Breakthroughs in Technology for the Assessment and Treatment of Cardiovascular Disease

Held at the 2005 American College of Cardiology Scientific Sessions in Orlando, a satellite symposium on new imaging and treatment technologies brought together leading names in cardiology to discuss technological breakthroughs in imaging, navigation, and mapping. Panelists discussed their own experiences and the ramifications of these breakthroughs, including the fact that they are changing not just the way we see cardiology, but also the way we will think about it in the future. Albert E. Raizner, MD, FACC, FSCAI, Program Director at the The Methodist DeBakey Heart Center in Houston, Texas, presented his experience with magnetic navigation as a breakthrough technology that can make examinations and diagnostic procedures simpler, easier, and more precise. He noted that the basic problem in navigating the heart is that the coronary arteries are a curving, twisting network of vessels that exist on three planes, wrapped around a conical surface (which happens to be off-axis to any of the three planes). Navigating this network is difficult in the ideal patient, but in patients with small-diameter vessels, tortuous arteries, or multi-vessel disease, it may be impossible. Dr. Raizner also commented that the early manually steerable catheters opened up new territories to the interventional cardiologist, but most physicians in the cath lab have probably felt like they have reached the outer limits of that territory on more than one occasion. Unprecedented access is now available with the Axiom® Artis dFC (Siemens Medical) and Niobe® system (Stereotaxis, Inc.) in a magnetically guided system for navigating the coronary arteries. Two magnets (external to the patient) create a field of specified direction and magnitude, for example, 15 cm at about 5 Gauss. A magnet in the distal tip of the catheter aligns with the magnetic field. The physician adjusts the vectors of the magnetic field to guide the catheter through the vessels. Unlike steerable catheters, which rely on physician dexterity, a magnetic catheter can maneuver at sharp angles and even make 90° turns. The distal tip guides the catheter through the vasculature. This results in less radiation and could work with remote systems, opening the door to its eventual deployment with robotic systems. Current technology does exist which allows a robotic system to identify the center line of a vessel and make adjustments as the vessel changes. It is possible to imagine robotic access to the coronary arteries in the future, where operators could navigate the seemingly inaccessible locations in and around the heart. In a magnetic navigation system, orientation changes about every three seconds and the catheter itself is able to interrogate the vessel as it advances. Dr. Raizner reported median placement time for a catheter of nine minutes and median total procedure time of 64 minutes. Advances in CT imaging and magnetically guided catheters will improve image results for tortuous vessels, internal mammaries, long lesions, and bifurcated vessels. The latter is especially important because the introduction of bifurcated stents is anticipated at some point in the near future. Other applications for magnetic technology might be guiding catheters for procedures involving structural heart disease, percutaneous valve repair/ replacement, or closing patent formen ovales (PFOs). The transition from 2D to 3D imaging is reshaping invasive cardiology, according to Neal S. Kleiman, MD, FACC, FSCAI, Program Director at The Methodist Hospital in Houston, Texas. Technologically, moving from 2D to 3D involves computerized reconstruction, a volumetric-based procedure requiring multiple views integrated into an existing image chain and with some correction along the way. The computer calculates multiple vessel diameters and lengths, even recommending next views, and reconstruction requires less than two minutes. The challenges of 3D imaging are many. Equipment exists but is not widely available. Reconstruction requires advanced expertise and interaction from technicians. Information technology may seem like a more quiet breakthrough, but John Stewart, President and CEO of The Heart Center of Indiana, Indianapolis, Indiana, addressed how computers are continuing to streamline the administrative side of medicine. According to Stewart, this technology will slip into the background as it gets more advanced and allow clinicians to move to the foreground of patient care. Stewart spoke about the concept of an integrated datastream, including electronic records which update automatically as the patient moves through the system. Although time-consuming to transition, electronic records have proven to be cost-effective both within and beyond the hospital walls, as major carriers realize cost benefits in processing electronic versus paper claims. This may even result in faster payment to providers and better service to subscribers. An electronic system can also generate more accurate data on outcomes, average length of stay, pharmacy costs, and any number of other variables. Most traditional hospitals employ a chief financial officer and a business team to make investment decisions, yet they rarely have the right performance data to guide their choices. A thoroughly integrated approach improves the quality of clinical and economic data which, in turn, allows the business side of the hospital to get the information it needs to invest wisely in the future. Although fewer than 40% of American hospitals have cost accounting centers, they can be crucial to the financial well-being of any hospital. A cost accounting center looks at a specific procedure or treatment (or any clinically defined event) and calculates costs. The reliability of cost accounting data depends in part on the homogeneity of the data. When the data all come from the same known and reliable sources, reports are obviously more accurate and valuable for both long- and short-term planning. Thus, integrated data systems not only improve care, they can improve the bottom line. In fact, Stewart commented, you can't really do the first one without the second one following. Norman E. Lepor, MD, of Cedars-Sinai in Los Angeles, California, reported on his own clinical experience with 64-slide cardiac CT and its integration into a cardiology group practice. Lepor stated that noninvasive CT coronary angiography has the potential not only to revolutionize interventional cardiology but also have ramifications beyond cardiology. It is an effective screening tool for coronary artery disease and other forms of heart disease that go far beyond looking at traditional risk factors. (For instance, about 15% of all patients who present with an acute myocardial infarction will have no traditional risk factors for heart attack.) The power of diagnostic CT imaging is not in the image but in how the image can be utilized. Lepor gave several examples: a hemodynamically stable