Abstract
Objective
The objective is to see if use of the ACIST™ device during carotid stenting would be feasible without an increase in primary end points when compared to historic controls.
Background
Carotid stenting has been studied as an effective alternative to endarterectomy in high-surgical-risk patients. Traditional angiography involves manual contrast injection. It leads to excess contrast volume and greater fluoroscopy times. The Acist contrast injection device helps with the regulation and lowering of contrast volume.
Methods
This is a consecutive, non-randomized, open-label, multiple-operator-based study. Inclusion criteria were as follows: (a) subject is considered at high risk for carotid endarterectomy, (b) subject requires percutaneous carotid angioplasty and stenting for carotid disease, and (c) subject must be asymptomatic with ≥ 80% stenosis of the internal and/or common carotid artery. The primary end points measured were, death from any cause, myocardial infarction, transient ischemic attack or stroke within 30 days of intervention. Secondary end points were contrast volume and fluoroscopy time.
Results
Four operators in one institution performed interventions from June 2007 to May 2012 on 133 consecutive patients. They were predominantly men (59.4%). The mean age (SD) was 73.64 (7.952) years. Stroke occurred in 3% ( N = 4), transient ischemic attack in 0.8% ( N = 1) and myocardial infarction in 0.8% ( N = 1). Three study subjects died (2.3%). The mean (SD) contrast volume was 121.24 (67.79) mL. The mean (SD) fluoroscopy time was 18.34 (11.31) minutes.
Conclusions
The use of the ACIST™ device was feasible in carotid stenting in a high-risk population without an increase in end points when compared to historic controls.
1
Introduction
Asymptomatic patients with > 80% carotid stenosis are at stroke risk of 3%–5% per year . The two common modalities of treatment for carotid stenosis are carotid endarterectomy (CEA) and carotid artery stenting (CAS)/angioplasty. Multiple studies have been performed comparing surgery with stenting. Risks like compression of stent and plaque embolization to the brain were limiting factors for carotid stenting until some time ago . However, even high-surgical-risk patients would still undergo endarterectomy in routine practice and had significantly worse complications than reported . With the advent of improved stents and embolic protection devices, carotid stenting is now being done more often than previously for high-surgical-risk patients. Global registry data have shown that the rate of stroke and deaths related to the procedure was previously 5.29% in the pre-embolic device era and has fallen to 2.23% currently with the use of embolic protection . Embolic devices have been shown to significantly reduce the incidence of cerebral ischemic events from 5.5% to 1.8% . The ARCHeR (Acculink for Revascularization of Carotids in High Risk Patients) study has shown that carotid stenting with embolic protection devices was not inferior to endarterectomy and was an effective alternative to prevent stroke in high-surgical-risk patients .
Manual contrast injection is physician regulated and could lead to excess contrast volume use and greater fluoroscopy times with an increase in radiation exposure . The ACIST™ device (Advanced Contrast Imaging System Technology, Eden Prairie, Minnesota, USA) is a software-controlled, variable rate, self-purging injection device used to deliver contrast. It can help in adequate regulation and lowering of the contrast volume . The objective of our study is to see if use of this device during carotid stenting would be feasible without an increase in primary end points of death, myocardial infarction, transient ischemic attack (TIA) or stroke within 30 days of intervention when compared to historic controls.
2
Methods
This is a non-randomized, consecutive, open-label, multiple-operator-based, safety/efficacy study. The Choice registry is an industry-funded study (Abbott Vascular, Inc.) and all patients were part of the registry and the study protocol was designed by Abbott Vascular. All patients gave written informed consent. A total of 133 consecutive patients were enrolled in one institution. The procedures were performed by four operators between June 2007 and May 2012. In addition to the interventionists, the center was assisted with a neurologist, vascular and cardiothoracic surgeon and a research coordinator. We included high-risk patients with multiple co-morbid conditions as an alternative to carotid endarterectomy. All patients were asymptomatic before the procedure without any transient ischemic attack or stroke related to the study carotid artery within 6 months before the procedure.
