Abstract
Background
There is limited information on optical coherence tomography (OCT) findings after percutaneous coronary intervention (PCI) of chronic total occlusions (CTOs). OCT allows high resolution imaging that can enhance understanding of the vascular response after stenting of chronically occluded vessels.
Methods
The Angiographic Evaluation of the Everolimus-Eluting Stent in Chronic Total Occlusions (ACE-CTO) study collected angiographic and clinical outcomes from 100 patients undergoing CTO PCI with the everolimus-eluting stent (EES). OCT was performed 8-months post stenting in 62 patients. Every third frame was analyzed throughout the course of the stented arterial segment. Lumen contours were semi-automatically traced and stent struts were manually delineated, with automatic measurement of the strut to lumen distance. Struts on the luminal side of the lumen contour were classified as malapposed if the distance to the lumen contour exceeded 0.108 mm.
Results
A total of 44,450 struts in 6047 frames were analyzed, of which 4113 9.3%, 95% confidence intervals [CI] 9.0% to 9.5%) were malapposed and 1230 (2.8%, 95% CI 2.6% to 2.9%) were uncovered. Fifty-five of 62 patients (88.7%, 95% CI 78.5% to 98.4%) had at least one malapposed stent strut and 50 patients (80.7%, 95% CI 69.2% to 88.6%) had at least one uncovered stent strut. Mean strut-intimal thickness of the apposed and malapposed struts was 0.126 ± 0.140 mm and − 0.491 ± 0.440 mm, respectively.
Conclusion
High rates of stent strut malapposition and incomplete stent strut coverage were observed after CTO PCI using EES, highlighting unique challenges associated with stent implantation in CTOs.
Highlights
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Percutaneous coronary intervention with drug-eluting stents for chronic total occlusion is associated with a 40% rate of binary in-stent restenosis at 8 months
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Of patients who receive a drug eluting stent for a chronic total occlusion 88.7% will have stent strut malapposition and 80.7% will have incomplete strut coverage on follow-up
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Target lesion revascularization occurred in 39% of patients who underwent revascularization for a chronic total occlusion at 8 months
1
Introduction
Percutaneous coronary intervention (PCI) of coronary chronic total occlusions (CTOs) has been associated with higher restenosis rates compared with non-CTO lesions . Potential explanations include diffuse vessel disease, negative remodeling of the target vessel due to prolonged hypoperfusion, long stent length (full metal jacket) , and stenting within subintimal vessel segments, however there is limited data on the mechanisms underlying long-term stent failure after CTO PCI.
Due to its high resolution, optical coherence tomography (OCT) can provide unique insights into the mechanisms of stent thrombosis and in-stent restenosis, allowing accurate assessment of stent malapposition and stent coverage. The AngiographiC Evaluation of the Everolimus-Eluting Stent in Chronic Total Occlusions (ACE-CTO) study ( NCT01012869 ) demonstrated high restenosis rates among patients undergoing PCI with everolimus-eluting stents (EES) of unselected complex CTO lesions . After its introduction in clinical practice in 2010, OCT imaging was added to the follow-up protocol of the ACE-CTO study patients to provide insights into the healing process and mechanisms of failure after stenting of CTOs.
2
Methods
2.1
Study design
ACE-CTO was a single-center, single-arm, non-randomized, open label, prospective study that evaluated outcomes after implantation of EES in coronary CTOs . Inclusion criteria were: (a) age ≥ 18 years; (b) successful treatment of a native coronary artery CTO (defined as a lesion with 100% angiographic stenosis that was at least 3 months old, as estimated by clinical information, sequential angiographic information, or both) using everolimus-eluting stents; (c) ability and willingness to return for angiographic follow-up after 8 months and to be followed clinically for 12 months; and (d) agreement to participate and provide informed consent. Exclusion criteria were: (a) planned non-cardiac surgery within the following 12 months; (b) recent positive pregnancy test, breast-feeding, or possibility of a future pregnancy; (c) coexisting conditions that limit life expectancy to less than 12 months; (d) creatinine above 2.5 mg/dL (unless patients required hemodialysis, in which case they were eligible to participate); and (e) history of an allergic reaction or significant sensitivity to everolimus. Treatment strategy of the target CTO lesion was at the discretion of the operator. All eligible consecutive patients were asked to participate in the study. The study was approved by the institutional review board and all patients provided written informed consent.
