Like the Beat, Beat, Beat of a Tom-Tom: Listening to the Heart's 'Voice'

"Echocardiology is a very exciting field these days," says cardiologist James P. Eichelberger, M.D., assistant professor of medicine. "Thanks to recent advances in technology, we can answer more and more questions raised by our referring physicians." Along with Dr. Karl Schwarz, the Director of the Echocardiography Laboratory and Dr. Gladys Velarde, Dr. Eichelberger, the other echo physicians provide state of the art echocardiography services. "We get many referrals from our other cardiology colleagues in the community, especially if there is a very difficult study involving congenital defects of the heart or replaced heart valves, says Dr. Schwarz. "This is very flattering to us as it means our colleagues really recognize the high level of quality and expertise we provide."

"What makes our lab special," says Cindy Hector, Chief Cardiac Sonographer of the Echocardiography Laboratory, "is that one of our three attending echocardiologists is on hand throughout the procedure. At most labs, the attending reads the results of the test at the end of the day, after the sonographers have gone home and the patient is long gone. Our doctors are right here. They read the report in the patient's presence, consult with the sonographer, and can acquire additional images if they're needed. We're very patient-friendly, and we're proud to say that the quality of our work is very high."

Four types of echocardiography are available, each answering specific questions about the heart and its function: M-mode, two-dimensional, spectral Doppler, and color Doppler.

¥ In M-mode (historically one of the first forms of echo used diagnostically), a stationary ultrasound beam is directed at a predetermined area of the heart. Subsequent scans are made of surrounding areas until every surface has been explored and imaged.

¥ Two-dimensional (or cross-sectional) imaging - preferred now over the M mode - results in spatially correct images of the heart recorded in "real time" on videotape or digitally, enabling cardiologists to identify many cardiac abnormalities.

¥ Doppler echo, including color Doppler, uses ultrasound to record the flow of blood within the cardiovascular system, charting velocity, direction, and type of flow. Doppler studies enable the cardiologist to evaluate for valvular dysfunction or other hemodynamic abnormalities.

What Color Doppler Can Do

"The Doppler echocardiogram provides the doctor with hemodynamic information essential to managing the patient's care effectively. That's why it's one of the most frequent tests ordered," says chief sonographer Hector. "at the Medical Center, we have a cadre of seven sonographers, highly trained to ensure that our measurements are accurate."

The exam has three components: two-dimensional imaging, spectral Doppler (which measures velocity of blood flow), and color Doppler (which reveals directional information, pressure gradients, and valve areas). In color Doppler, each kind of blood cell is coded with a certain hue, depending on the direction of flow relative to the transducer. Blood cells moving toward the transducer are coded red; those moving away, blue. This coding enables the cardiologist to examine the heart from many perspectives.

"We know that blood should flow from the atrium to the ventricles," says Hector. "If mitral regurgitation is occurring, if there's a leak that allows blood to move back across the mitral valve, we'll see blue going into the left atrium. We can gauge the severity of the leak by a number of different measures, such as seeing how far back the jet goes, relative to the size of the left atrium. Color also helps us identify leaks through the walls of the heart."

Transesophageal Echo: Exploring the Heart's Hidden Corners

A newer and more specialized ultrasound test, transesophageal echo (TEE), uses a transducer at the end of a gastroscope to image the heart through the adjacent esophagus, bringing into view areas of the heart once obscured by structural barriers imposed by the transthoracic technique.

"The development in recent years of transesophageal echocardiography has been a big breakthrough in imaging," says Hector. "In some patients, it's difficult to see the areas of cardiac concern because they're hidden." Now, using a TEE, cardiologists can examine those elusive corners of the heart.

"The development of transesophageal echo has transformed our ability to take care of acute problems like dissecting aneurysms of the aorta," says George H. Hicks, M.D., chief of cardiothoracic surgery at the Medical Center. "Now we can clearly see when a dissection is present, and have the patient in the operating room within an hour of diagnosis."

An extra benefit of TEE is that it's easy to administer, even on a patient in the operating room, an intensive care unit, or a hospital bed.

That's especially important in looking at an aortic dissection, a tear in the main artery coming out of the heart, a procedure for which TEE is now the gold standard, and in which fast action is needed. "It used to be that CAT scans or angiograms were the first choice in this situation, but now with improved imaging TEE is preferred," says Dr. Eichelberger. "We can do the test in 15 minutes at bedside on a critically ill patient who otherwise would have to be transported to radiology."

The Stress Echo Test

"Cardiac stress testing has evolved considerably over the last 15 years," says Dr. Eichelberger, "and now includes a form of stress testing that uses echocardiography to improve diagnostic accuracy. Imaging the heart with ultrasound immediately after a period of stress, such as on a treadmill, can bring out abnormalities in wall contraction that are the signal of a significant coronary artery narrowing."

Advantages of stress echo over other stress-testing modalities include improved accuracy, safety without exposure to radiation, cost compared to other forms of augmented stress testing, and ability to give additional cardiac information, such as change in valve function with exercise or other exercise-induced changes in cardiac hemodynamics.

"The main limitation of a stress echo test arises when bone or lung limits the acoustic 'window,'" says Dr. Eichelberger. "In that case, a nuclear stress test might be more appropriate if some form of augmented stress testing is desired. Often we can predict in advance of a test how good the images will be by having the patient lie on his or her side and manually palpating the apex of the heart. A palpable heart apex usually signifies adequate image quality."

Training Facilities
The Echocardiography lab is a digital acquisition imaging lab.  Imaging services are offered in house at the lab and portably.  Offsite imaging services are offered at an outpatient services center and as part of a mobile cardiovascular imaging service.  Image reviewing stations are located in the lab and at our offsite outpatient center.  Current imaging equipment from Siemens and GE offer the most current and up to date ultrasound imaging modalities available.