Abstract
Background/Objectives
Stent underexpansion is a risk factor for in-stent restenosis and stent thrombosis. Existing techniques to optimize stent expansion are sometimes ineffective. The aim of this study was to evaluate the effectiveness and feasibility of Excimer Laser Coronary Angioplasty (ELCA) in improving stent expansion when high-pressure non-compliant balloon inflation was ineffective.
Methods and Results
ECLA ablation was performed at high energy during contrast injection and only within the underexpanded stent. The primary endpoint of successful laser dilatation was defined as an increase of at least 1 mm 2 in minimal stent cross-sectional area (MSA) on IVUS or an increase of at least 20% in minimal stent diameter (MSD) by QCA, following redilatation with the same non-compliant balloon that had been unsuccessful prior to ELCA. Secondary endpoints were cardiac death, myocardial infarction (MI) and target lesion revascularization. Between June 2009 and November 2011, 28 patients with an underexpanded stent despite high-pressure balloon inflation were included. The mean laser catheter size was 1.2 ± 0.4 (range 0.9-2.0 mm) and a mean of 62 ± 12 mJ/mm 2 at 62 ± 21hertz were required for optimal expansion. Laser-assisted stent dilatation was successful in 27 cases (96.4%), with an improvement in MSD by QCA (1.6 ± 0.6 mm at baseline to 2.6 ± 0.6 mm post-procedure) and MSA by IVUS (3.5 ± 1.1 mm 2 to 7.1 ± 1.9 mm 2 ). Periprocedural MI occurred in 7.1%, transient slow-flow in 3.6% and ST elevation in 3.6%. During follow-up, there were no MIs, there was 1 cardiac-death, and TLR occurred in 6.7%.
Conclusions
The ELLEMENT study confirms the feasibility of ELCA with contrast injection to improve stent underexpansion in undilatable stented lesions.
1
Introduction
Calcific balloon-resistant coronary stenoses remain a technical challenge and an important cause of stent underexpansion, especially if adequate lesion preparation was not performed. Even in the drug-eluting stent era, stent underexpansion remains an important risk factor for in-stent restenosis (ISR) and stent thrombosis (ST) . Existing techniques to optimize stent expansion are often ineffective and can be harmful such as rotablation within an underexpanded stent which could be associated with serious complications . Implantation of another stent within an underexpanded stent is unlikely to correct the problem and will probably worsen what is primarily a mechanical problem, leading to recurrent restenosis or ST. Excimer laser coronary angioplasty (ELCA) has been previously reported to facilitate stent expansion in balloon-resistant lesions . It has been noted that the impact of ELCA on the surrounding tissue is dependent on the association with contrast media, saline and blood . In previous studies, the technique of saline “flush and bathe” was used in order to reduce the risk of coronary dissection induced by high-pressure waves . However, in patients with underexpanded stents, ELCA using a contrast or blood medium could assist the achievement of optimized expansion for these lesions by disrupting the underlying plaque . In this paper, we evaluated the usefulness of high-energy ELCA using contrast media, in patients with underexpanded stents resistant to high-pressure balloon inflation.
2
Methods
We enrolled 28 patients in this prospective, multi-center observational pilot study. In this registry, we included 3 patients with an underexpanded stent implanted in a de novo lesion and 25 patients with ISR lesions due to stent underexpansion despite the use of adequately sized non-compliant balloons at high pressure (≥ 18 atm). Patients presenting with acute MI and any lesions where no stent had been implanted before ELCA were excluded. All patients provided informed consent for both the procedure and subsequent data collection and analysis for research purposes.
