Cardiac Imaging News

According to a new Canadian study, radiation from widely-used medical tests can increase the risk of developing cancer. Montreal doctors who followed nearly 83,000 patients suffering from heart attack for five years found that exposure to low-dose ionizing radiation from common tests used to diagnose and treat heart problems are associated with an increased risk of cancer. Dr. Louise Pilote, director of the division of internal medicine at the McGill University Health Centre, said: “The risk is small, but it's definitely there and the higher the level of exposure, the higher the risk. These are not benign tests." For every 10 millisieverts of radiation, there was a three percent increase in the risk of developing cancer over the next five years. An angiogram with angioplasty, a procedure to open blocked coronary arteries being the most reliable treatment for heart attacks and angina, exposes patients to about 15 millisieverts of radiation. A mammogram, by contrast, exposes women to radiation doses of less than one millisievert. Although most of participants in the study were exposed to low or moderate radiation doses, a substantial number were exposed to high levels. Younger patients, not older ones, were more likely to be exposed to higher doses of radiation. The authors write in the Canadian Medical Association Journal: "For the average patient surviving an acute myocardial infarction, life expectancy is substantial. Our results suggest that exposure to low-dose ionizing radiation directly affects the likelihood of cancer. Although these patients most likely will die of cardiac-related causes, the increased exposure to low-dose ionizing radiation increases their risk of cancer and perhaps mortality." While an individual person's risk appears small, from a population perspective it could be important, McMaster University researchers noted in a related commentary. "The real trouble arises when an individual undergoes multiple tests or procedures," they said. It's impossible to identify how many of the cancers developed in the study were the direct result of radiation exposure, said Mathew Mercuri, a graduate student at McMaster and a project manager at Hamilton Health Sciences. The McMaster group estimated that there would be one patient developing cancer for every 2,000 patients receiving a 20-millisieverts dose of radiation from medical imaging. Many of the patients in the Quebec study received a dose in that range. The results raise questions about whether it's time to reconsider our enthusiasm for CT scans and other procedures that rely on ionizing radiation. The researchers recommended that the number of radiation-based tests and procedures each patient undergoes should be tracked in order to estimate their cumulative radiation dose. "Nobody is keeping track of the level of radiation that patients are exposed to," Pilote said. However, scientists stressed that the benefit of tests such as CT angiograms and nuclear scans, where patients are injected with radioactive dyes, still exceed its risks. "What I'm concerned about is that patients are going to second-guess their physicians and refuse to have tests they need, and that physicians are going to be angry with us for scaring patients. The vast majority of tests that we're doing are appropriate. But routine imaging of patients who are not having any symptoms on a regular basis is probably something we should not be doing.", said co-author Dr. Mark Eisenberg, a professor of medicine at McGill University and staff cardiologist at Montreal's Jewish General Hospital. The use of CT scans and other tests that use radiation is increasing in Canada and exploding in the United States. One in 10 Canadians surveyed by the Canadian Centre for Policy Alternatives in 2009 said they had paid out-of-pocket (or their employer had) for a CT scan of their lungs, heart or entire body, even though they had no symptoms of a health problem; 61 percent of Canadians surveyed said they would take a free full-body CT over $1,000 cash. Several billion imaging studies are performed annually worldwide; about one-third of them in cardiovascular patients, according to the American Heart Association. The new study involved 82,861 heart attack patients in Quebec; 77 percent underwent at least one test or procedure involving ionizing radiation in the first year after suffering their heart attack. Studies involving atomic-bomb survivors have found that people who lived close to the blast sites had a higher incidence of cancer than those who lived further from the epicenter. “But little is known about the relationship between exposure to low-dose ionizing radiation from medical procedures and the risk of cancer," the researchers write in the Canadian Medical Association Journal. Using Quebec medicare records, the researchers identified patients who had a heart attack between 1996 and 2006. They excluded patients if they had been diagnosed with cancer in the year before or the year