Echocardiography's expanding role in cardiovascular diagnosis and management

March 07, 2017
by Sridhar Nadamuni, Contributing Reporter
Heart disease is the leading cause of death in the U.S. Evaluation of the cardiovascular system using ultrasound (US) waves is noninvasive, and facilitates clinical assessment, diagnosis and management of abnormal valves, atrial fibrillation, heart disease and heart murmurs. Studies suggest that nearly 34 million echocardiography procedures were performed on Medicare beneficiaries in the U.S. between 2007 and 2011. Annually, almost 20 percent of enrollees in the fee-for-service (FFS) system receive at least one cardiac echocardiogram. Research suggests that the U.S. imaging equipment market is projected to top $2 billion by 2020, with cardiology and radiology ultrasound equipment sales accounting for 50 percent of the total.

Point-of-care ultrasound device sales are slated for significant growth in the future, driven by new, radiation-free needle placement procedures. “We have seen tremendous development in technologies such as 3-D and strain imaging that are now more mainstreamed, easier to apply, not just for research, but also in routine clinical work, and their use has been validated in the literature,” says Smadar Kort, M.D., FACC, FASE, FAHA, professor of medicine and director of echocardiography at Stony Brook University in New York. “The volume of echocardiograms performed at Stony Brook has definitely increased over the last 10 years, and continues to increase, reflecting the trends elsewhere in the U.S.”

Echocardiography is considered by physicians such as Dr. Kort as the safest, cheapest and quickest noninvasive imaging modality available. It facilitates diagnosis at the bedside, the ICU and the ED. The growth in utilization of echo has been driven by the development of new interventions in both the cath lab as well as the electrophysiology (EP) lab, which rely heavily on echo to identify the appropriate candidates for these procedures, as well as to guide those procedures in real time, says Dr. Kort.

“The requirements for preauthorization, reduced reimbursement for the more expensive, advanced imaging studies, coupled with advances in echo have shifted the utilization more towards echocardiography,” says Dr. Kort, who is also the director, Valve Center, and director of noninvasive cardiac imaging at Stony Brook University. “The need to minimize or avoid radiation exposure from diagnostic imaging has made the field attractive to the patient and caregivers alike,” says Sharon Mulvagh, M.D., FRCP(C), FACC, FAHA, FASE, emeritus professor at the Mayo Clinic in Rochester, Minn., and professor of cardiology at the Dalhousie University Department of Medicine at the Nova Scotia Health Authority in Canada.

“Electrocardiography is the mainstay of cardiac diagnosis, and the frequency of its usage far outweighs that of CT scans and MRIs,” says Milind Desai, M.D., a staff cardiologist in the Section of Cardiovascular Imaging in the Robert and Suzanne Tomsich Department of Cardiovascular Medicine at the Sydell and Arnold Miller Family Heart & Vascular Institute at Cleveland Clinic. Over 70,000 echocardiograms are done at the Cleveland Clinic annually, and Dr. Desai reads nearly 2,500 echocardiograms, 1,000 cardiac CTs and 300 cardiac MRIs.

Dr. Mulvagh commented that echocardiography is the first choice in cardiac diagnosis as it is “radiation-free, relatively low-cost, portable and available throughout the world, especially for patients who are infirm or fragile.” It has been approved for use in the largest variety of patient cardiac needs.

Dr. Desai explains that ultrasound is used following an initial electrocardiogram (ECG), for instance, when an ECG is normal, but the patient continues to complain of chest pain. Physical examination has poor diagnostic accuracy, and leads to false-negative or false-positive outcomes in detecting cardiac pathology approximately 50 percent of the time when compared with transthoracic echocardiography (TTE) in both the acute and outpatient settings. The most common pathologies missed by clinical examination include aortic stenosis and cardiac failure, which account for nearly 2 percent to 3 percent in the general population and 10 percent to 20 percent in the population age 75 or older.