2.2
Study protocol
All study patients were followed by phone at 1, 6, and 12 months and were asked to return for follow-up angiography and intravascular ultrasonography at 8 months post stent implantation. The primary endpoint of the ACE-CTO study was the 8-month incidence of binary angiographic restenosis. Dual antiplatelet therapy was prescribed for at least 12 months. After introduction of OCT in clinical practice, the study protocol was modified to include OCT evaluation at the time of follow-up angiography.
2.3
Optical coherence tomography.
At 8 months post-stenting, intracoronary OCT imaging of the target vessel stented segment was successfully performed in 62 patients using a C7XR FD-OCT Imaging System (St Jude Medical, Minneapolis, Minnesota) with a 2.7Fr OCT catheter after intracoronary administration of 200 mcg of nitroglycerin. OCT images were transferred to a Lightlab Imaging Offline Review Workstation for strut-level analysis. All analyses were realized by a single operator who received thorough training in measurement and analysis of OCT data. Every third frame was analyzed throughout the course of the stented arterial segment. Frames with significant artifact or major side branches limiting analysis were excluded. Lumen contours were semi-automatically traced and stent struts were manually delineated, with automatic measurement of the distance from the strut to the lumen contour, (strut-intimal thickness [SIT]). Struts on the luminal side of the lumen contour had negative SIT values, while struts on the intimal side of the lumen contour had positive SIT values. Struts with SIT <−0.108 mm [the sum of strut + polymer thickness along with a correction for the limit of resolution of OCT ] were classified as malapposed; all other struts were classified as apposed. Each strut was classified as either covered with tissue or uncovered based on visual appearance . Percent strut malapposition and incomplete stent strut coverage per patient was defined as the number of malapposed or incompletely covered struts, respectively, in each patient divided by the total number of struts in the same patient, multiplied by 100. Aneurysm was defined as localized dilatation exceeding the diameter of adjacent normal segment by 50% .
2.4
Statistical analyses
Continuous parameters were presented as mean ± standard deviation and compared using the t-test, one-way analysis of variance (ANOVA) or the Wilcoxon rank-sum test, as appropriate. Nominal parameters were presented as percentages and compared using the Pearson’s chi-square or the Fisher’s exact test, as appropriate. All analyses were performed with JMP version 11.0 (SAS Institute, Cary, North Carolina).
2
Methods
2.1
Study design
ACE-CTO was a single-center, single-arm, non-randomized, open label, prospective study that evaluated outcomes after implantation of EES in coronary CTOs . Inclusion criteria were: (a) age ≥ 18 years; (b) successful treatment of a native coronary artery CTO (defined as a lesion with 100% angiographic stenosis that was at least 3 months old, as estimated by clinical information, sequential angiographic information, or both) using everolimus-eluting stents; (c) ability and willingness to return for angiographic follow-up after 8 months and to be followed clinically for 12 months; and (d) agreement to participate and provide informed consent. Exclusion criteria were: (a) planned non-cardiac surgery within the following 12 months; (b) recent positive pregnancy test, breast-feeding, or possibility of a future pregnancy; (c) coexisting conditions that limit life expectancy to less than 12 months; (d) creatinine above 2.5 mg/dL (unless patients required hemodialysis, in which case they were eligible to participate); and (e) history of an allergic reaction or significant sensitivity to everolimus. Treatment strategy of the target CTO lesion was at the discretion of the operator. All eligible consecutive patients were asked to participate in the study. The study was approved by the institutional review board and all patients provided written informed consent.
2.2
Study protocol
All study patients were followed by phone at 1, 6, and 12 months and were asked to return for follow-up angiography and intravascular ultrasonography at 8 months post stent implantation. The primary endpoint of the ACE-CTO study was the 8-month incidence of binary angiographic restenosis. Dual antiplatelet therapy was prescribed for at least 12 months. After introduction of OCT in clinical practice, the study protocol was modified to include OCT evaluation at the time of follow-up angiography.
2.3
Optical coherence tomography.