patient with chest pains, a change in the ECG indicative of left-bundle-branch-block, or a cardiac mass in the atrium. CT can also be used prior to ablation or to clarify coronary vein anatomy before implantation of a cardiac resychrnonization therapy (CRT) device. Angiographic computed tomography can now visualize the soft tissue of the heart from an image captured in one 15-second breath-hold. The scan takes seconds, so therapeutic decisions can be made on-the-spot, based on actual data rather than probabilities. In an outpatient practice, CT can effectively triage chest pain patients and allow some patients to avoid the emergency room. CT can also be integrated with other types of cardiac imaging systems, such as echocardiography systems, stress tests, and magnetic resonance (MR) imaging. In fact, CT is often compared to MR, and both offer distinct advantages. MR is the better tool for evaluating myocardial viability, ventricular disease states, and certain valvular diseases. Unlike CT, MR does not use radiation or active contrast medium, and MR can be effectively combined with a stress test. However, for effective use, MR requires a radiologist or, at the very least, a clinician with advanced radiological expertise. When selecting CT scanners, the needs of the practice must be matched against the equipment. Dr. Lepor’s Westside Cardiovascular Medical Group opted for the 64-slice CT scanner rather than the more economical 16-slice unit. When selecting any significant piece of capital equipment, he notes that it is important to check out reimbursement levels since there can be geographical nuances that may affect a local decision. Lepor and his colleagues selected the 64-slice CT SOMATOM Sensation Cardiac 64 system from Siemens. It offers grantry rotation of 0.33 sec and temporal resolution of 83 ms. The technician can freeze an image of the heart, even during a tachycardia. Aasha S. Gopal, MD, FACC, FAHA, Director, Echocardiography, St. Francis Hospital The Heart Center, Roslyn, New York, spoke about clinical applications of 3D echo, which will allow cardiologists to see problems sooner because of greater image accuracy. According to Dr. Gopal, the biggest drawback to echocardiography has always been its lack of spatial registration. The use of improved transducers and locators has improved endocardial differentiation. New devices, such as the Acuson Sequoia ultrasound system, offer patient-specific optimizing technology. The returning echo signal is used to optimize the axial and lateral gain, which is applied to the real-time image as soon as the transducer contacts the patient. This minimizes noise for clearer images. One of the main areas of application for 3D echocardiography involves assessing left-ventricular ejection fraction (LVEF) values. Since several recent and well-publicized clinical studies have demonstrated the role of left-ventricular systolic function in stratifying a patient's risk of sudden cardiac arrest, LVEF tests are in high demand, particularly for heart attack survivors. In conventional echocardiography, data acquisition and rendering were two separate procedures. This required the sonographer to operate the transducer with one hand and a keypad with the other. This new system allows data acquisition and image reconstruction to be performed in one step, on one platform. Dipan J. Shah, MD, Director, Nashville Cardiovascular MRI Institute, Brentwood, Tennessee, spoke about cardiac magnetic resonance imaging (CMR), which he believes is changing not just how we visualize heart disease, but how we think about it as well. While CMR has been extremely valuable in providing data to help interventional cardiologists, it has an amazing ability to answer questions cardiologists did not think to ask. It is in grappling with these unknown unknowns, the things we don’t know that we don't know that CMR will most challenge conventional notions of heart disease and treatment models. For example, it was through CMR that we learned that ventricular wall thinning in certain heart disease states can be reversed. This was not information any clinician was specifically seeking, but it has come to our awareness through CMR technology. In clinical cardiology practice, CMR offers high spatial and temporal resolution and provides the flexibility of multiple slice locations. There are no body area limitations. It has no radiation, no contrast medium (other than inert substances), and no stress test. CMR has been shown to be particularly effective in patients with hypertrophic cardiomyopathy (HOCM) and nonischemic cardiomyopathy. It has also been useful in ischemia testing for myocardial perfusion. Hybrid images (combining two imaging technologies) or multiple images (using two separate techniques independently but viewing results together) provide the big picture of the condition, and information may appear in one imaging technique that is not adequately captured in another. Jack A. Ziffer, MD, PhD, Chief of Radiology, Baptist Hospital of Miami, Miami, Florida, spoke about the role of hybrid imaging in evaluating acute chest pain. When properly done in the appropriate patients, hybrid imaging can save time and money, but there are drawbacks. The general paradigm for imaging cardiac patients is sequential, with branches of a decision tree between steps. For example, one image is taken and assessed. A decision is made, at which point the patient might have a second type of image made, which is then evaluated and another decision made. In other specialties and perhaps one day in cardiology, two distinct image types may be required from the outset, which would be obtained and evaluated simultaneously. As a general rule, hybrid imaging techniques are about one generation behind the technology of the individual components. For early adopters of technology, working with hybrid set-ups may seem like going back in time rather than working with the latest thing. Hybrid systems require more equipment, so there may be cost or acquisition issues. Upgrading becomes challenging, because changing out one part of the system may adversely impact other parts of the system and require more technical support. Hybrid systems are increasingly important, but before any new equipment is introduced, Ziffer suggested that the hospital or clinic must first determine whether this new technology meets or exceeds the sensitivity and specificity of the existing technology. Technology is changing the way physicians practice interventional cardiology. Yet the real revolution will begin when technology slips into the background and allows the true continuum of care that is, patient and caregiver to take its rightful place. Technology in service of interventional cardiology will not only improve care, it will improve both physicians’ and cath lab professionals’ abilities to function more truly as caregivers rather than service providers.

*This event was reported on by Jo Ann LeQuang. Aticle content was not reviewed by members of the faculty.