Cath Lab Digest - February 2008 - (Page 16)

16 IN DEVELOPMENT FEBRUARY 2008 Study Demonstrates Method to Reduce Radiation Dose with Cardiac CT A study published in the July 18, 2007 issue of the Journal of the American Medical Association found that lifetime attributable cancer risk associated with cardiac CT scan exposure increases with combined cardiac and aortic scanning, and decreases when, during the scan itself, the dose of radiation is lowered so it is generated only during specific segments of the cardiac cycle or the field of radiation is reduced in size. The study showed that extending the scan to include the top of the aorta increases the lifetime attributable cancer risk by up to 46 percent in men and 28 percent in women, depending on age. The analysis also showed that reducing the amount of radiation generated in a single scan corresponded to lower cancer risk. “Inside the scanner, we can reduce the amount of radiation exposure by reducing the field to radiate only organs we want pictures of or to radiate only a single phase of the cardiac cycle. This technique should probably be employed more commonly than it currently is,” said Dr. Sanjay Rajagopalan, John Wolfe Professor of medicine and radiology at the Ohio State University Medical Center and senior author of the study. For patients whose cancer risks outweigh potential benefits of a diagnostic cardiac CT, Rajagopalan suggests optional tests include a stress echocardiogram, a stress ultrasound or a magnetic resonance imaging test. He also noted that the 64-slice cardiac CT scan generates less radiation than commonly conducted nuclear studies of coronary arteries, such as dual isotope stress tests — a fact he said is generally not acknowledged when discussing cancer risk associated with diagnostic heart exams. “With this new generation of CT machines, there is an assumption of cancer risk, but there is very little information available about what characteristics might influence that risk,” said Dr Rajagopalan. “There has been an explosive increase in the use of this test to look for blockages in arteries because it offers a fast, noninvasive diagnosis. With this widespread usage, we need to help patients make informed choices and also help physicians balance the benefits of determining the correct diagnosis with the risks of future cancer risk.” CT scans have been used to examine coronary arteries since 1998, but the 64-slice technology for cardiac scans has been available only since 2004. Figure 3. From the live case performed at TCT 2007. Angio image illustrating the retrograde approach. The wire is engaged from the left side and advanced through a septal branch to re-enter the distal right coronary artery. right coronary artery (RCA). Then, with the modified workstation, we can take the CT analysis of the entire right coronary artery and overlay it over our fluoroscopy in the GE Innova room. The CT image of the RCA is displayed so that it is transparent over the fluoro. You can also get just an outline of the vessel, superimposed on the fluoroscopic vessel. If you iso-center it, just move the gantry and change your angle, and the CT angle will change also. The technology provides consistent overlay of the entire path of the vessel or any segment you wish. You may only want the occluded part of the vessel. Perhaps you may want what you can see on angio eliminated and only the overlaid CT segment visible. This is possible. You could also just have, for example, the angio-visible proximal vessel eliminated, as well as the entire distal vessel, even out to the part visualized by collaterals. You can visualize these in CT format as well. It gives you a lot of flexibility in guiding your wire, as well as other devices, through the total occlusion. It seems that the CT overlay technology may allow for less use of contrast during fluoroscopy. Yes. We always work with collateral visualization with CTOs. If there aren’t collaterals from the ipsilateral artery, we do a contralateral injection. This technology, by overlaying the entire vessel, may allow us to eliminate that second injection and minimize the dye for CTO patients, because we have the entire vessel already outlined on the fluoroscopy. CT overlay offers the potential of extending this technique, which can be very contrastintense, and minimizing the contrast to a great degree. How much, we don’t know yet. We’ve only done a halfdozen cases so far, but I think that is a big part of its potential. Could you describe the live case you did at TCT? This case was a very complex right coronary artery with an occluded stent virtually all the way to the ostium. Since the stent actually extended somewhat into the aorta, it was even difficult to seat the guide catheter. Needless to say, because of the unusual angulation of the entry of the guide into the stented segment, it was difficult to get wires to penetrate. We used the retrograde technique, using transeptal collaterals from the left anterior descending artery. Advancing the wire retrograde into the stent and then dilating retrograde allowed us to clear a path that would permit us, finally, to enter antegrade with a wire and balloons. We used the You could, for example, take the CTO overlay to any angioplasty you are doing, and just use the overlay to guide the wire, traversing the vessel, and not have to do repeated injections. overlay of the GE CT to guide our path and minimize the need for repeated injections of fluoroscopy. The outcome was superb. Where does the retrograde technique stand in terms of how people are approaching CTOs today? Well, if you go to Japan, it’s very commonly done and I would venture to guess that maybe a third of CTOs in the Japanese major centers are being done this way. In the United States, it is much less frequent. In my mind, it is a very important tool because it will increase your success

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Cath Lab Digest - February 2008 Bay Regional Medical Center ENDEAVOR IV: A Zotarolimus-Eluting Stent Versus a Paclitaxel-Eluting Stent in a Randomized Clinical Trial A 3D CT Vessel “Roadmap” Over Live Fluoroscopy for Chronic Total Occlusions Contents Clinical Editor’s Corner An Evaluation of Cath Lab Turnaround Time Commentary: An Evaluation of Cath Lab Turnaround Time Excerpts from Chapter 19. STEMI Interventions – Future Perspectives The Potential Clinical Utility of Intravascular Ultrasound Guidance in Patients Undergoing Percutaneous Coronary Intervention With Drug-Eluting Stents The Ten-Minute Interview with…Debbie Charlton, RN The Society of Invasive Cardiovascular Professionals (SICP) at Transcatheter Cardiovascular Therapeutics (TCT) 2007 The Cath Lab is a Business: Do You Have the Knowledge to Stay Afloat? Incidence and Predictors of Vascular Complications after Invasive Coronary Procedures: A Prospective Analysis Ask the Clinical Instructor: A Q&A Column for those New to the Cath Lab Volunteer Survey SICP* Section Meetings Calendar What Do You Think? CEU Education Center Clinical & Industry News Classifieds Advertisers Index

Cath Lab Digest - February 2008

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