However, “history and physical examination always come first, and echocardiography is a close second,” according to cardiologist Michael W. Cullen, M.D., FACC, who is affiliated with numerous hospitals, including the Department of Cardiovascular Diseases at the Mayo Clinic. “Echocardiography plays a key role in diagnosing valvular and congenital heart disease, hypertrophic cardiomyopathy and atrial fibrillation.” It is an excellent choice for the determination of cardiac structure and function, and hemodynamic and physiological evaluation as well as in the diagnosis of valvular stenosis and regurgitation, determination of pulmonary filling pressures, stroke volume and cardiac output.

Ultrasound technology offers a standardized, qualitatively superior, broad and reproducible method to ensure the quality, reliability, reproducibility and overview of hemodynamic and intravascular volume status data. It facilitates the determination of the basic venous collapsibility and overall cardiac status as well as the condition of cardiac flow and tissue Doppler signals. Dr. Kort highlighted the advantages, including “low cost compared with other imaging modalities such as CT or MRI, small size of the equipment that does not require [a] special facility, lack of ionizing radiation or use of contrast material that could impact renal function.” Echocardiography performed in a high-quality laboratory is reliable, associated with small variability and allows appropriate follow-up of patients.

Three-dimensional echocardiography (3DE) facilitates data acquisition, dynamic display of functional anatomy of cardiac abnormalities, congenital defects and the possibility of online quantitative analysis of cardiac chambers and heart valves. Transthoracic 3DE has been used to determine cardiac chamber volumes and function due to the lack of geometric assumptions about their shape and the avoidance of apical view foreshortening, unlike the volume calculations derived from 2DE views. Transesophageal 3DE has been used mostly to assess heart valve anatomy and function.

Technological advances and the miniaturization of ultrasound equipment have led to the use of echocardiography in a variety of departments, including critical care and emergency medicine. Technological advances have also improved the imaging quality, making diagnosis with ultrasound more reliable and effective. The market as a whole is driven by cutting-edge, groundbreaking technologies. In addition to market leaders such as GE Healthcare, SonoSite and Philips, companies including Zonare, Hitachi Aloka, Esaote, Analogic, Toshiba, Siemens Healthcare, U-Systems, Terason and Mindray are emerging leaders in ultrasound equipment manufacture and sales.

According to Dr. Kort, major technological improvements in ultrasound include “improved imaging and automated quantifications of valvular stenosis and regurgitation, and assessment and follow-up of the cardio-oncology patient using strain imaging.” It is also the modality of choice for the majority of follow-up studies for assessment of disease progression, she added. Dr. Desai explained how the technology has evolved from M-mode echos in the 1970s and ‘80s, to the far more sophisticated developments involving color overlay over the moving images to highlight the heart valves and areas of leakage.

Hand-held ultrasound (HHU) facilitates the diagnosis and triage of patients presenting with cardiovascular emergencies. “Hand-held machines are utilized for focused applications and are not intended to replace portables or full-sized machines,” says Dr. Mulvagh. “For example, in the context of the clinical assessment of a cardiac patient, hand-held ultrasound functions as an extension of the stethoscope, and can guide diagnosis, testing and management of patients.”

Hand-held devices facilitate visualization of body tissues and vessels during the procedure. According to Dr. Mulvagh, “the image quality of the hand-held devices is comparable to the full-sized machine.” However, current imaging technology involving the hand-held tools is restricted to 2-D and color Doppler. No digital connectivity or image storage is currently feasible, although it may soon be available on a few hand-held devices. Dr. Desai agrees that the hand-held device is a “glorified stethoscope,” but still needed for initial diagnosis in an emergency setting before the patient is referred to a regular echocardiographic screening. “A full-fledged, hand-held probe is still five to 10 years down the road.”