after their heart attack. Patients were followed for five years on average. Cardiac catheterization and angioplasty accounted for about 64 percent of the radiation from cardiac procedures. Angioplasty uses a balloon to open narrowed or blocked arteries, and stents, tiny, cage-like tubes or scaffolds, to keep arteries propped open. A total of 12,020 cancers were diagnosed during follow up. "We found a dose-dependent risk associated with the radiation," Eisenberg said. Cancers of the abdomen, pelvis and thorax (including breast cancer) accounted for about two-thirds of the cancers detected. Eighty-four percent of the radiation the patients were exposed to occurred in the first year after their heart attack, and it was almost all related to studies looking at their heart. "We don't want people to worry," Eisenberg said. "What we've shown here is an association, but it's very small."What's more, for heart attack survivors, the likelihood of having a repeat heart attack or dying from a heart condition "is much, much higher than the concern about developing a cancer down the line," he said. Still, there are other tests that can be done that involve lower, or no radiation exposure such as stress tests on treadmills, MRIs and echocardiography. Doctors sometimes order routine tests on patients who have had bypass surgery or angioplasty simply for reassurance, the researchers said. "There are some doctors who are ordering nuclear tests on these patients every couple of years to look for blockages coming back, even if the patient is not experiencing chest pain and otherwise seems healthy. That's the kind of situation I think we should maybe think twice about."  Eisenberg ... Read more

InfraReDx, Inc., a leading developer of intelligent cardiovascular diagnostic imaging technologies, will start commercialization of its LipiScan™ IVUS Coronary Imaging System throughout Europe after receiving the CE Mark approval. With CE Mark approval, the LipiScan IVUS system is the only device available in both U.S. and Europe for the detection of the plaques that complicate stenting and believed to be the leading cause for most heart attacks. Donald Southard, president and chief executive officer of InfraReDx, said: "Receipt of the CE Mark for the LipiScan IVUS system is an important regulatory milestone for InfraReDx as we advance our global commercialization strategy to make this novel product available to physicians worldwide. With the U.S. launch of the system well underway, we are already receiving tremendous interest from physicians in Europe and are in active discussions with prospective distributors of the product. We are currently finalizing our European marketing plan and expect to launch the LipiScan IVUS in select countries in the coming months." The LipiScan IVUS Coronary Imaging system received U.S. Food and Drug Administration (FDA) approval in June 2010. The system includes the world's first and only cardiac catheter to combine intravascular ultrasound (IVUS) and near-infrared (NIR) spectroscopy to help clinicians identify and characterize lipid core coronary plaques. In a single catheter pullback, the LipiScan IVUS provides physicians with a traditional IVUS image that clearly displays important structural parameters of the lesion, including its site, length, and degree of stenosis, in addition to evaluating stent placement. Moreover, the system performs spectroscopic analysis of optical data to produce a Chemogram™ map that determines the location of lipid core plaques and assesses their lipid core burden. Integrating and co-registering the Chemogram with IVUS provides key information to cardiologists during the cardiac catheterization procedure. Patrick W. Serruys, M.D., Ph.D., professor of interventional cardiology at the Thoraxcenter, Erasmus University Hospital, Rotterdam, Netherlands, said: "The LipiScan IVUS system is an important new intravascular imaging tool that will be of immediate value to interventional cardiologists for the diagnosis and management of their patients. This impressive multimodality system provides an IVUS image of the vessel while simultaneously performing spectroscopic analysis for the accurate and immediate detection of lipid core plaques demonstrated to complicate stenting and suspected to cause most heart attacks. The Thoraxcenter is proud of its association with InfraReDx and the role we have played in the development of the LipiScan IVUS system and imaging ... Read more

