men | 48 (98%) |
| Hypertension | 28 (57%) |
| Diabetes | 8 (17%) |
| Hyperlipidemia | 22 (45%) |
| Current smoking | 27 (55%) |
| Acute coronary syndrome | 44 (90%) |
| Left ventricular ejection fraction (%) | 59 ± 10 |
| Angiographic data | |
| Location of the lesion (%) | |
| Distal Left Main | 2 (4%) |
| LAD-Diagonal branch | 33 (67.5%) |
| LC-Obtuse marginal | 11 (22.5%) |
| Right-Posterior descending artery | 3 (6%) |
| Type of lesion (%) | |
| {1,1,1 } | 23 (47%) |
| {1,1,0 } | 15 (31%) |
| {1,0,1 } | 3 (6%) |
| {0,1,1 } | 2 (4%) |
| {1,0,0 } | 2 (4%) |
| {0,1,0 } | 4 (8%) |
| Quantitative coronary analysis | Main vessel | Side branch |
|---|---|---|
| Lesion length (mm) | 19±12 | 8±4 |
| Reference diameter (mm) | 3.1±0.5 | 2.3±0.4 |
| Minimal lumen diameter pre (mm) | 0.7±0.6 | 1.4±0.8 |
| Minimal lumen diameter post (mm) | 2.8±0.4 | 2.1±0.5 |
| Percentage of stenosis pre (%) | 79±17 | 42±34 |
| Percentage of stenosis post (%) | 12±11 | 14±12 |
| Procedural data | |
|---|---|
| OCT guidance | 49 (100%) |
| BVS per lesion | 1.15±0.41 |
| BVS diameter (mm) | |
| 2.5 | 5 (10%) |
| 3.0 | 20 (41%) |
| 3.5 | 24 (49%) |
| BVS length (mm) | 23±12 |
| BVS inflation pressure (atmospheres) | 13 ± 2 |
| SB balloon diameter (mm) | 2.4 ± 0.25 mm |
| 1.50 | 1 (2%) |
| 2.0 | 9 (18.4%) |
| 2.25 | 3 (6.1%) |
| 2.50 | 32 (65.3%) |
| 2.75 | 4 (8.2%) |
| SB balloon pressure (atmospheres) | 10±2 |
| Correction of BVS distortion after SB dilation | |
| No correction | 31 (63%) |
| Single balloon post-dilation | 12 (25%) |
| Sequential balloon post-dilation | 5 (10%) |
| Undersized kissing | 1 (2%) |
The OCT studies after SB dilation across the BVS revealed mild deformations in 31 patients (63%). In the remaining 18 patients with BVS distortion induced by lateral dilation, different strategies were used to correct this deformation ( Table 2 ). Single MV balloon postdilation was the most commonly used technique to restore the BVS geometry. This strategy was also used in the 3 patients who fulfilled some of the criteria for BVS rupture ( Figures 1 and 2 and Table 3 ). The OCT criteria for BVS rupture in these patients are listed in Table 3 . Of these 3 patients, prolonged balloon inflation at MV was performed at nominal values in 2 patients and at a value that was 0.5 mm greater in the third patient. After the second OCT study, a significant improvement in BVS geometry was observed ( Figures 1 and 2 ). The struts protruding into the center of the lumen and the maloriented struts clearly disappeared in all 3 patients ( Table 3 ). In contrast, the overlapped struts remained unchanged despite MV balloon postdilation.
