Cardiac sonography, commonly known as an echocardiogram or “echo,” is a non-invasive diagnostic procedure that uses sound waves to create moving pictures of the heart. This painless test provides a real-time view of the heart’s anatomy and function, allowing doctors to observe how the muscle, chambers, and valves are working. A specialized healthcare professional called a cardiac sonographer performs the imaging, and a cardiologist interprets the resulting images.
The Science Behind the Image
The mechanism behind cardiac sonography relies on ultrasound technology, which employs high-frequency sound waves. A handheld device called a transducer is placed on the chest wall, emitting these waves into the body, typically operating in a frequency range of 2 to 12 megahertz. These sound waves travel until they encounter a boundary between tissues, such as a heart chamber, a valve, or moving blood cells.
When the sound waves strike these structures, they bounce back as echoes to the transducer, which acts as both a transmitter and a receiver. The system’s computer measures the time it takes for the echoes to return and the strength of the signal. This information is used to calculate the distance and density of the heart structure, compiling the data into a dynamic, two- or three-dimensional image displayed on a monitor. Specialized Doppler techniques use the change in the sound wave’s frequency, known as the Doppler shift, to map the speed and direction of blood flow through the heart’s vessels and valves.
Why Doctors Order This Test
The primary purpose of ordering a cardiac sonogram is to gain a detailed assessment of the heart’s pumping capabilities and structural integrity. A frequent application is measuring the heart’s ejection fraction—the percentage of blood leaving the left ventricle with each contraction—which gauges heart muscle function. The test also allows for evaluation of the four heart valves, checking for issues like stenosis (a narrowing that restricts blood flow) or regurgitation (a leak that allows blood to flow backward).
Doctors use this imaging to measure the size of the heart chambers and the thickness of the heart walls, aiding in the diagnosis and monitoring of conditions like heart failure or cardiomyopathy. The sonogram can also detect pericardial effusion (fluid around the heart) or identify blood clots. It is a standard tool for investigating symptoms such as chest pain, shortness of breath, or heart murmurs, and for assessing damage following a heart attack.
Different Ways the Test Can Be Performed
While the term cardiac sonography often refers to the standard procedure, there are several distinct variations designed to capture different types of clinical information.
Transthoracic Echocardiogram (TTE)
The most common form is the Transthoracic Echocardiogram (TTE), where the transducer is placed on the outside of the chest wall. The TTE is entirely non-invasive and serves as the routine method for initial diagnosis and general heart assessment.
Transesophageal Echocardiogram (TEE)
This specialized technique is typically performed when TTE images are not clear enough or when detailed images of posterior structures, like the atria and the aorta, are needed. The patient is sedated, and a thin, flexible tube with a tiny transducer is guided down the esophagus. Since the esophagus sits directly behind the heart, this approach provides much higher-resolution images without obstruction from the ribs or lungs.
Stress Echocardiogram
This variation evaluates the heart’s function under physical duress. The procedure involves taking ultrasound images before the patient performs controlled exercise, usually on a treadmill or stationary bike. Immediately following the exercise, a second set of images is taken to compare the heart’s function at rest versus when working hard. If a patient cannot exercise, medication can be administered to simulate the effects of physical exertion.
What to Expect During the Procedure
For a standard Transthoracic Echocardiogram, preparation is minimal, and patients are generally able to eat, drink, and take their usual medications beforehand. Upon arrival, the sonographer will ask the patient to change into a gown and lie on an examination table, typically turning onto the left side to bring the heart closer to the chest wall. Electrodes are attached to the chest to monitor the heart’s electrical activity throughout the test.
The sonographer applies a warm, lubricating gel to the chest area, which is necessary to ensure the sound waves travel efficiently between the skin and the transducer. The transducer is pressed firmly against the chest and moved to various positions to capture images from different angles. Patients may feel a mild pressure from the probe and might hear whooshing sounds, which are the Doppler function recording the movement of blood. The entire procedure is painless and usually takes between 45 and 60 minutes.