VisualSonics Inc., a leader in real time, in vivo, high-resolution micro-imaging systems and a wholly-owned subsidiary of SonoSite Inc., announced that its new VevoStrain™ software technology has been featured on the cover of the April issue of Circulation Research, Journal of the American Heart Association. VevoStrain provides advanced imaging and quantification capabilities to study sensitive movements in the heart muscles particularly the myocardium. The VevoStrain technology enhances high-resolution imaging capabilities of high-frequency ultrasound with highly sensitive measurements of subtle variations in the myocardium. The VevoStrain software allows visualization of wall motions in the heart, including the entire heart as well as defined regions within the heart. Measurement capabilities include quantification of displacement, velocity, strain and strain rate. Researchers at Brigham and Women's Hospital, Harvard Medical School demonstrated the utility of VevoStrain technology as a non invasive, highly sensitive and rapid cardiac phenotyping tool in their seminal paper on in vivo strain analysis.   Ronglih Liao, MD, Associate Professor of Medicine, Harvard Medical School said, "We believe that with strain analysis, we now have a very effective and efficient method for non-invasively detecting early cardiac performance irregularities in mice. While recognizing that this method requires special expertise and experience to implement, we are very excited about prospects for applying these analyses in future studies of experimental therapeutics." The VevoStrain software replaces Tissue Doppler imaging as the assessment tool for quantifying myocardial mechanical function and deformation. Additional features of the software include measurement of cardiac wall motion abnormalities, dyssynchrony (delayed ventricular activation and contraction) and myocardial ... Read more

Toshiba Medical systems has announced that it is currently working to integrate 3D Wall Motion Tracking and Tissue Enhancement technologies in its Aplio Artida cardiac ultrasound system. Moreover, Aplio MX, Aplio XG and Xario XG ultrasounds are available with the Auto IMT feature for measuring intima-media thickness of the carotid artery. 3D Wall Motion Tracking offers a new era of dyssynchrony imaging and advanced regional wall motion assessment. It helps electrophysiologists in optimizing pacemaker placement and function. It also demonstrates 3D ejection fraction, volumes and regional and global strain function. The Toshiba-exclusive software; Tissue Enhancement, has the ability to improve image uniformity and endocardial border delineation, especially in difficult-to-scan patients. Another feature available on Toshiba’s shared service ultrasound systems, Aplio™ MX, Aplio™ XG and Xario™ XG, is the new Auto IMT feature that calculates the intima-media thickness of the carotid artery, helping physicians determine a patient’s risk for cardiovascular disease. Toshiba’s Auto IMT can determine the thickness of the near and far arterial walls from three segments of the carotid artery: at an optimal angle of incidence and two complementary planes. Auto IMT uses the collected images following the American Society of Echocardiography (ASE) consensus statement for diagnosis of cardiac risk in people having no ... Read more

Placing pacemaker leads in the optimal area of the left ventricle using computer-enhanced echocardiography imaging produced a 50 percent lower combined rate of all-cause death and hospitalizations compared to patients with conventional lead placement, say researchers. In the first randomized clinical trial to report on the use of echocardiography for placement of pacemaker leads, Dr. Fakhar Kahn, clinical research fellow at Cambridge University, UK, reported the better overall results for patients with heart failure at this week’s American College of Cardiology’s 60th Annual Scientific Session (ACC.11). “Optimal placement of pacemaker leads is determined by the location of cardiac scar tissue and areas of delayed heart muscle contraction, which vary considerably among patients,” said Khan in a prepared statement. “Our improved results with an individualized approach should change the way pacemaker leads are implanted in this population of patients.” In the study, researchers randomly assigned 220 patients with left bundle branch block who were scheduled for cardiac resynchronization therapy (CRT) to either standard pacemaker implantation or a new procedure called, speckle tracking echocardiography (STE). Patients averaged 71 years old and ranged from 63 to 78. Speckle tracking echocardiography (STE) is a non-invasive method for evaluating left ventricular global and regional function. It is named for the speckles that appear in grey scale two-dimensional echographic images caused by the scattering, reflection and interference of the ultrasound beam in myocardial tissue. The speckles form “fingerprints” randomly distributed throughout the myocardium that represent tissue markers that can be tracked from frame to frame throughout the cardiac cycle by computer. In this study, researchers use STE to identify the latest area of contraction in the heart cycle, which has been associated with better response to CRT. In the STE group, physicians implanted the wire leads to cardiac resynchronization pacemakers guided by speckle tracking echocardiography information to position the left ventricular lead within the site of latest contraction. In the control group, physicians