A heart ultrasound, also known as a cardiac ultrasound, or an echocardiogram, is an important imaging tool that doctors use to perform routine check-ups on patients.
It is also used in critical, emergency situations to help save lives! High frequency sound waves, also known as ultrasound, are transmitted into the body by a small transducer, reflected back, and then processed in the ultrasound machine to create diagnostic pictures and videos of the heart. Cardiac ultrasounds are performed by diagnostic cardiac sonographers, or cardiovascular technologists. These tests are performed independently by the technologist and then reviewed by a doctor, specifically a cardiologist.
TYPES OF HEART ULTRASOUNDS
1. TWO-DIMENSIONAL, TRANSTHORACIC ECHOCARDIOGRAPHY
Due to the dynamic nature of the beating heart, cardiac ultrasound is used in a myriad of ways to assess cardiac disease. At the most basic level, two-dimensional images are created and used to assess heart structure. These images are made through a continuous wave of ultrasound being transmitted and reflected. With these images, technologists will measure the size of the heart chambers, the heart muscle, and the great vessels. Two-dimensional videos, also known as cine loops, are then used to assess heart function. With these videos, cardiologists can determine how well the heart muscle is squeezing and if it’s pumping enough blood to the rest of the body.
Doppler, much like the weather Doppler we see on the news, allows technologists and doctors to assess blood flow through the heart. With Doppler, it is possible to visualize the direction that blood is moving and calculate how much blood is flowing at any given time. There are different types of Doppler that exist in order to achieve certain images and originate certain types of information.
For example, continuous wave Doppler will continuously send and receive pulses of ultrasound to a certain region of the anatomy. This allows the sonographer to assess blood that is moving at a high velocity. On the other hand, pulsed wave Doppler is used to assess a very specific section of blood flow, and does so by sending and receiving signals, one at a time, from an exact location. Pulsed wave Doppler is used to calculate volumes of blood flow and create a visual representation of blood flow that is mapped and represented by specific colors, typically red and blue.
2. 3D DIMENSIONAL ECHOCARDIOGRAM
As technology grows and advances, three-dimensional cardiac ultrasound has developed and allows technologists and physicians to see more accurate visual representations of the heart. With 3D ultrasound, volume measurements can easily be made and more detail regarding heart valve structure and function can be derived. 3D images are particularly helpful for cardiothoracic surgeons who are performing valve replacements, or repairs.
3. TRANSESOPHAGEAL ECHOCARDIOGRAM (TEE)
Cardiac ultrasound is commonly used by means of imaging through the patient’s chest, also known as a transthoracic echocardiogram; however, it can even be used in a patient’s throat! This test is called a transesophageal echocardiogram, where a thin tubed with an ultrasound transducer on the end is inserted into a patient’s throat. This test is used when a transthoracic echocardiogram falls short. During this test, the ultrasound transducer is extremely close to the heart, which makes the image resolution superior.
4. STRESS TESTING ECHOCARDIOGRAM
Last, but not least, cardiac ultrasound is also used in stress testing. Stress testing allows doctors to assess the heart function and blood flow at higher heart rates. Patients are asked to run on a treadmill at specific speeds and elevations. Cardiovascular technologists, or cardiac sonographers, will take images of the heart before and after exercise. For patients who cannot exercise due to physical ailments or lung disease, medications can be injected that simulate the exercise response and cardiac ultrasound images are taken simultaneously.
GLOBAL LONGITUDINAL STRAIN
One of the most exciting advancements in cardiac ultrasound is the use of global longitudinal strain. This function allows for assessment of the longitudinal function of the heart muscle. Before strain, it was only possible to evaluate the lateral motion of the heart muscle. Due to the fact that the heart muscle contracts in three different directions, this meant that there was significant heart activity that wasn’t able to be evaluated. This longitudinal assessment is important because it allows us to predict heart failure before it even happens! This is very important for patients with breast cancer that are undergoing chemotherapy, as it allows us to ensure that the heart muscle is not being negatively affected by the chemotherapy medications. Global longitudinal strain is a form of pulsed-wave Doppler and is now being used in a wide array of diagnostic assessments.
In conclusion, cardiac ultrasound is an invaluable tool that allows doctors to diagnose and assess a wide variety of cardiac and systemic disease. With cardiac ultrasound it is possible to assess structure, function, and make accurate measurements down to a millimeter! Although cardiac ultrasound has advanced exponentially in the last fifty years, it is expected to continue to develop and provide new life saving technologies for patients.
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