2.1
Procedure
The procedure was performed according to standard techniques, with pre-procedural antiplatelet medication according to protocol. Intra-procedural heparin or bivalirudin use was per operator discretion. Glycoprotein 2b/3a administration was discouraged prior to ELCA. It was mandatory to perform pre-dilatation with a non-compliant balloon prior to ECLA of the target lesion. Once balloon underexpansion was found at angiography, intravascular ultrasound (IVUS) of the underexpanded stent was recommended if the lesion was crossable with the IVUS catheter. Calibration of the catheter was then performed and the desired energy level was set up. The ELCA catheter (Turbo Elite catheter®, 0.9 mm to 2.0 mm; Spectranetics Corporation, Colorado Springs, CO, USA) was passed over the guidewire, then inserted within the stent and advanced slowly toward the underexpanded zone. The catheter tip was maintained in close contact with the undilatable zone without necessarily crossing the lesion. The speed of this advancement was limited to 0.5 to 1.0 mm per second to avoid dotter effects, dissections and suboptimal ablation. Laser energy was applied in several trains of pulses of 3 to 5 seconds each. To maximize debulking, several passes are commonly performed. The procedure was then finalized by laser catheter removal and additional balloon and stent use according to standard practice.
Importantly, laser energy was never delivered outside the stent, particularly when contrast media was injected. The fluency and repetition rates were increased at the discretion of the operator but we advised that if optimal expansion of the lesion was not achieved, ELCA was to be performed with contrast injection at the highest fluency and repetition rates (i.e. 80 mJ/mm 2 and 80Hz for the 0.9 mm catheter).
2.2
Study endpoints and definitions
To determine if ELCA was effective in improving stent expansion, we defined success as an increase of at least 1 mm 2 for minimal stent cross-sectional area (CSA) as measured by IVUS; or an increase of at least 20% in minimal stent diameter (MSD) as measured by quantitative coronary angiography, when IVUS was not available. Coronary angiograms were analyzed offline using a validated edge detection system (CMS, version 5.2, MEDIS, The Netherlands) by an expert not involved in any of the procedures. Minimal stent diameter (MSD), reference vessel diameter, and percent diameter stenosis were measured at baseline and post-procedure. The endpoints to assess the safety of this novel procedure included: vessel perforation, dissection in an uncovered segment of the target vessel, slow-flow or no-reflow, and periprocedural myocardial infarction (MI). During follow-up, we also evaluated the occurrence of target lesion revascularization, MI, death, and ST. The standardized definitions of the Academic Research Consortium were applied for MI, revascularization, and ST .
2.3
Statistical analysis
Continuous variables are expressed as mean ± SD. Categorical variables are presented as absolute numbers and percentages. All analyses were conducted using SPSS software version 18.0. The authors had full access to and take full responsibility for the integrity of the data. All authors have read and agree to the manuscript as written.
2
Methods
We enrolled 28 patients in this prospective, multi-center observational pilot study. In this registry, we included 3 patients with an underexpanded stent implanted in a de novo lesion and 25 patients with ISR lesions due to stent underexpansion despite the use of adequately sized non-compliant balloons at high pressure (≥ 18 atm). Patients presenting with acute MI and any lesions where no stent had been implanted before ELCA were excluded. All patients provided informed consent for both the procedure and subsequent data collection and analysis for research purposes.
2.1
Procedure
The procedure was performed according to standard techniques, with pre-procedural antiplatelet medication according to protocol. Intra-procedural heparin or bivalirudin use was per operator discretion. Glycoprotein 2b/3a administration was discouraged prior to ELCA. It was mandatory to perform pre-dilatation with a non-compliant balloon prior to ECLA of the target lesion. Once balloon underexpansion was found at angiography, intravascular ultrasound (IVUS) of the underexpanded stent was recommended if the lesion was crossable with the IVUS catheter. Calibration of the catheter was then performed and the desired energy level was set up. The ELCA catheter (Turbo Elite catheter®, 0.9 mm to 2.0 mm; Spectranetics Corporation, Colorado Springs, CO, USA) was passed over the guidewire, then inserted within the stent and advanced slowly toward the underexpanded zone. The catheter tip was maintained in close contact with the undilatable zone without necessarily crossing the lesion. The speed of this advancement was limited to 0.5 to 1.0 mm per second to avoid dotter effects, dissections and suboptimal ablation. Laser energy was applied in several trains of pulses of 3 to 5 seconds each. To maximize debulking, several passes are commonly performed. The procedure was then finalized by laser catheter removal and additional balloon and stent use according to standard practice.