implanted the CRT device using standard procedures without reference to the STE data. All patients had the lead positions defined by biplane fluoroscopy. Patients were then classified into three groups, those with the lead implanted within the site of latest contraction, next to the site of latest contraction, or remote, defined as more than two segments away from the latest site of contraction. This analysis showed that a 61 percent of patients in the STE group had lead placement at the optimal site compared to 47 percent of the control group. The echocardiography group had better overall results than the control group on all clinical endpoints, including a 70 percent improvement in the rate of response by reverse remodeling of the left ventricle, compared to 55 percent for the control group. Rate of response by reverse remodeling is a measure of improvement in heart function. The echo group also showed an average improvement on a standard scale for heart failure of 83 percent vs. 65 percent. While there were no differences in the baseline characteristics between the two groups in terms of cardiac output, with an average of 4.77 liters per minute in the echocardiography group compared to an average of 4.67 liters per minute in the control group. After implantation, however, the average cardiac output for the echo group was 6.06 liters per minute compared to an average of 5.57 liters per minute in the control group. Significantly, the results also showed that the closer the lead was placed to the optimal site, regardless of group, correlated with better outcomes. Only 8 percent of patients in either group whose left ventricular leads were place exactly within the target site died from any cause or were hospitalized compared to a 16 percent combined rate of death from any cause or hospitalization due to heart failure in patients whose ventricular leads were placed adjacent to the optimal site. Kahn noted that the software needed to convert standard echocardiography to speckles tracking echocardiography is easily installed by clinics using the conventional equipment. “STE software can be applied to any existing echocardiographic image at no additional risk to the patient,” Khan said. “It makes targeting of the lead feasible at any facility that’s already performing echocardiography and has the software in their system to analyze the images. That makes it widely accessible, even for small centers and non-university hospitals, where more and more pacemakers are being implanted.” By Michael O’Leary, contributing writer, Health Imaging ... Read more

An echocardiographic and fluoroscopic-guided catheter-based procedure is equal to conventional open-heart surgery, a new study shows, at least in terms of survival for replacement of aortic heart valves in elderly high-risk patients. This is the first report from The PARTNER Trial, co-led by Dr. Craig R. Smith, chief of the Division of Cardiothoracic Surgery, New York-Presbyterian Hospital/Columbia University Medical Center, who presented the findings at the American College of Cardiology’s American College of Cardiology’s 60th Annual Scientific Session. ACC.11. The PARTNER trial is designed for patients with severe calcific aortic stenosis who might not be optimal candidates for conventional open-chest valve replacement due to the risks of surgery. “These results clearly show that TAVR is an excellent alternative to surgical AVR (aortic valve replacement) in high-risk patients,” Smith said in a prepared statement. “Recommendations to individual patients will need to weigh the appeal of avoiding open-heart surgery, with its known risks, against less invasive TAVR with different and less well understood risks, as well as the absence of long term follow-up. Future trials will help delineate the role of TAVR in intermediate risk patients.” In both procedures an artificial valve is placed in the aortic valve between the left ventricle and the aorta, the main artery supplying the body with oxygenated blood. With transcatheter aortic valve replacement, or TAVR, a catheter is threaded through the femoral artery to the aortic valve using echocardiographic and fluoroscopic imaging. The collapsed valve is then pushed through the catheter and placed within the natural valve and expanded with a balloon to open the collapsed valve. A wire mesh stent on the outside of the artificial valve locks the implanted valve into place. The large study involved 699 high-risk older patients averaging 84.1 years with severe stenosis of the aortic valve, defined as an opening of less than 0.8 centimeters squared. Patients were randomly assigned to surgery or TAVR at 26 clinical trial sites nationwide. A total of 350 patients underwent open surgery and 349 underwent TAVR. Early study results showed that 6.5 percent of patients in the conventional surgery group died from all causes within the first 30 days after the surgery compared to 3.4 percent of the TAVR group. All-cause mortality at 1 year was similar