Inclusion criteria were as follows: (a) subject is considered at high risk for carotid endarterectomy, (b) subject requires percutaneous carotid angioplasty and stenting for carotid artery disease, and (c) subject must be asymptomatic with ≥ 80% stenosis of the internal and/or common carotid artery by ultrasound or angiogram. There were no exclusion criteria. None of the patients had any contraindications to the intended procedure. American Stroke Association (ASA) class and risk level were documented on the pre-procedure evaluation. Procedure site identification was completed and documented and site marked according to policy. Surgical team “time out” for site identification was documented in all cases.
Embolic protection device was used successfully in all patients. The ACIST™ device was used for contrast injection in all patients and carotid stenting successfully performed. The stent used in procedure was the RX ACCULINK® (Abbott Vascular, Santa Clara, California, USA) in all patients. The patients in the study received Bivalirudin (The Medicines Company, Parsippany, New Jersey, USA) per current standard of care guidelines. Aspirin and clopidogrel (Bristol-Myers Squibb, New York, USA) were started at least 3 days before the procedure. All patients were recommended to continue aspirin for life and clopidogrel for at least 4 weeks after the procedure.
As part of the study, all patients had an independent NIHSS (National Institute of Health Stroke Scale) scoring system performed prior to, after the procedure and at a 30-day follow-up. Following the procedure they were reassessed in less than 24 hours and daily until discharged home. At 30-day follow-up visit, all patients underwent a physical exam by the interventional cardiologist and a neurocertified registered nurse.
Stroke was defined as an acute neurological manifestation from cerebral ischemia with focal symptoms and signs lasting for more than 24 hours. TIA was defined as an acute neurological manifestation with focal symptoms and signs lasting less than 24 hours. Q-wave myocardial infarction was defined as the development of pathological Q waves in two or more leads. Non-Q-wave myocardial infarction was defined as elevation of CK levels to greater than three times the upper limit of normal in the presence of elevated CK-MB (greater than the upper limit of normal) and in the absence of new pathological Q waves in two or more leads.
We described the demographic characteristics of the study population using simple descriptive statistics. The primary end points studied were the frequency of death from any cause, myocardial infarction, transient ischemic attack or stroke within 30 days of intervention. Secondary end points measured were mean contrast volume and fluoroscopy time. Data were analyzed with SPSS 19.0 software (SPSS Inc., Chicago, IL). The study was approved by the Western Institutional Review Board (WIRB, Olympia, Washington).
2
Methods
This is a non-randomized, consecutive, open-label, multiple-operator-based, safety/efficacy study. The Choice registry is an industry-funded study (Abbott Vascular, Inc.) and all patients were part of the registry and the study protocol was designed by Abbott Vascular. All patients gave written informed consent. A total of 133 consecutive patients were enrolled in one institution. The procedures were performed by four operators between June 2007 and May 2012. In addition to the interventionists, the center was assisted with a neurologist, vascular and cardiothoracic surgeon and a research coordinator. We included high-risk patients with multiple co-morbid conditions as an alternative to carotid endarterectomy. All patients were asymptomatic before the procedure without any transient ischemic attack or stroke related to the study carotid artery within 6 months before the procedure.
Inclusion criteria were as follows: (a) subject is considered at high risk for carotid endarterectomy, (b) subject requires percutaneous carotid angioplasty and stenting for carotid artery disease, and (c) subject must be asymptomatic with ≥ 80% stenosis of the internal and/or common carotid artery by ultrasound or angiogram. There were no exclusion criteria. None of the patients had any contraindications to the intended procedure. American Stroke Association (ASA) class and risk level were documented on the pre-procedure evaluation. Procedure site identification was completed and documented and site marked according to policy. Surgical team “time out” for site identification was documented in all cases.