Importantly, laser energy was never delivered outside the stent, particularly when contrast media was injected. The fluency and repetition rates were increased at the discretion of the operator but we advised that if optimal expansion of the lesion was not achieved, ELCA was to be performed with contrast injection at the highest fluency and repetition rates (i.e. 80 mJ/mm 2 and 80Hz for the 0.9 mm catheter).
2.2
Study endpoints and definitions
To determine if ELCA was effective in improving stent expansion, we defined success as an increase of at least 1 mm 2 for minimal stent cross-sectional area (CSA) as measured by IVUS; or an increase of at least 20% in minimal stent diameter (MSD) as measured by quantitative coronary angiography, when IVUS was not available. Coronary angiograms were analyzed offline using a validated edge detection system (CMS, version 5.2, MEDIS, The Netherlands) by an expert not involved in any of the procedures. Minimal stent diameter (MSD), reference vessel diameter, and percent diameter stenosis were measured at baseline and post-procedure. The endpoints to assess the safety of this novel procedure included: vessel perforation, dissection in an uncovered segment of the target vessel, slow-flow or no-reflow, and periprocedural myocardial infarction (MI). During follow-up, we also evaluated the occurrence of target lesion revascularization, MI, death, and ST. The standardized definitions of the Academic Research Consortium were applied for MI, revascularization, and ST .
2.3
Statistical analysis
Continuous variables are expressed as mean ± SD. Categorical variables are presented as absolute numbers and percentages. All analyses were conducted using SPSS software version 18.0. The authors had full access to and take full responsibility for the integrity of the data. All authors have read and agree to the manuscript as written.
3
Results
Between June 2009 and March 2011, 28 patients with an underexpanded stent despite high-pressure balloon inflation were included. The mean age was 71.5 ± 10.5 years, 19 patients (67.9%) were male, and diabetes mellitus was present in 12 patients (42.9%). Seven patients (25.0%) presented with unstable angina ( Table 1 ). Target lesions occurred in the following coronary arteries: 1 (3.6%) in the distal left main, 15 (53.6%) in left anterior descending artery, 6 (21.5%) in left circumflex, 5 (17.9%) in right coronary artery and 1 in a saphenous vein graft. In patients with restenotic lesions, index procedures were performed successfully in all patients. The mean stent size was 3.2 ± 0.4 mm and postdilatation was performed using a 3.3 ± 0.5 mm non-compliant balloon at 22.8 ± 4.8 atm. The mean catheter size was 1.2 ± 0.4 (range 0.9-2.0 mm) and a mean fluency of 62 ± 12 mJ/mm 2 at 62 ± 21 Hz were required for optimal expansion. Rotational atherectomy was performed in 2 patients (7.1%) and cutting balloon in 1 patient (3.6%) before ELCA treatment. IVUS was performed in 21 (75%) patients ( Table 2 ). However, in 4 patients (14.2%), it was not possible to advance the IVUS catheter through the lesion before ELCA. In all patients, expansion of the stent with a non-compliant balloon at high pressure was attempted before ELCA and with the same balloon after ELCA.
| n = 28 | |
|---|---|
| Age (years) | 71.5 ± 10.5 |
| Male gender | 19 (67.9) |
| LVEF | 49.0 ± 10.5 |
| Previous MI | 14 (50.0) |
| Previous CABG | 9 (32.1) |
| Previous PCI | 26 (92.9) |
| Diabetes Mellitus | 12 (42.9) |
| Hypertension | 21 (75.0) |
| Dyslipidemia | 14 (50.0) |
| Smoker | 4 (14.3) |
| Unstable angina | 7 (25.0) |
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