for the two groups, at 26.4 percent for the surgery group and 22.2 percent for the transfemoral TAVR subgroup. The rate of major strokes among patients in the surgery group, however, was about half that of the rate in the TAVR group. A total of 2.1 percent of the surgery patients suffered strokes compared to 3.8 percent of the TAVR group. Similarly, the rate of major vascular complications within the first 30 days was much lower in the surgery group at 3.2 percent, compared to 11.0 percent of the TAVR. Para-valvular regurgitation, or leaks around the replacement valve also occurred more often with TAVR. Patients in the surgery group had more bleeding complications with rates at 19.5 percent compared to 9.3 percent of the TAVR group. Smith acknowledged the higher rates of stroke and complications in the TAVR group, but noted that the stroke rate had declined 20 percent to 30 percent in this study compared to a previous study. He expects those rates to continue to decline with improved devices and greater experience in performing the procedure. The transcatheter aortic valve replacement procedure has been performed in Europe since 1997, where more than 5,000 people have been treated. Edwards LifeSciences, which makes the collapsible replacement valve, funded the PARTNER study. Dr. Smith has no financial relationship with the company. A second trial, PARTNER II was approved in February to test a new generation valve and delivery system against the current valve and delivery system used in this PARTNER trial. By Michael O’Leary, contributing writer Health Imaging ... Read more

MetroSouth Medical Center, a leading cardiac care center in Chicago, has recently started to use MRI-compatible pacemakers in a number of its patients. Until now, patients with pacemakers weren’t allowed to have MRIs because the magnetic field produces heat, causing the pacemakers to malfunction or induce arrhythmia.  The new Medtronic Revo MRI pacemaker is made out of nonmagnetic metal and has extra insulation on the leads – the wires that attach to the heart—that better absorbs the heat. The first patient to receive the MRI compatible pacemaker in Chicago's southland is a 74-years patient from Illinois Mr. Lee Ryan. He has coronary artery disease and bradycardia (slower heart rate) reaching 35 beats per minute, while normal individuals have about 60-80 heart beats per minute. Sean Tierney, M.D., cardiologist and electrophysiologist at MetroSouth Medical Center, was the doctor implementing the MRI-compatible pacemaker for Mr. Lee. He encouraged his patient to use it. Dr. Tierney said "Mr. Ryan has a history of health problems that will require him to have future MRIs. This new pacemaker is perfect for patients over 65, who are twice as likely to need an MRI as compared to a younger population." Statistics show that there are nearly one and half million patients in the US using pacemakers. Around 200, 00 of them usually need to undergo MRI scans. Yet, they skip the scanning and choose other more invasive procedures as their pacemakers are not compatible with MRI. "Before I got the pacemaker, I was dizzy and fatigued. The usual chores, like splitting wood, were exhausting to me. But after getting this new pacemaker, I no longer have shortness of breath and my energy level has improved greatly," said Mr. ... Read more

Low-dose coronary CT angiography matched the sensitivity of catheter-based angiography, and is a potentially valid alternative to the gold-standard for triaging symptomatic patients suspected of coronary artery disease (CAD), researchers say. Led by Dr. Moritz Wyler von Ballmoos, of the Department of Cardiac Surgery, Children’s Hospital Boston and Harvard Medical School, the researchers performed a meta-analysis of evidence from 16 studies compared a newer technique for CT angiography with that of catheter angiography. Their study appears in the March 15 issue of the Annals of Internal Medicine. “Our systematic review and meta-analysis of currently available data indicate that coronary CT angiography with prospective ECG gating has a high specificity,” the researchers wrote, “and an excellent sensitivity for the detection of morphologically significant CAD, compared with catheter angiography. This CT technique is associated with a low effective radiation dose of 2.7 mSv (millisievert)." The low-dose technique using prospective ECG gating, also known as step-and-shoot or sequential mode, involves applying radiation only at a predefined point in the cardiac cycle rather than over the entire cycle. It has been shown to reduce the radiation dose by up to 80 percent; however, many have questioned whether the limited available reconstruction phases of prospective ECG gating would significantly reduce the amount of information needed to accurately diagnose all of the CAD that may be present. This study found that the technique did not result in any significant loss of information needed for accurate clinical diagnosis, in addition von Ballmoos’ team found this to be true regardless of type scanner used, or radiologists using it. “The diagnostic performance on the patient level is highly consistent across the different CT scanners, centers, radiologists, and study populations that were included in our study,” von Ballmoos told The Hub in an e-mail interview. “This is a very important finding for it suggests that the excellent performance of CT angiography is not tied to one particular type of scanner, protocol, study population or radiologist, but is generally true.” For the meta-analysis, the researchers considered 1,360 studies involving CT angiography, but winnowed that down to 16 studies that met all their inclusion criteria. Seven of the studies used a single-source 64-slice CT, four studies used dual-source 64-slice scanners, 2 were conducted with 320-slice CT, 1 used dual-source128-slice CT, 1 used a single-source 128-slice scanner, and one study used a single-source 256 CT scanner. Overall, 2,622 coronary arteries and 11,518 coronary arterial segments were examined in the 960 patients included in the 16 studies. The mean prevalence of CAD for study patients was 60.1 percent, the mean BMI was 26.5 kg/m2, and the mean age was 63.4 years. All studies included only patients with sinus rhythm. The patient-level pooled sensitivity across all studies was 1.00 (CI, 0.98 to 1.00) and the pooled specificity was 0.89 (CI, 0.85 to 0.92) for low-dose coronary CT angiography compared with catheter angiography. The researchers found greater variation between studies in diagnostic performance at the vessel and segment levels than at the patient level. They thought this might have been due to random variation between studies or variation of study characteristics. When they re-analyzed the data accounting for variations in study characteristics, they found that body mass index and CAD prevalence were independently and significantly associated with the diagnostic performance of low-dose coronary CT angiography in both the vessel- and segment-level analyses. “On the vessel level there was somewhat more variation than would be expected to occur by chance alone,” von Ballmoos said. “In our results and the discussion we offer possible explanations for the difference found between studies and the identified variables should be taken into consideration by radiologists and other clinicians that opt to use CT angiography for diagnosis of CAD.” The researchers noted that the prospective ECG gating CT technique is associated with a low effective radiation dose of 2.7 mSv. This compares with radiation doses of about 12 mSv with retrospective ECG gating, the low-dose technique offers substantially reduced radiation exposure for patients. The researchers concluded that at this low radiation dose the technique may be a suitable imaging test for ruling out CAD in patients with a low to intermediate pretest probability of CAD. However, they caution that their study is based on a small number of studies, many of which were done at a single site. Further studies are therefore needed before widespread diffusion of the technology can be recommended. By: Michael O'Leary, contributing editor Health Imaging ... Read more

DR Systems, a leading developer of healthcare information systems, announced that it will showcase the Unity™ Cardiovascular Information System (CVIS) next month at the 60th annual meeting of the American College of Cardiology. Unity CVIS provides a cost effective, comprehensive cardiology solution for organizations that need a new cardiology system whether to replace old systems, limited systems or to move from tape to a digital solution. Unity CVIS is based on open-standards and technology. This enables cardiologists to integrate patient information and images from multiple departments and data sources into one common platform and database. Utilizing open standards and technology, Unity CVIS is based on a 2010 number 1 ranked KLAS® product category solution. John Conklin, Cardiology Program Director for DR Systems, said: “This year’s theme for the [ACC] show; translating science into patient-centered care with cutting edge education is very synergistic with our vision and goals. Facilitating clinical success through our patient centric Unity platform solutions such as Unity CVIS, we use information technology to interpret scientific data.” Benefits of Unity CVIS include: • Ability to add a wide range of vendor devices or solutions: with its open architecture and integration capabilities, Unity CVIS assist healthcare facilities to adapt to evolving healthcare and technology needs as they see fit. • Comprehensive, longitudinal views of patient data: Unity CVIS integrates images and patient information from disparate sources, meaning cardiologists can view all relevant imaging and non-imaging patient data on a single platform. • Information to improve productivity and overall management: Unity CVIS offers a Management Reports module to help facilities collect data, generate