Embolic protection device was used successfully in all patients. The ACIST™ device was used for contrast injection in all patients and carotid stenting successfully performed. The stent used in procedure was the RX ACCULINK® (Abbott Vascular, Santa Clara, California, USA) in all patients. The patients in the study received Bivalirudin (The Medicines Company, Parsippany, New Jersey, USA) per current standard of care guidelines. Aspirin and clopidogrel (Bristol-Myers Squibb, New York, USA) were started at least 3 days before the procedure. All patients were recommended to continue aspirin for life and clopidogrel for at least 4 weeks after the procedure.
As part of the study, all patients had an independent NIHSS (National Institute of Health Stroke Scale) scoring system performed prior to, after the procedure and at a 30-day follow-up. Following the procedure they were reassessed in less than 24 hours and daily until discharged home. At 30-day follow-up visit, all patients underwent a physical exam by the interventional cardiologist and a neurocertified registered nurse.
Stroke was defined as an acute neurological manifestation from cerebral ischemia with focal symptoms and signs lasting for more than 24 hours. TIA was defined as an acute neurological manifestation with focal symptoms and signs lasting less than 24 hours. Q-wave myocardial infarction was defined as the development of pathological Q waves in two or more leads. Non-Q-wave myocardial infarction was defined as elevation of CK levels to greater than three times the upper limit of normal in the presence of elevated CK-MB (greater than the upper limit of normal) and in the absence of new pathological Q waves in two or more leads.
We described the demographic characteristics of the study population using simple descriptive statistics. The primary end points studied were the frequency of death from any cause, myocardial infarction, transient ischemic attack or stroke within 30 days of intervention. Secondary end points measured were mean contrast volume and fluoroscopy time. Data were analyzed with SPSS 19.0 software (SPSS Inc., Chicago, IL). The study was approved by the Western Institutional Review Board (WIRB, Olympia, Washington).
3
Results
We included a total of 133 consecutive patients at our institution. Four operators performed interventions from June 2007 to May 2012. They were predominantly men (59.4%). The mean age was 73.64 years with a standard deviation (SD) of 7.952 years. The primary end points were measured within 30 days of intervention. Stroke occurred in 3% ( N = 4), transient ischemic attack in 0.8% ( N = 1) and myocardial infarction in 0.8% ( N = 1). Three study subjects died (2.3%). The mean (SD) contrast volume was 121.24 (67.79) mL. The mean (SD) fluoroscopy time was 18.34 (11.31) minutes.
4
Discussion
The traditional method of performing coronary/vascular angiography involves repetitive manipulation of a stopcock-manifold system and hand syringe injections of contrast. The limitations include involvement of multiple assistants to help with the catheterization devices, syringe manipulations and lack of a regulated contrast amount . The traditional method also involves using a standard power injection using ANGIOMAT-6000® (Liebel-Flarsheim, Cincinnati, Ohio, USA) for left ventriculography. Over the years many mechanical injectors have been studied to overcome these limitations. However, power injectors which deliver fixed contrast have not gained widespread acceptance as operators still prefer to control speed and volume of contrast delivery manually.
The ACIST™ medical systems (Eden Prairie, Minnesota, USA) developed a software-controlled variable rate, self-purging syringe injector (ACIST™ device) which has been studied well for coronary catheterization. Its four integrated components include a software-controlled syringe injector, disposable automated manifold without stopcocks, disposable hand controller and a touch screen control panel . The automated manifold enables switching between contrast and saline injection and allows hemodynamic monitoring except during injection of contrast . The touch screen control takes over the work of the manual syringe hence giving freedom to the interventionist’s hands to take care of the primary catheterization devices. A potential advantage of the ACIST device is that, once connected, the closed system reduces the chance for manually injecting air through operator error.
The automated injection allows efficient contrast dosing thereby reducing contrast risks, radiation exposure and ultimately cost . It is more efficient than the manual technique in procedure room workflow and saves time as well as contrast . The device was shown to significantly reduce the total amount of contrast media, fluoroscopy time in both diagnostic and interventional catheterization . The image quality was found to be equivalent between the manual and “Acist” technique . The use of the device allowed lesser amount of contrast, both used and total contrast, for diagnostic and/or percutaneous coronary intervention when compared with the manual technique .
