Methods

The design of the ABSORB-CTO pilot study has been published previously. In our CTO program, before the procedure MSCT, cardiac magnetic resonance imaging, quality of life, and 6-minute walk test are recommended for all patients. From February 2013 until March 2014, 33 patients with 35 true CTO coronary lesions (EuroCTO definition), with vessel reference diameters between 2.5 and 3.5 mm, were enrolled. Major exclusion criteria were lesions located in the left main, true bifurcation lesions with a side branch ≥2.5 mm in diameter by visual assessment, the presence of any contraindication to implantation of a drug-eluting stent and reference vessel diameters. Angiographic target lesion calcification was not a predefined exclusion criteria but was left to operator’s discretion. From 49 clinically eligible patients with CTO, 14 patients (28.5%) were excluded because of the predefined angiographic criteria (n = 11: calcification and tortuosity lesions [5], true bifurcated lesions with a side branch reference diameter ≥2.5 mm [4], lesions with reference vessel diameter <2.5 mm [n = 1], or ≥4 mm [n = 1]) or because of procedural complications needing bailout stent implantation (n = 3: coronary perforation treated with stent graft, aorto-ostial dissection treated with a 4-mm DES, and distal coronary dissection after BVS implantation treated with 2.25-mm DES).

The second generation of Absorb-BVS comprises a poly-L-lactide backbone coated with a thin layer of a 1:1 mixture of poly-D, L-lactide polymer that contains and controls the release of the antiproliferative drug everolimus. Both poly-L-lactide (backbone) and poly-D, L-lactide (coating) are fully bioresorbable and degrade to lactic acid over 3 years.

Two experienced CTO operators performed all procedures ( Figure 1 ). After crossing the CTO with the guidewire, balloon dilation was performed first with small balloon sizes (1.5 or 2.0 mm). All patients underwent intravascular ultrasound (IVUS) before device implantation with 2 objectives: (a) to analyze the morphologic and anatomical characteristics of the lesion (fibrocalcific or calcified plaques not apparent in previous angiography, areas of inadequate expansion, etc.) and (b) to appropriately size the vessel and avoid scaffold underexpansion. Devices were implanted following the manufacturer’s instructions for use. These recommendations included (a) lesion preparation: predilation of the entire diseased segment was performed either by cutting balloons or noncompliant balloons (balloon:artery ratio = 0.75:1.0) to optimize scaffold apposition and expansion; this was verified by IVUS, before BVS implantation ( Figure 2 ); (b) deployment: scaffolds were deployed by slow inflation (2 atm every 5 seconds) up to 12 to 14 atm; (c) positioning: multiscaffold inplantations were done with minimum overlapping (1 to 2 mm); and (d) postdilation: performed at operator’s discretion but respecting the described expansion limit of the implanted scaffold (0.5 mm more than the nominal scaffold diameter) with a shorter noncompliant balloon. Final postdilation was done with high-pressure non compliant balloon if residual stenosis post-absorb implantation was >20%. When acute procedural success was achieved (final in-scaffold residual stenosis of <30% and Thrombolysis In Myocardial Infarction [TIMI] flow 3 of the target site, without any complications), quantitative coronary angiography (QCA) was performed in 2 orthogonal projections. The result of this optimization was verified by OCT. OCT imaging technique was recommended because is superior in resolution compared with IVUS to verify immediate and long-term results of these new scaffolds.

Representative complex CTO case of the mid-right coronary artery treated with 2 overlapped Absorb-BVSs. Preprocedure angiography showed a long, calcified CTO lesion, without a clear stump, grade 3 on the J-CTO score of complexity (A) . After predilation with small balloons (B) , IVUS assessment was performed showing a moderately calcified lesion. Therefore, 2.5- and 3.0-mm cutting balloon predilation was performed.

Study definitions are provided in detail elsewhere. In short, according to the EuroCTO Club, “true” CTO was defined as the presence of TIMI 0 flow within the occluded segment with an estimated occlusion duration of >3 months. Acute procedural success was defined by final in-scaffold residual stenosis <30% and TIMI flow 3 in the target vessel. Acute device success was defined as successful delivery and deployment of study scaffolds at the intended target lesion and successful withdrawal of the delivery system, without the need for additional nonstudy stents.