productivity and usage reports, and perform workflow and department analysis. Other features of Unity CVIS include: • Multi-modality support for Cardiac and Vascular Ultrasound, X-Ray Angiography, Coronary CT & MR Angiography, Nuclear Cardiology, and Electrocardiography (EKG) • Advanced imaging manipulation • Integrated clinical reporting • Point-of-care access to patients’ demographic, history, physical, admission, order, and results data. Conklin said: “Our emphasis on consolidation and integration means improved user data-access, improved patient care and safety, and departmental efficiency. It also means a system designed for the kind of workflow and dataflow that cardiologists want and expect.” Live demonstrations of Unity CVIS can be seen at the DR Systems booth during the annual ACC scientific session and expo, April 3-5 at the Ernest N. Morial Convention Center in New Orleans, LA. The DR Systems booth is #2227, in Hall ... Read more

Ziehm Imaging has launched a new generation of the Ziehm Vision RFD mobile C-arm and will be showcasing it at ECR, Vienna, 4-7 March, 2011. Thanks to its lliquid cooling system, the new version can be used over an almost unlimited period of time. ... Read more

Non-radioactive elastin-specific MRI dye offers advantages over x-ray and CT angiography as well as intravascular ultrasound. A new, non-invasive magnetic resonance imaging (MRI) technique can quantify coronary artery disease in patients before they have symptoms, researchers say. Led by Dr. Rene Botnar, chair of cardiovascular imaging at Kings College, London, the researchers used a contrast dye specific for the protein elastin and injected it into mice with atherosclerosis. In experiments conducted by Dr. Marcus Makowski, the researchers were able to produce images with high spatial resolution allowing an accurate assessment of the quantity of plaque buildup on artery walls. The technique has advantages over current invasive methods of coronary ultrasound and CT angiography, Botnar told The Hub in an e-mail interview. Their study appeared online Feb. 20, ahead of publication in the March Nature Medicine. “This approach has the advantage of potentially imaging coronary plaque burden, which only can be done with intravascular ultrasound,” Botnar said, “which is invasive and thus associated with a certain risk for the patient. Alternatively, multi slice CT allows imaging coronary calcification but calcified plaques are usually old and more stable plaques. In addition, calcification affects the lumen scan and does not allow the diagnosis of those segments as a stenosis may be hidden behind the calcium signal.” In the two-year study funded by the British Heart Foundation, Makowski investigated the build up of plaque in mice arteries. The imaging works by using a non-invasive, radiation-free contrast agent called ESMA for elastin-specific magnetic resonance contrast agent. Developed in partnership with Lantheus Medical Imaging, ESMA binds to elastin, which is a key component of connective tissues, and plays a specific role in arteries permitting wave transmission to help blood flow with each heartbeat. It is particularly abundant in large elastic blood vessels. Changes in elastin content and the high abundance of elastin during plaque development, in combination with the imaging properties of ESMA, allow the researchers to not only identify where plaque buildup occurs in the arteries, but to measure the buildup. If successful in developing ESMA for human use it would provide a non-invasive alternative to current methods of assessing coronary artery disease. The gold standard is x-ray angiogram, which involves threading a catheter through blood vessels and injecting contrast dye for imaging with x-rays. The drawbacks include exposure to radiation, reactions to the dye, and the small risk of puncturing a vessel. One limitation is that it cannot show the walls of the arteries. While intravascular ultrasound images do show the artery walls and can reveal cholesterol and fat deposits, like x-ray angiogram, however, it involves threading a catheter through blood vessels. CT angiography, like x-ray angiogram, also poses a slight risk of cancer due to radiation exposure. Current MR angiography is noninvasive and effective for producing detailed images of blood vessels, but MR angiography is not able to see and capture images of calcium deposits. In addition, the clarity of MR angiography images of some arteries does not match those obtained with conventional catheter-based angiography. While Botnar’s approach is at least two years away from human trials, the ESMA contrast MRI overcomes the limitations of current MRI techniques and has the added advantage of plaque characterization by quantifying intraplaque elastin content using signal intensity measurements. “The doctor could image his or her (patient’s) coronary arteries, (measuring) both the lumen and plaque burden as well as adjacent large vessels such as the aorta and potentially the carotid arteries,” Botnar says. “Due to the properties of the contrast agent, it would also allow simultaneous visualization of myocardial infarction and thus not interfere with the conventional cardiac MRI examination of a patient.” By: Michael O'Leary, contributing editor Health Imaging ... Read more