The ACIST™ device also facilitates smaller catheter use for effective interventions. Four-French catheter use with the device has been compared with 6 Fr utilizing the manual technique and with earlier ambulation noted . The use of smaller catheters without compromising image quality would indirectly cause less use of closure devices which facilitates early ambulation and discharge . Even when same-sized smaller catheters (4 Fr) were used and compared between both techniques, the angiographic image quality was equivalent with significantly less contrast volume with the automated injection technique than the manual technique .
The ACIST™ device has been used for some time with carotid stenting, but there have been no published reports of its use. Carotid angiography is somewhat similar to coronary angiography regarding techniques and manipulations. The complications are however different but those regarding excess use of contrast are similar. Patients with carotid disease are usually similar in demographics to patients with coronary disease in whom contrast-induced nephropathy has been extensively studied . The same renal protection measures should be taken in carotid stenting used to prevent contrast-induced nephropathy. The average or mean contrast volume in CAS has not been well reported and there are no randomized controlled trials or adequate reports on this data. Very few studies like the one done by Kato et al. , have mentioned the mean contrast volume and mean contrast ratio, which were 147.3 ± 48.3 mL and 0.57 ± 0.32 mL, respectively. Since the ACIST™ device is known to produce equivalent quality image with less contrast, we attempted to study carotid stenting with use of this device and compare it with historic controls where manual injections were used.
The average fluoroscopy time for high-risk carotid interventions is unknown as there has been no systematic documentation historically. Prolonged fluoroscopy times usually indicate difficult interventions and have been associated with a higher incidence of neurological complications . Madhwal et al. showed that prolonged fluoroscopy times during carotid stenting are related to the distance from the origin of the target artery to the beginning of the descending aorta, and to the tortuosity of the target vessel. In their study, the difficult CAS cases had a median fluoroscopy time of 58 minutes and the easy CAS group 19 minutes. The severity of stenosis did not affect the fluoroscopy time. Our study which includes all high-risk patients showed a mean lower than the median fluoroscopy time of their easy CAS group. This could be due to the operators experience in our study. It has been shown in studies that the learning curve improves significantly with the number of endovascular procedures . Improved performance on the Vascular Interventional System Trainer simulator when comparing first and last simulations has been demonstrated .
4.1
Comparisons
Although comparisons are hard to make between different trials we attempted to get a synopsis of the results of relevant trials. If one evaluates the CREST (Carotid Revascularization Endarterectomy versus Stenting Trial) trial and considers the carotid stenting group in that study for primary events in the peri-procedural period (30 days from intervention), the total stroke rate was 4.01%, myocardial infarction rate was 0.99% and death rate was 0.7% . But all patients in the CREST trial were not considered high-risk category patients whereas our study had only high-risk patients. The SAPPHIRE (Stenting and Angioplasty with Protection in Patients at High-Risk for endarterectomy) trial had high-risk patients and included both symptomatic and asymptomatic patients . In the asymptomatic group, the cumulative incidence of the three primary events was 5.4%. The BEACH (Boston Scientific Embolic Protection, Inc. [EPI]: A Carotid Stenting Trial for High-Risk Surgical Patients) trial , the CABERNET (Carotid Artery revascularization using the Boston Scientific FilterWire EX®/EZ™ and the EndoTex™ NexStent®) trial , the MAVErICK (Medtronic AVE Self expanding Carotid Stent System with distal protection in the treatment of Carotid stenosis) 1 and 2 trials , the ARCHeR study , the ARMOUR (Proximal Protection with the MO.MA Device during Carotid Stenting) study , are some of the other trials (see Table 1 for comparative analysis) and when compared with these high-risk studies, our results are definitely comparable both in success and in complications.