QCA analysis was performed by an independent core laboratory (Barcelona Cardiac Imaging Core-Lab [BARCICORE-lab]) according to standard procedures, using dedicated software (CAAS, version 5.9; Pie Medical BV, Maastricht, The Netherlands). More detailed information on the QCA methodology has been previously described. In each patient, the treated segment and the peri-scaffold segments were analyzed QCA, in paired matched angiographic views after procedure and at 12 months follow-up ( Figures 3–10 ); 32 cases (including restenosis) had 12-month angiographic follow-up. Residual type B coronary dissections were allowed.

Multi-imaging follow-up after 2 Absorb-BVS scaffold implantations, 6-month MSCT (A) . Arrows indicate position of the radiopaque markers at the extremities of the scaffold and 12-month angiographic follow-up (B) after Absorb-BVS implantation.

OCT was performed (Dragonfly frequency domain OCT C7-XR System; St. Jude Medical, Plymouth, Minnesota) after the procedure and at 12 months. Off-line quantitative and qualitative analyses were performed by an independent core laboratory (BARCICORE-lab) with a dedicated software (St. Jude Medical). In each patient, the scaffold and peri-scaffold segments were analyzed by OCT ( Figures 4, 5, 8–11 ). More detailed information has been previously described. Scaffold incomplete apposition (ISA) was defined as a clear separation between the back (abluminal) side of the strut and the vessel wall with a distance larger than the strut thickness ( Figures 1 and 2, Supplementary data ).

Serial assessment of BVS by OCT. Coronary angiography and OCT (1 to 4) immediate postprocedure BVS implantation at the mid-right coronary artery. “*,” Indicate position of the radiopaque markers at the level of the overlap. No incomplete apposed struts were detected. (A) Coronary angiography 12 months after BVS implantation; 1 to 4 OCT assessment 12 months after BVS implantation. All the struts were covered by neointima (B) .

Representative easy CTO case with diffuse disease of the prox-mid and distal left anterior descending artery (LAD) treated with 4 overlapped Absorb-BVSs. LAD-CTO before PCI (A) . Immediate angiographic assessment after BVS implantation (B) . Immediate OCT assessment after BVS implantation (C) . MSCT at 7 months after BVS implantation in the mid-LAD. Arrows indicate position of the radiopaque markers at the extremities of the scaffold (D) . OCT assessment, 12 months after BVS implantation. All struts were covered by neointima (E) .

MSCT was performed using a 256-detector Philips Brilliance iCT System (Brilliance iCT; Philips Healthcare, Cleveland, Ohio). Data were analyzed on a dedicated workstation, Brilliance Workspace software (Cardiac Viewer Comprehensive Cardiac Analysis; Philips Healthcare). The scaffold and peri-scaffold segments were analyzed separately and in combination (in-segment analysis). Significant diameter stenosis was defined as ≥50% ( Figures 3, 5–8 , and 10 ).

Representative intermediate CTO case of the mid-right coronary artery (RCA) treated with 2 overlapped Absorb-BVSs. RCA-CTO before PCI (A) . Immediate angiographic assessment after BVS implantation (B) . MSCT at 6 months after BVS implantation at the RCA. Radiopaque markers are clearly visible at the extremities of the scaffold (C) . Angiographic assessment, 14 months after BVS implantation (D) .

MSCT at 6 months after 2 overlapped BVS implantations at the RCA. Radiopaque markers are clearly visible at the extremities of the scaffold (A and B) .

Angiographic and OCT (1 to 4) assessment 12 months after 2 BVS implantation of the mid RCA. All struts were well apposed and covered by neointima.

Representative complex CTO case of the ostial left anterior descending coronary artery treated with 1 Absorb-BVS. Preprocedure angiography of the CTO lesion (A and B) . OCT assessment after BVS implantation (C1 and C2) showed moderate acute recoil (C1).

