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What is an Echo?
An echocardiogram, or cardiac echo, is an ultrasound of the heart. It uses the same technology that is used to look at babies before they are born. The sonographer holds a small probe against your skin and uses it to create moving images of your heart. The pictures are displayed on a computer screen.
Ultrasound is fantastic for looking at overall heart anatomy, heart murmurs, and how well the muscles of the heart contract. There is no radiation and no needles. You get to lie down and relax while the scan is performed. Some patients even fall asleep during their echo.
Does an echo tell us everything?
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No. Looking at the heart with ultrasound is a lot like looking at a used car in a sales yard.
We can tell what size and shape the heart is, and whether or not it has had any major accidents. We can take a peek inside and see the basic design (seats, trunk capacity and steering wheel position), and we can assess whether or not the 4 main heart valves open and close normally (a bit like car doors). However, just as looking at a car from the outside does not tell you everything you need to know, an echo will not reveal every type of heart problem, so you may also need other tests.
For example, the heart arteries are so tiny that they will not show up on your echo, so we cannot directly comment on how diseased they are. You can be well on your way toward having a heart attack (which is caused by blocked arteries) but still have a normal echo right up until the point when sections of heart muscle get so oxygen starved that they stop working properly.
We also cannot check the electrical system of the heart. Using the car analogy again, some cars look structurally perfect, but have intermittent electrical problems, such as stalling or failing to start occasionally. Similarly, if you get occasional palpitations or dizzy spells you might still have a heart problem even if your echo images look normal. In medicine (just like in car care) we use different equipment to look for different problems.
What CAN be diagnosed with Echo?:
Overall anatomy: including assessing the size and shape of the heart structures, and determining whether the chambers, valves and large inflow and outflow vessels are all connected up properly.
Heart murmurs: identifying holes in the heart, or noisy problems such as leaking or blocked valves.
Heart muscle function: we can measure how strongly the heart is able to contract, and identify the degree of damage after a heart attack. Echo can also identify problems with muscle elasticity.
Pressures and volumes: Echo can be used to estimate the blood pressure in the lungs or to determine the overall fluid needs of patients in intensive care.
Unwanted extras: such as bacterial or fungal infections inside the heart, fluid around the outside of the heart, or the presence of clots or tumors. Often Echo is used to screen for certain causes of stroke.
How does an echo work?
The sonar technology we use in ultrasounds was initially developed to look for enemy submarines during World War II, but it has been greatly refined since then.
Canadian sailors operating ASDIC, an early form of SONAR – Photo by William H. Pugsley- National Archives of Canada- PA-139273 Image Courtesy of http://www.nww2m.com
We transmit pulses of sound waves into the body and then measure the echoes that are reflected back by the internal organs. The delay between the transmission of the sound and the return of its echo tells us how far away the reflecting tissue was, and the strength of the echo tells us a little about the characteristics of that tissue. Our machines process all this information and create very detailed pictures.
Just like the sound waves used by bats to “see” in the dark, the sound signals we use for diagnostic ultrasounds are too high for the human ear to hear, and cannot cause any tissue damage.
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Ultrasound waves are not in any way radioactive, and are therefore much safer than x-rays. Ultrasound is also much better than x-rays at providing detailed information about soft tissue structures. The main drawback of ultrasound is the fact that it cannot pass easily through soft tissue if there is bone or air in the way.
Other Types of Echocardiograms.
Even with a very skilled sonographer, it is sometimes impossible to get good pictures using normal echo technology. Very occasionally the sonographer may require a patient to have an injection of reflective micro-spheres to enhance the echo images by briefly making the internal borders of the heart more visible. This is an expensive, but very safe way to improve the quality of the scan.
Heart ultrasounds are usually performed on resting patients, however sometimes it may be useful to see how the heart looks during exercise. This is called an exercise stress echo. Patients who cannot physically exercise may sometimes be scanned before and after administration of a drug that mimics the effects of exercise by temporarily causing the heart rate to increase.
Some studies will use specialized probe to create three dimensional images.
It is also occasionally necessary to view the heart in closer detail from inside the body. This is achieved using a specially shaped probe that goes down your throat and sits behind the heart in the oesophageus (the food tube) while pictures are taken. This is called a trans-oesophageal echo. This type of echo usually requires a degree of light sedation and a numbing throat spray to help prevent gagging.
I would like to thank Miriam Norman for Part I of here fantastic articles on Echocardiograms. These articles are written with the patient in mind but the author hopes that healthcare professionals will find inspiration within her posts for ways to communicate with their patients.
Miriam works at the the Royal Hobart Hospital in Australia. Her qualifications include an MSc (clinical physiology), Dip. of Med. Ultrasound (cardiac) and IBHRE (cardiac devices). She is also also a part time musician with the Tasmanian Detachment of the Royal Australian Navy Band.
In Miriams next post read what to expect from an echocardiogram.