Optical Imaging Measurement of Intravascular Solution Efficacy Trial

Study Overview
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Brief Summary
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Iodinated contrast is the current gold standard for infrainguinal angiography imaging in patients without renal insufficiency and has also been used with intravascular Optical Coherence Tomography (iOCT) to improve image quality in human coronary arteries as well as carotid arteries. The current debate in the literature for iOCT medium is between iodinated contrast and dextran and CO2 may offer a superior method of iOCT imaging during lower extremity occlusive disease interventions. The investigators hypothesize that the CO2 medium injection during iOCT data acquisition is feasible and will produce at least the same quality of imaging as that obtained with contrast or dextran without causing the problems of volume overload and renal toxicity seen with the two latter mediums. Primary Outcomes Measured Quality: Cumulative number of clear image frame (CIF) through the entire 54mm length segment. Quantitative: Calculations of the area and diameter of each segment will be measured to determine if index of refraction has any effect between the three mediums to be tested. The investigators expect to find little difference between all three iOCT mediums and hope to conclude that CO2 offers a superior side effect profile for iOCT imaging in the lower extremity arterial system.

Detailed Description
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Peripheral artery disease (PAD) affects anywhere from 8-12 Million people in the United States. Many of these people go on to develop claudication, rest pain, and tissue loss. During the workup for these disease states many imaging modalities are conducted including Pulse Volume Recording, Duplex Ultrasound, Angiography, and IVUS, but an emerging catheter based imaging has been developed that may supplement the current modalities used. Intravascular optical coherence tomography (iOCT) is based on near-infrared light system. The light reflects off plaque and other objects within vessels and the signals are processed into a series of axial images (A-scans) at different positions along the artery to generate a two-dimensional dataset (B-scans). These images are created at an extremely fine resolution of 10-15 μm, which has allowed iOCT to be used in many research settings including PAD and coronary artery disease. OCT has been approved for clinical use in the coronary territory by the FDA in May 2010. Since then many centers have been using iOCT in the daily clinical practice. However, it's still not widely in the clinical management of patients with PAD. There is hope that the high resolution capabilities of iOCT may help before and after an intervention to predict outcomes or correct errors in stent deployment. The iOCT procedure for lower extremity PAD is fairly straightforward. An introducer is placed into the femoral artery. After which a wire is placed past the lesion of interest and the iOCT catheter is inserted. The catheter is then attached to an automated pullback device. Next an optical medium is needed to displace the erythrocytes. Due to the high resolution of the iOCT this is necessary for a cleaner image to analyze. At the time of injection of the optical medium a sensor triggers the catheter to be withdrawn (distal to proximal) at anywhere from 10-25 mm/sec. The images are captured and processed and arterial plaque can be characterized. The greatest strength of the iOCT catheter is its high resolution images but the problem is that the imaging signal is substantially attenuated by blood. In order to remedy this complication techniques such as proximal balloon occlusion and continuous infusion of a fluid have been used to acquire improved iOCT images. In the continuous infusion methods, different mediums have been injected such as contrast, dextran, and even an oxygen-carrying substitute in hopes of improving decreasing the attenuation by blood. In order the overcome the attenuation of red blood cells during iOCT imaging, we are proposing a novel approach involving CO2 injection to clear the erythrocytes. Currently CO2 is used as medium for digital subtraction angiography in patients with renal insufficiency and was first used in humans by Hawkins in 1982. The other alternative for angiography, iodinated contrast medium, is nephrotoxic and thus is avoided in these patients for fear of exacerbating the patient's acute or chronic problem. Another group where CO2 angiography is employed is history of a contrast allergy. Although this technique is usually used under these circumstances, Kerns et al reports conducting CO2 angiography in as high as 20% of their patients with abdominal and lower extremity studies. In addition to the benefits of patients with allergies and renal insufficiency, CO2 is extremely safe in a variety of arterial and venous applications. It is 20 times as soluble as room air and is expired through the lungs in a first-pass-type effect. The current contraindication to CO2 digital subtraction angiography is that the cerebral arterial circulation should never be exposed to CO2 because of possible neurotoxicity. Relative contraindications include use in the presence of a large arteriovenous shunt, with nitrous oxide anesthesia, and used cautiously in patients with chronic obstructive pulmonary disease. Dextran has been used in the past in the critical care setting of human as a volume expander with the rare side effects of anaphylaxis and nephrotoxicity. It has also been used in human coronary arteries with iOCT as a blood displacement medium. Finally it has been used with iOCT in a proximal occlusion model. The main complaint in the final study was a burning sensation that lasted < 10s. Iodinated contrast is the current gold standard for infrainguinal angiography imaging in patients without renal insufficiency and has also been used with iOCT to improve image quality in human coronary arteries as well as carotid arteries. The current debate in the literature for iOCT medium is between iodinated contrast and dextran and CO2 may offer a superior method of iOCT imaging during lower extremity occlusive disease interventions.

