Echocardiography has been the most widely-used diagnostic test for heart disease for more than 50 years for good reason. It’s portable, safe and technological advancements keep the modality at the forefront of screening and diagnosing heart disease. Looking ahead, cardiologists are eyeing 4D cardiac imaging and ever-smaller equipment.
Several studies presented at the annual meeting of the American Society of Echocardiography (ASE) in June reinforced the understanding of ultrasound as an important tool in combating various forms of heart disease.
A study conducted at the University of Nebraska Medical Center found that real-time perfusion echocardiography is helpful in identifying diabetics without symptoms who are at risk for coronary artery disease. Another study showed that stress echocardiography is a more accurate method for identifying women at highest risk for coronary artery disease (CAD) than traditional stress testing and clinical risk factors.
In September, the Journal of the American Society of Echocardiography released new recommendations to further support the role of stress echocardiography in accurately identifying coronary artery disease and in determining prognosis of patients with known or suspected coronary artery disease.
Regular echocardiography in the resting state is equally beneficial to men and women, but this kind of echo stress testing is particularly beneficial to women. Since the heart lies below the left breast, other types of stress tests, especially nuclear, can be difficult to interpret because breast tissue is in the way, says Vera Rigolin, MD, a cardiologist at Northwestern Memorial Hospital in Chicago. The facility uses Vivid echocardiography systems from GE Healthcare. Plus, radiation used to image the heart also exposes breast tissue. Since echo doesn’t use radiation, there is no exposure risk.
That safety translates well to patients with severe valve issues who require an echo at least once a year to track their condition.
Benefits of real-time imaging
Aside from the benefits of portability and no radiation, echocardiography offers real-time imaging. “With all other modalities, you acquire images and look at them later,” says Rigolin. During echocardiography, sonographers are actually seeing and controlling the images they acquire. If they see an abnormality, they can change focus and really hone in, she says. That’s not possible with other modalities.
Echocardiography has been around for a long time, but continues to make incredible advances in imaging, Rigolin says. It provides “an incredible amount of useful and important information about the structure of the heart.” 2D images give clinicians an idea of how the heart is squeezing, how valves are opening, and whether there are clots, fluid or masses on valves. Doppler imaging gives information about the direction of blood flow, whether there are leaky valves or valves not opening properly, and abnormal blood flow.
3D echocardiography does 2D imaging one better. While 2D echo images one slice of the heart at a time, 3D echo images the entire heart all at the same time. “That gives us a much more realistic and accurate assessment,” she says.
Tissue Doppler is another essential technique that utilizes Doppler to look at the heart muscle rather than the heart chambers and valves. “That gives us an idea of how well the muscle is contracting and relaxing and the timing with respect to how well one wall is contracting in respect to another wall,” Rigolin says. This becomes very important in heart failure patients, with tissue Doppler key in evaluating those patients for certain types of pacemaker devices.
Paula Carr, technical director of the echo lab at the Iowa Heart Center, also appreciates tissue Doppler. “Most of our studies are scanned in harmonic frequency. We hardly ever use fundamental frequency anymore.” Tissue strain imaging (TSI) is used in parts of research. TSI permits a dynamic observation of walls in the lower extremity arteries. With TSI, it is possible to detect a significant reduction in the strain value in lower extremity arteries at risk of developing arteriosclerosis.
TEE avoids interference
Rigolin also cites advances in transesophageal echocardiography (TEE) making a difference in patient care. The patient swallows an ultrasound transducer that is positioned next to the esophagus, which sits directly behind the heart. With this technique, “we get very nice images of the heart structures, particularly those that are situated in the back.” And, there’s no interference from lung and breast tissue or ribs. “Right now, we use TEE very frequently to evaluate certain types of heart pathology. We also use TEE in the operating room to look at patients having valve surgery.” In the future, Rigolin says 3D imaging with a TEE probe is going to be extremely useful.
The 10 Iowa Heart Center locations around the state all use echocardiography systems from Toshiba America Medical Systems, including a mix of Aplio and Xario units. “We try to stay on the cutting edge of technology.” The organization purchased an Aplio XG earlier this year and upgraded recently specifically for the enhancements made to the vascular package.
During her 20 years of practice, Carr has seen tremendous improvements in echo, including color and Doppler. Plus, “being able to do things digitally and capture images digitally has been a huge improvement in workflow,” she says. Since images go to the network immediately, the physician can review them as they’re being acquired.
Great things ahead
Echo innovation includes smaller and smaller equipment. Eyal Herzog, MD, FACC, director of the Cardiac Care Unit at St. Luke’s-Roosevelt Hospital Center in New York City, has been testing the Acuson P10, a pocket-size ultrasound system from Siemens Medical Solutions. The system weighs 1.6 pounds and its emergency applications include FAST (focused assessment with sonography for trauma) to detect fluid, determining cardiac activity and pericardial effusion, as well as detecting abdominal aortic aneurysms and performing pelvic exams.
Herzog has submitted for publication a paper about his research comparing the P10 to high-end echocardiography machine—he found equivalent image quality. The P10 is going to have Doppler flow and color within a year which he says “will be an unbelievably nice tool.”
Herzog says the evolution of echocardiography from a large machine to something you can carry in your pocket has been amazing. “It’s changed the way we practice cardiology conceptually. We can look at what we used to listen to or estimate. We can see it in a noninvasive approach. It may replace the stethoscope.”
Carr is looking forward to learning more about cardiac 4D imaging. “That’s going to be an exciting thing coming up. I see that being a useful tool down the road.” That could be used for looking at holes in between the heart chambers or to look at valves, particularly the mitral valve for a leak or prolapse. “There are great things ahead for ultrasound.”