At 8 months post-stenting, intracoronary OCT imaging of the target vessel stented segment was successfully performed in 62 patients using a C7XR FD-OCT Imaging System (St Jude Medical, Minneapolis, Minnesota) with a 2.7Fr OCT catheter after intracoronary administration of 200 mcg of nitroglycerin. OCT images were transferred to a Lightlab Imaging Offline Review Workstation for strut-level analysis. All analyses were realized by a single operator who received thorough training in measurement and analysis of OCT data. Every third frame was analyzed throughout the course of the stented arterial segment. Frames with significant artifact or major side branches limiting analysis were excluded. Lumen contours were semi-automatically traced and stent struts were manually delineated, with automatic measurement of the distance from the strut to the lumen contour, (strut-intimal thickness [SIT]). Struts on the luminal side of the lumen contour had negative SIT values, while struts on the intimal side of the lumen contour had positive SIT values. Struts with SIT <−0.108 mm [the sum of strut + polymer thickness along with a correction for the limit of resolution of OCT ] were classified as malapposed; all other struts were classified as apposed. Each strut was classified as either covered with tissue or uncovered based on visual appearance . Percent strut malapposition and incomplete stent strut coverage per patient was defined as the number of malapposed or incompletely covered struts, respectively, in each patient divided by the total number of struts in the same patient, multiplied by 100. Aneurysm was defined as localized dilatation exceeding the diameter of adjacent normal segment by 50% .
2.4
Statistical analyses
Continuous parameters were presented as mean ± standard deviation and compared using the t-test, one-way analysis of variance (ANOVA) or the Wilcoxon rank-sum test, as appropriate. Nominal parameters were presented as percentages and compared using the Pearson’s chi-square or the Fisher’s exact test, as appropriate. All analyses were performed with JMP version 11.0 (SAS Institute, Cary, North Carolina).
3
Results
3.1
Patient characteristics and outcomes
The baseline clinical and angiographic characteristics of the 62 patients included in the present analysis are summarized in Tables 1 and 2 . Patients had high prevalence of diabetes mellitus, prior PCI and prior coronary artery bypass graft surgery (CABG) and most often presented with stable angina. The right coronary artery was the most common CTO target vessel and all contemporary CTO PCI techniques (antegrade wire escalation, antegrade dissection/re-entry, and retrograde) were utilized for recanalization. Mean stent length was 86 ± 37 mm and the peak stent dilation pressure was 20 ± 5 atm. Patient characteristics were matched between lesions with high and low prevalence of malapposed stent struts, and the two lesion groups had similar baseline angiographies and J-CTO scores ( Table 1 ). Procedural factors including number of stents used, stent length and degree of overlap did not significantly affect future stent apposition and coverage ( Table 2 ).
| Variable | All patients (n = 62) | Patients with predominantly malapposed struts ⁎ (n = 31) | Patients with predominantly non-malapposed struts ⁎ (n = 31) | p |
|---|---|---|---|---|
| Age (years) | 65 ± 6 | 65 ± 6 | 65 ± 6 | 0.87 |
| Men (%) | 98 | 97 | 100 | > 0.99 |
| Current smoking (%) | 32 | 42 | 23 | 0.10 |
| Hypertension (%) | 90 | 97 | 84 | 0.20 |
| Hyperlipidemia (%) | 87 | 94 | 81 | 0.26 |
| Diabetes mellitus (%) | 42 | 39 | 45 | 0.61 |
| Prior MI (%) | 48 | 58 | 39 | 0.13 |
| Prior CABG (%) | 32 | 39 | 26 | 0.28 |
| Prior stroke (%) | 8 | 10 | 6 | > 0.99 |
| Prior PCI (%) | 18 | 16 | 19 | 0.74 |
| Presentation | ||||
| Stable angina (%) | 95 | 97 | 93 | 0.60 |
| ACS (%) | 2 | 0 | 3 | |
| Other (%) | 3 | 3 | 4 | |
| Medications | ||||
| Aspirin (%) | 97 | 97 | 97 | > 0.99 |
| Clopidogrel (%) | 55 | 61 | 48 | 0.31 |
| Statin (%) | 90 | 97 | 84 | 0.20 |
| Beta blocker (%) | 84 | 90 | 77 | 0.30 |
| Nitrates (%) | 56 | 65 | 48 | 0.20 |
| Calcium channel blocker (%) | 21 | 19 | 23 | 0.76 |
| CTO target vessel | ||||
| RCA (%) | 74 | 84 | 63 | 0.14 |
| LAD (%) | 15 | 6 | 23 | |
| LCX (%) | 11 | 10 | 13 | |
| Moderate/Severe tortuosity (%) | 26 | 26 | 26 | 0.87 |
| Moderate/Severe calcification (%) | 76 | 87 | 65 | 0.07 |
| J-CTO score | 2.1 ± 1.1 | 2.1 ± 1.0 | 2.1 ± 1.2 | > 0.99 |
| J-CTO | 0.65 | |||
| 0 (%) | 10 | 10 | 10 | |
| 1 (%) | 15 | 10 | 19 | |
| 2 (%) | 45 | 52 | 39 | |
| ≥ 3 (%) | 31 | 29 | 32 |
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