Official Title
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Optical Imaging Measurement of Intravascular Solution Efficacy Trial

Conditions
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Peripheral Artery Disease

Intervention / Treatment
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* Procedure: Contrast Injection
* Procedure: Dextran Injection
* Procedure: CO2 Injection
* Procedure: Heparinized Normal Saline Injection


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age greater than or equal to 18 years English speaking Scheduled to undergo an infrainguinal angiogram and/or endovascular procedure as determined by a vascular surgery specialist Superficial Femoral Artery diseased segment Exclusion Criteria: Acute or Chronic Renal insufficiency with Cr >1.5 Chronic obstructive pulmonary disease Congestive heart failure (American Heart Association C lass III or IV) Acute limb ischemia, defined by a significant change in symptoms (one category on the Rutherford scale within the previous 14 days) Concurrent oral anticoagulant therapy that cannot be safely withheld

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: iOCT<br>Arterial access will performed by the operating surgeon. An aortic and infrainguinal angiogram using the standard method of intravenous iodinated contrast under digital subtraction fluoroscopy will be conducted in the usual manner according to the vascular surgeon. A 54 mm section of Superficial Femoral Artery will be chosen for study imaging. An intervention sheath or injection catheter will be placed just proximal to the area of interest. An 0.014 wire will be passed distal to the area of interest. The patient will then undergo OCT of this 54mm section with each of the three mediums below using a continuous flushing method through injection catheter. All OCT imaging will be collected at a rate of 25mm/sec. In the event of a subsequent procedure, OCT imaging will again be performed | Procedure: Contrast Injection<br>* Media #1: IV Contrast (Omnipaque 350) will be continuously injected at a rate range of 2.5-6ml/s for a maximum of 5 seconds. (Volume range of 12.5- 30ml) Intervention protocol will be followed per Cross-Reference Intervention.<br>Procedure: Dextran Injection<br>* Media #2: Dextran 40 Solution will be continuously injected at a rate range of 2.5-6ml/s for a maximum of 5 seconds. (Volume range of 12.5- 30ml. Intervention protocol will be followed per Cross-Reference Intervention.<br>Procedure: CO2 Injection<br>* Media #3: Carbon Dioxide (CO2) will be injected with large volume hand injection syringe as per the usual protocol. This be done with particular attention to avoid air in the closed system. In addition to supine, there is also an option that the patient's distal limb may be elevated to improve the flow of CO2 during injection. The surgeon will also wait at least 2 minutes between each CO2 injection to allow any potentially trapped CO2 to dissolve. A range of 20-60 ml will be used with each hand injection based on the data from the initial 5-10 pilot patients. Intervention protocol will be followed per Cross-Reference Intervention.<br>Procedure: Heparinized Normal Saline Injection<br>* Media #4: Heparinized Normal Saline (Heparin NS) will be hand injected using 20 mL (2 U/mL) in antegrade fashion.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Quality of Images | The metric of image quality was the clear imaging field (CIF), which was defined as a cross section in which ≥270° of the vessel wall architecture was visualized. This has been used previously to quantify adequacy of clearance in OCT image comparison. Two independent observers, blinded to the flush medium used, analyzed all OCT frames in each pullback sequence. Any disagreement >10% was resolved with a consensus re-evaluation at a later time point by the same reviewers. Each individual cross section was assigned a designation of quality or insufficient quality; thus, a quality image proportion was generated for each run by taking the mean of each observer's determinations | 1 month | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Superficial Femoral Artery Plaque Composition by Flush Medium |  | 1 month | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Contrast, Optical Coherence Tomography, Dextran, Carbon Dioxide, Imaging, Catheter, Lower Extremity Artery