Coronary artery calcium (CAC) scoring may no longer be needed for predicting major adverse cardiac events (MACEs) when a 64-section CT angiography is performed, researchers say. Led by Dr. Hyuk-Jae Chang, of the Division of Cardiology Yonsei University College of Medicine in Seoul, the researchers evaluated the prognostic value of CT angiography alone and with coronary artery calcium scoring for predicting major adverse cardiac events (MACEs) including cardiac death or non-fatal myocardial infarction in patients with low risk of coronary artery disease (CAD). The study was published Jan. 28 online ahead of print publication in the journal Radiology. “Coronary CT angiography is better than CAC scoring in predicting MACEs in low-risk patients suspected of having CAD,” the researchers wrote. “Furthermore, the current standard multisection CT protocol (coronary CT angiography combined with CAC scoring) has no incremental prognostic value compared with coronary CT angiography alone.” The amount of calcium inside the walls of coronary arteries is a good predictor of future cardiovascular events. The score is derived as a compilation of the size and brightness of all the calcium deposits seen within coronary arteries. A normal CAC score is 0, meaning no calcium is seen, and ranges to over 400. Scores over 80 are associated with an increased likelihood of coronary disease, regardless of classic risk factors. Current guidelines state that the CAC test is of limited value in people at low risk of CAD events; however, for individuals at intermediate CAD risk, coronary calcium scoring is considered to provide incremental risk prediction that can help guide therapy. Currently, performing both CAC scoring and coronary CT angiography in combination is the conventional protocol for diagnostic evaluation of CAD. This study adds to the evidence that CAC may be of little value in predicting outcomes for these patients. Given recent concerns about radiation exposure associated with cardiovascular imaging, eliminating CAC would help reduce radiation exposure. The reported study involved 4,338 patients at a single institution who underwent 64-section CT for evaluation of suspected CAD, using both CAC scoring and CT angiography. The tests were performed concurrently using standard scanning protocols. Patients were over 30 years old and the average age was 60. None had prior documented CAD. A total of 359 patients who had elective revascularization within 60 days of the CT scan were excluded from the analysis. Patients were followed for more than two years using phone interviews recording major adverse cardiac events, including cardiac deaths or non-fatal myocardial infarctions. The data was analyzed using multivariable Cox proportional hazards models to predict MACEs. Risk-adjusted models incorporated traditional risk factors for CAC scoring and coronary CT angiography. CAC data and coronary CT angiograms were evaluated by using a Wizard workstation by Siemens Medical Solutions. The researchers divided CAC scores into five groups, those with a score of 0, 1-10, 11-100, 101-400 and over 400. CT scan results were categorized into one, two and three-vessel disease, defined as greater than 50 percent stenosis. During the average follow-up of 828 days (27.6 months), there were 105 major adverse coronary events, for a 3 percent event rate. The presence of obstructive CAD at coronary CT angiography was independently predictive of MACE, and the prognostic value increased according to the number of vessels with stenosis. Using a receiver operating characteristic curve (ROC) analysis, the researchers found coronary CT angiography was superior to CAC scoring as shown by a significantly greater area under the ROC curve (AUC) (0.892 vs 0.810, P < .001).  By contrast, no significant incremental value for the addition of CAC scoring to coronary CT angiography was found. (AUC = 0.892 for coronary CT angiography alone vs 0.902 with addition of CAC scoring, P = .198). “In the multisection CT era, coronary CT angiography is better than coronary artery calcium scoring in predicting major adverse coronary events in low-risk patients suspected of having coronary artery disease,” the researchers conclude. “Furthermore, the current standard multisection CT protocol (coronary CT angiography combined with CAC scoring) has no incremental prognostic value over coronary CT angiography alone in such individuals. Therefore, in terms of prognosis, coronary artery calcium scoring may no longer need to be incorporated into the cardiac CT protocol in this population, considering the radiation exposure.” By: Michael O'Leary, contributing editor Health Imaging ... Read more