Even though echocardiography has been the most widely-used diagnostic test for heart disease for more than 50 years, it’s more than keeping up with, even exceeding the benefits of, other imaging modalities. With better resolution than MR and CT, powerful and portable devices, and new research and theories, the echocardiogram is poised to take a starring role in screening and diagnosing heart disease.
Echo for annual exams
John Postley, MD, a cardiologist with New York Physicians Group, performs more than 2,000 echocardiograms a year using the handheld MicroMaxx from SonoSite. Postley recently presented his findings that vascular ultrasound screening can be a more accurate means of risk stratification for heart attack, particularly among women, than the Framingham Risk Score, which has been the traditional method of identifying cardiovascular risk. He used the device to look for the presence of carotid and femoral arterial plaque and the measurement of carotid intimal medial thickness (CIMT).
“We’ve been struggling with what is the relationship between plaque and CIMT,” he says. One thought was that a lower CIMT measurement is the first stage of developing plaque. Research has shown that they are probably separate problems, however. Regardless, clinicians can use echo to analyze both.
Since 800,000 Americans have a first heart attack each year and 40 percent die, 250,000 people are dying without even knowing they were sick, Postley says. He advocates making screening echocardiograms part of annual exams, especially because of the superior resolution offered. “The limit of resolution of MR and CT is no better than 1.5 or two millimeters.” Echo is 10 times more subtle, allowing clinicians to catch much more when it comes to changes and abnormalities.
Supporting Postley’s recommendation is the recent CAFES-CAVE Italian study, which found that looking at CIMT in the four carotid and femoral arteries, outside of the heart, predicts with 98.5 percent sensitivity who will have a heart attack or stroke. “You’re better off looking outside of the heart if you have the technical expertise,” he says. He has that expertise: with the SonoSite MicroMaxx, Postley can look at those four vessels “with astounding resolution” in 14 minutes.
Postley acknowledges the “turf war” that many radiologists and cardiologists experience. “We’re not pretending to be radiologists,” he says. “We can be good partners with radiologists.” If Postley finds a problem via echo, “I immediately refer patients for another study, usually MR or contrast CT, to work out the abnormality.”
Stat in the ICU
Yanick Beaulieu, MD, of the Division of Cardiology and Critical Care Medicine at Hôpital Sacré-Coeur de Montréal, is using handheld, portable echocardiography from SonoSite at the bedside in the intensive care unit. “It’s an important place for echo,” he says. “Every day there’s a situation that dictates an emergent or semi-urgent echo in the ICU.”
As an intensivist and cardiologist, Beaulieu splits his time between the ICU and his cardiology practice. There are different indications for echo in the ICU. Either a patient isn’t doing well from the start or starts to decline, usually because of low blood pressure. There are many causes for that and Beaulieau points out that knowing whether the cause is heart-related or not is a big help. An echocardiogram can quickly show him if there is fluid around the heart, whether the patient has had a heart attack, or whether a pulmonary embolism or other problem with the lungs is straining the heart.
About four years ago, Beaulieu was doing his critical care fellowship when the program’s director purchased a handheld unit. He found the device “addictive.” He has found that patients in ICU or emergency departments “have all kinds of pathologies and a physical exam is not always helpful. We need more information that cannot be provided by physical examination.”
The handheld unit isn’t meant to do everything a larger device can — it’s really a screening tool, Beaulieu says. His hospital has three MicroMaxx devices. Other clinicians and residents use one in the ICU to screen the heart for right and left side function, and putting in lines and drains. A device in the OR assists surgeons with central line access and regional nerve blocks.
Quick EF and volumes
Navin Nanda, MD, professor of medicine and director of the Heart Station/Echocardiography Laboratories at the University of Alabama at Birmingham, recently received an upgrade to his Sequoia echocardiography system from Siemens Medical Solutions that features velocity vector imaging (VVI). VVI allows clinicians to see a graphical presentation of tissue motion using vectors to display direction and relative velocity of motion in one ventricle in 2D echo in real time, with the ability to see a “freeze frame” of motion at any point in the cardiac cycle. Quantification of these vectors throughout the cardiac cycle enables measurement of new indices of ventricular function. This enables clinicians to easily visualize both contraction and relaxation mechanics and offers a new method for assessing cardiac function.
That helps Nanda and his colleagues get a very good idea of a patient’s ejection fraction (EF) and volumes very quickly. “Sometimes it takes a long time to figure out EF,” he says. “We’re finding this very useful in day-to-day practice.” Patients with an EF of 35 percent or less aren’t good candidates for a biventricular pacemaker. Making that determination with echo can help Nanda efficiently start to focus on other treatments.
Echo offers an objective way of looking at two opposing walls and seeing whether they move in the same or opposite directions. “We want to make sure the opposing walls are moving in opposite directions,” Nanda explains. He uses echo to see which direction each point on the wall of a ventricle is moving, from the beginning of the cardiac cycle to the end. He can see how fast the wall is moving and whether it is moving normally. Seeing this with other modalities is more difficult and can be more subjective.
