Do you know what keeps me up at night? Beyond the sad state of Cleveland sports, I fear that over time, echocardiography may be reduced to a commodity procedure, something akin to the electrocardiogram. We are already seeing the start of this with the gradual chipping away at echo reimbursement and the growth of “advanced” imaging, like CT and MRI. Those of us who live and breathe echocardiography know that this isn’t so: echocardiography is the single most useful test for assessing the structure and function of the cardiovascular system, combining high spatial and temporal resolution in a portable, low-cost, and completely safe procedure. But there is no question that the past few years have seen some buzz connected to CT and MRI, with many of our graduating fellows wanting to focus their clinical and academic energy on modalities other than echo. How can we fight the perception of echocardiography as “basic” imaging? One important way is by continually renewing ourselves and embracing new technological advances as they come along. This doesn’t mean simply leaping on the latest shiny echo toy, but adopting time-tested and clinically-validated advances that can truly help us to manage our patients. I’d like to highlight three areas that we as echocardiographers should be integrating into our daily clinical practice: (1) contrast for left ventricular opacification; (2) three-dimensional (3D) echocardiography; and (3) strain imaging.
First, let’s talk about contrast. There have been ups and downs in the 25 year history of microbubbles for cardiac ultrasound. Remember the halcyon days of the late 90s, when myocardial perfusion echocardiography was going to render nuclear cardiology obsolete? The predicted two billion dollar market by 2000? Let’s just say, not so much. I have a running bet with Sanjiv Kaul, started in 1999, on whether myocardial perfusion echocardiography would out-number nuclear scans at the Cleveland Clinic. Every five years we agree to go double or nothing on the next five years, and I anticipate in a few more cycles I will finally collect from him and be able to retire! But a funny thing has happened in the contrast world. We now have two excellent agents approved by the FDA for better endocardial definition, the value of which has been shown repeatedly with regard to quantifying global and regional cardiac function, identifying thrombi and other masses within the heart, rapidly diagnosing ventricular pseudoaneurysms, and helping to augment Doppler signals. And the safety alarms from several years ago have been largely silenced based on several large studies and the FDA’s softened warning. There is no question that having a liberal policy for using contrast for left ventricular opacification in resting and stress echocardiograms will greatly reduce the number of nondiagnostic studies and will save money over the long run by eliminating the need for other imaging tests. Contrast reimbursement is also one of our shining advocacy victories of the past year, with a $58 increase in reimbursement for contrast-enhanced echocardiography in the hospital outpatient setting. This means there is now a $164 increment when a transthoracic echo is augmented with contrast, more than enough to pay for the contrast and the costs of administering it. And myocardial perfusion? My bet with Sanjiv notwithstanding, this really does work, and someday may be a routine clinical procedure.
The second key technology we need to embrace is 3D echocardiography. 3D echo has been such a long time coming that a few years ago ASE (and ACC) Past-President Tony Demaria remarked, “A child can be promising for just so long.” However, I do believe that at long last this child is finally achieving great things. There are two broad areas that 3D echo has impacted in daily echocardiographic practice. First, it has been proven again and again that cardiac volumes measured by 3D imaging are much more accurate than those based on two-dimensional (2D) echo with its geometric assumptions. When is this important? Consider a patient after myocardial infarction, where an ejection fraction less than 35% indicates the need for an implantable cardiac defibrillator. The second broad application of 3D echo is in the assessment of valvular heart disease, where non-planar structures cannot be fully defined by 2D imaging. Three-dimensional echocardiography, especially transesophageal, provides an unparallel view of valve function, allowing the operator to determine exactly which scallop of a mitral valve is prolapsing, and to measure precisely the size of the aortic annulus to guide transcutaneous aortic valve replacement.
Three-dimensional echo is also the ideal way to guide complex interventions in the cath lab. When an interventionalist tries to pass a wire through a paravalvular leak, fluoroscopic imaging is almost worthless, but 3D can show the wire and the defect precisely, allowing the operator to guide the wire more accurately and intuitively. Three-dimensional echo has always been on the technological cutting edge, from the early days of sequential acquisition of 2D planes with off-line reconstruction, to the current real-time volumetric imaging with massively parallel processing of multiple ultrasound beams simultaneously. With continued improvement in computer power and intelligent image processing, it is now possible to obtain accurate volumes of the heart in just a few seconds and to instantly see complex 3D structures in a variety of projections. In order to integrate 3D imaging into busy clinical laboratories, it is important for both sonographers and physicians to educate themselves, either at live programs or on-line, where techniques for manipulating 3D data sets are taught. Once 3D echo is integrated into a laboratory, it can be done without significant increase in the duration of a study, and the improved diagnostic accuracy will greatly aid patient care.
The final technology that we need to embrace is advanced mechanical imaging with strain and strain rate imaging. Again, this is a tool that has previously been relegated largely to research studies, but the time has come to bring it into daily clinical practice. Studies in the last few years have shown that strain imaging can localize myocardial infarctions, provide evidence for myocardial viability, and detect subclinical left ventricular dysfunction in valvular heart disease. One of the most important applications is in the cardio-oncology realm, where a small reduction in absolute global longitudinal strain can predict future left ventricular dysfunction in patients undergoing cancer chemotherapy. While this approach is still evolving, at the Cleveland Clinic we now study all patients undergoing cardiotoxic chemotherapy with regular strain imaging and 3D quantitative echoes, augmented by contrast, with which we can detect early reduction in ventricular function and react before this is irreversible.
So there you have it: three tools that are right in our hands and ready to impress the clinical world as well as those who pay for it. By embracing new technology and doing our very best to apply it to complex clinical problems, we can assure the viability of echocardiography for years to come.