Dr. Cullen still subscribes to his finding reported in the Mayo Clinical Proceedings of June 2014 that “hand-held echocardiography (HHE) tends to underestimate rather than overestimate the severity of abnormal findings,” suggesting that, “HHE should not be used as a surrogate for TTE.” In addition to TTE, stress echocardiography used to unravel cardiac muscle function, 3-D echocardiography and left ventricular strain measurement are driving the market size.

According to Dr. Mulvagh, “the use of echocardiography to guide cancer [assessing chemotherapy or radiation damage to the heart] treatments has also opened a new avenue of diagnosis and encouraged the use of strain echocardiography.”

“Using strain imaging and 3-D echo on patients receiving chemotherapy can identify those at risk for cardiotoxicity, and their prognosis could improve by close collaborative monitoring by cardiologist and oncologist and initiation of cardioprotective medications,” says Dr. Kort. However, the procedure is “operatordependent [technical skill of the person using the probe and recording the images is variable] and reading cardiac ultrasounds requires a technically advanced skill set,” says Dr. Mulvagh.

“The other disadvantage of echocardiography is that images of tortuous structures such as blood vessels in the path of the ultrasound beam may be distorted and yield wrong measurements resulting in an inaccurate estimate of the dimensions,” says Dr. Desai. The 3-D echo is a refined version that overcomes the issues related to tangential measurements, but is still dependent on the 2-D echo, Dr. Desai adds. He also highlighted the appropriate use of contrast echocardiography, for example, in patients that are difficult to image such as smokers and obese patients.

It is recommended for 10 percent to 15 percent of all cases. As Dr. Cullen observed, echocardiography is incapable of providing anatomical detail to the same extent as a CT scan or cardiac MRI. “Muscle perfusion is also not as clear as in nuclear MRI.” Echocardiography is not a stand-alone modality, but an adjunct to other procedures, he added. Dr. Desai’s main concern relates to the potential abuse of HHU devices. “As with any new device, there is a risk of overuse or inappropriate use that could raise the health care costs,” Desai said.

It might be appropriate as a point-of-care intervention for rapid diagnosis in an emergency such as pericardial tamponade or a patient with severe chest pain with fluid build-up despite normal ECG findings. However, “physicians and technicians at corporate hospitals may have a tendency to abuse the modality just to make a fast buck at the expense of the patient, which is undesirable.”

The potential for inappropriate use or over-utilization of echo remains, commented Dr. Kort, who is a member of a writing group representing several professional societies including the ACC and the ASE, which develop appropriate use criteria for multimodality imaging and assessment of cardiac structure and function in patients with both valvular and non-valvular cardiovascular diseases. In her opinion, adherence to guidelines and appropriate use criteria documents can improve proper utilization of echo. “Studies performed in an accredited laboratory tend to be of higher quality, although lab accreditation is not mandatory.”

The biggest challenge, according to Dr. Cullen, is “attracting adequately trained sonographers in a tight labor market” in light of the emergence of novel ultrasound technologies, such as portable and miniature echocardiographic devices providing percutaneous and structural details with 3-D resolution.

The upcoming 28th Annual Scientific Sessions of the American Society of Echocardiography (ASE) to be held in Baltimore June 2-6 will focus on 3-D echocardiography, contrast echocardiography, critical care ultrasound, point-of-care ultrasound and diseases of the aorta. Specifically, innovations will focus on machine learning and robotic echo, new applications of ultrasound physics, Shear Wave imaging, fusion imaging, targeted therapeutic delivery applications in cancer, and target therapeutic delivery in ischemic heart disease, according to Geoffrey A. Rose, M.D., FACC, FASE, chief of cardiology, Sanger Heart & Vascular Institute at Carolinas HealthCare System and the ASE program chair. “Innovative technologies such as ultrasound microbubble-based gene therapy combining imaging and therapeutic applications will be presented at the event.”

“As the technology advances and more data is collected and interpreted, it is critical that reimbursement rates support the longer and more comprehensive scanning and interpretation,” says Dr. Kort. “Echo procedures performed to guide various interventions are notoriously long and poorly reimbursed.”