Nanda has found that echo is a good tool for a lot of patients. For example, MRI isn’t possible for pacemaker patients. Plus, echo is cheaper so it can be used in physician offices, not just large hospital settings. That can make it a lot more convenient for patients.
Imaging tiny hearts
Pediatric cardiologist Girish Shirali, MD, at the Medical University of South Carolina in Charleston, uses echocardiography equipment from Philips to diagnose congenital heart disease.
Three-dimensional echo has been the most significant advance for Shirali. “That’s been a very, very exciting advance for us. That’s really the place we’ve been putting a lot of our energies in our lab — live, 3D echo.” Oftentimes, clinicians can see things in two planes with 2D echo but still have to reconstruct the third plane. “With 3D echo, you can see those things yourself on the screen rather than having to go through this major mental process,” he says. “Also, it turns out that the conventional 2D images and viewing perspectives we’ve had are not necessarily the same that the surgeon has.” The vast majority of children end up getting surgery without heart catheterization. The surgery is based on echo findings alone, so the accuracy of the echo is critical. Now, Shirali can show the surgeon exactly what the heart defect will look like.
3D allows Shirali to quantify the function of the ventricles more accurately. That takes more work and doesn’t save time, but it does result in more of a complete picture. “There has been a major move towards being able to quantify the function of the heart and valves better than we were able to before,” Shirali says. Using tissue Doppler, he can look at the speed with which the heart muscle moves. That reflects the function of the entire ventricle.
Other advances are important to some of Shirali’s patients. He images patients whose size can vary from a little over one pound all the way up to the adults who have survived childhood disease. That variation requires a wide range of frequencies and penetration. Children under age three need to be sedated and that means the echocardiographer has a limited time to perform the study. “The person doing the study really needs to know what they’re doing and move fast. The sedation medication only lasts a certain amount of time,” explains Shirali. The tiniest babies require that the transducer used isn’t too heavy. They actually can weigh more than the patient.
Shirali has been in practice since 1994. Other than 3D, the biggest echo advances he has seen since then have been in computing power and miniaturization. “We’re able to get images at a higher rate. The frame rates are much higher with the current technology, which is particularly important for babies with fast heart rates.” Meanwhile, the transducers have gotten smaller and lighter which has important ergonomic implications for sonographers.
Shirali thinks echo is very helpful for preoperative planning, and not just for the surgeon. “It helps [the surgeon] discuss specifics with the family and it helps in having the entire operative team all on the same page when they go in. Our job is to provide the surgeons with as much information as we can give them to make that OR stay for patient and surgeon as stress-free as possible. We believe that is going to result in better outcomes.”
Shopping for information
Inland Cardiology Associates, a practice with five locations in eastern Washington and northern Idaho, installed the compact Xario from Toshiba about a year ago. Since then, it has been used for patients with a wide range of symptoms, including unexplained chest pain and heart murmurs. Cardiovascular sonographer Craig Bartholomew has found that echo is helpful in planning treatment for congestive heart failure, including assessing the level of shunting needed and pinpointing abnormal anatomy for subsequent surgical repair. “Echo shows a high level of tissue characterization and diffuses slices through more structures in real time compared to other modalities.”
Bartholomew has been impressed with the images he can get, especially with an increasing number of overweight patients. “I get higher quality pictures on harder-to-penetrate patients with ultrasound.”
He particularly appreciates the ability to study structures in real time. “You can watch the heart as it’s beating and cut an unlimited amount of planes just by angling the probe.” With other modalities, you can’t see an unlimited number of heartbeats while deciding what to take pictures of, he points out. With echo, “you can do a lot more shopping and get more information that way.”
With an aging population, echo will be a cost-effective way to provide care. “The longer you live, the more things are going to deteriorate,” says Bartholomew and echo is a relatively easy and safe way to find problems.
With the ongoing focus on heart disease and an aging population that is sure to face more heart conditions, echocardiography vendors are fine tuning their products. Beaulieu expects “even a higher quality of image. Right now, we see many artifacts by the rib cage and lungs when performing echocardiography.” Because ultrasound doesn’t penetrate bone or lungs well, he thinks we’ll soon see technology that filters artifacts better.”
Devices even smaller than today’s handhelds may become available but Beaulieu says they can’t be too small or physicians won’t be able to see the images. More likely are lighter devices with more functions.
Another potential change for echo is the use of contrast agents to help asses how the heart squeezes, says Bartholomew. Contrast agents would allow for better viewing of left ventricular function.
Researchers also have been working for about the last decade on finding a way to use some type of medium to assess perfusion of the heart by seeing how it deposits blood in the muscle. That is similar to other scans, Bartholomew says, but doesn’t use radioactive isotopes like a nuclear scan does.