MSCT at 8 months after BVS implantation at the LAD. Radiopaque markers are clearly visible at the extremities of the scaffold (A1 to A3). Angiographic assessment, 8 months after BVS implantation (B1 to B3).

Angiographic and OCT assessments 8 months after 1 BVS implantation of the LAD. All struts were well apposed and covered by neointima (1 to 3).

Blood tests for renal function, creatine kinase, and ultrasensitive troponin were performed pre- and at 6, 12, and 24 hours postprocedure. Clinical follow-up was scheduled at 1, 6, 12, and 18 months and 2, 3, 4, and 5 years; OCT was performed after BVS implantation and at 12 months, and MSCT was performed at baseline and at 6 months ( Figure 1 ).

Continuous variables are presented as mean and SD and categorical variables as number and percentage. Comparisons of continuous variables between groups were made using Student’s t test. Categorical variables were compared using either the chi-square or Fisher’s exact test. A p value <0.05 was considered to indicate statistical significance. Statistical analysis was performed using commercially available software (SPSS IBMS 21 for windows; SPPS IBM Inc., Chicago, Illinois).

Results

A total of 35 CTO lesions were prospectively included. Previously published detailed baseline clinical, lesion, and procedural characteristics are listed in Table 1 . In short, this registry comprised a relatively young population (mean age 61 ± 10 years) with stable symptoms of angina or silent ischemia at presentation (85%). After the J-CTO (Multicenter CTO registry of Japan) classification scheme, most lesions were classified as easy (25.6%) or intermediate difficult (48.7%). The decision to take an antegrade or retrograde approach was left to the operator, based on their personal experience and the lesion anatomy using preprocedure CT scan and angiography with simultaneous double injection when applicable. Final antegrade approach was used in 86% (n = 30) of cases, with single-wire technique in 31.4% (n = 11), wire escalation technique in 34.3% (n = 12), and double-wire technique in 20.0% (n = 7). The total number of guidewires used per lesion was 1.8 ± 1.1, being the Fielder XT (ASAHI Intecc Co., Ltd., Aichi, Japan) the most frequent guidewire used in 60% (n = 21). Predilation was undertaken in all cases, by cutting balloon in 71% and rotablator in 8.5%. IVUS analysis revealed subintimal scaffolding present in short segments of 2 complex cases. The total scaffolded length was 52.5 ± 22.8 mm per lesion. Postdilation was undertaken in 63% of lesions. All patients received dual antiplatelet therapy with aspirin and additional clopidogrel (85.7%) or ticagrelor (11.4%) or prasugrel (2.9%).

Clinical follow-up was completed at 6 and 12 months in 35 and 32 patients, respectively, with no major adverse cardiac events (MACE) or scaffold thrombosis ( Table 2 ). MSCT was performed in all cases at 6 months, with 2 cases of type IV scaffold restenosis per protocol definition. Both were confirmed by angiography at 12 months (n = 2, 6%). Both lesions were mid-circumflex and patients remained asymptomatic; according to patient and family decision, these patients did not undergo repeat revascularization. Table 3 lists the quantitative angiographic results. The mean reference diameter was 2.45 ± 0.46 mm, with a postprocedural residual stenosis of 9.23 ± 17.31%. In-scaffold late loss was −0.28 ± 0.31 mm with a diameter stenosis of 20.77 ± 12.16%.

Table 2

Short and mid-term outcomes

Outcomes	In-hospital Patients (n=33)/Lesions (n=35)	6 month FU Patients (n=33)/Lesions (n=35)	12 month FU Patients (n=33)/Lesions (n=35)
Acute procedural success	33 (100%)
Acute device success	35 (100%)
Cardiac Death	0	0	0
Q or Non-Q-Myocardial infarction	0 / 0	0 / 0	0 / 0
Target lesion revascularization	0	0	0
Major Adverse Cardiac Event (MACE)	0	0	0
Scaffold thrombosis	0	0	0
In- Scaffold restenosis	0	2 (6%) ∗	2 (6%) †

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