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Enhancing Vascular Imaging by OCT at the Charité Hospital Based on an interview with PD Dr Bernhard Witzenbichler of the Charité Hospital (Berlin, Germany) Professor Witzenbichler studied medicine in Munich and Düsseldorf, Germany, then completed a 3-year residency in Boston, MA, USA. He joined the Charité Hospital Campus Benjamin Franklin in 1998, performing coronary diagnosis and – from 2001 – interventional procedures. Charité Hospital Campus Benjamin Franklin has four catheterization laboratories staffed by five senior interventionalists and four fellows. Professor Witzenbichler performs approximately 1000 catheterization operations annually, including approximately 600 of the 1600 interventional procedures conducted at the hospital each year, encompassing coronary, renal artery and other interventions. A powerful imaging modality matures Optical coherence tomography (OCT) was first demonstrated in 1991 for imaging the retina. OCT provides cross-sectional images of blood vessel morphology by analyzing the interference patterns of near-infrared light refracted from the tissue. The micrometer-scale resolution of OCT is 10-times higher than that of intravascular ultrasound (IVUS), an established modality used to image blood vessel tissues. Until recently, the application of OCT in coronary catheter procedures was limited by the requirement to occlude the coronary artery for about 60 seconds while imaging took place, causing pain and increasing risk to the patient. The new-generation LightLab C7-XR™ OCT system marks a radical improvement because it “provides very fast pullback; within 3 or 4 seconds you have a pullback length of 55 mm in the coronary artery, without blocking the artery”. During OCT imaging, contrast medium (used in angiography) is injected into the vessel to ‘clear the blood’ and provide an uninterrupted imaging signal. Precise control of contrast flow-rate using the AngioTouch® Hand Controller All quotes are taken from the interview with Professor Bernhard Witzenbichler Bracco Group Interpretation of OCT results during a cardiac catheterization laboratory procedure To achieve consistent blood clearance, the CVi system allows the interventionalist to precisely control contrast injection, using the ergonomic AngioTouch® Hand Controller, at the same time as manipulating angiographic catheters. “Without using the CVi system, I’m convinced that it would not be possible to get the same quality and (even more importantly) I think it wouldn’t be so reproducible”. Clinical applications of OCT Professor Witzenbichler began using OCT as part of a clinical study of treatments for acute myocardial infarction, designed to assess the correct positioning (apposition) of self-expanding and conventional stents. OCT is considered uniquely powerful as a tool: To determine the behavior or apposition of stents during procedures or follow-up, and to image the coverage of the stent struts with neointimal tissue. Specific applications may include follow-up assessment of drug-eluting stents or bio-absorbable stents and assessing apposition during the placement of multiple stents. OCT “enables you to see the tissue coverage on the stents, so in terms of the healing processes you get an idea of what’s going on”. Visualization is “not as good with IVUS because the resolution is not good enough – you see the struts but they look much, much thicker”. With OCT “very often you see a visible thrombus or plaque prolapse... which you wouldn’t see angiographically... and which you probably wouldn’t see using IVUS after stent placement”. Correlating the appearance of these pathologies during surgery or at follow-up with outcomes data may provide guidance for future therapeutic procedures. Visualization of a stent in a coronary artery using the LightLab C7-XR™ OCT system During interventions, precise control of the contrast flow rate is advantageous to ensure that imaging occurs exactly when it is most useful for the interventionalist. In addition, low flow rates Broader applications of the ACIST variable flow-rate contrast delivery system are important to prevent stents from becoming dislodged during The ACIST variable flow-rate contrast delivery system was first tested at the Charité Hospital in 2003, and was quickly adopted in their catheterization laboratories for mainstay procedures such as diagnostic angiography. (damage to the vessel wall), both of which can be caused The system allows real-time monitoring of contrast medium volume used during each imaging procedure. Contrast dosing is limited due to mild nephrotoxicity associated with the contrast agent, and must therefore be limited, especially in certain patient groups such as those with renal impairment. “With the ACIST machine it’s very convenient... at any time you have an overview of how much contrast you used”. Compared with manual or power injection, the system can reduce the volume of contrast agent used during a given procedure by approximately 30%, resulting in significant cost savings.1 both of which are not available with manual injection systems. placement and to avoid rare complications such as ‘deflection’ by an undesirably strong injection of contrast agent. Further safeguards to the patient result from the on-board automatic pressure monitoring system and the detection of air bubbles, In the past, after conducting several procedures per day using conventional manual injection, some interventional cardiologists had been left with pain or soreness in their hands. The ACIST AngioTouch® Hand Controller has resolved the issue of hand stress at the Charité Hospital.“Within the last 10 or 20 years there were a lot of inventions for the benefit of the patient, I think this is one where it’s for the benefit of interventionalists!” The future of OCT OCT and IVUS will likely continue to be used in parallel for different applications. IVUS will be used prior to interventional treatment, to plan procedures and define the position of plaque and healthy tissue, because it provides important information about vessel wall composition. Alternatively, OCT is likely to be utilized during interventional procedures or at follow-up, to assess stent apposition, monitor the healing process and identify pathology that indicates potential risk. As OCT is a new technology, there is no standardized protocol for how to analyze the imaging output. Some cardiologists see this as an opportunity for research and publication. If a large clinical trial (perhaps in >10,000 cases) was able to demonstrate a clinical advantage in terms of patient survival rates; for example, preventing stent thrombosis it would promote interest in OCT technology outside of research hospitals. To learn more about ACIST contrast delivery technologies contact us 1-888-667-6648. www.acist.com © 2010 ACIST Medical Systems. All rights reserved. P/N 610.299.01_US 1. Brosh D, et al. Int J Cardiovasc Intervent 2005;7(4):183–7.