Indian Academy of Echocardiography

Echocardiography (commonly referred to as echo or 2D echo)

Echocardiography is the broad term which encompasses all different varieties of echo techniques. It can be classified depending on how the images are obtained, what specific techniques are used for creating the images and whether the examination was performed at rest or during some form of stress.

Echo is traditionally performed by placing a probe on the chest wall. This is the form of echo which we all are most familiar with. This is known as transthoracic echo or simply ‘echo’. Some people also call it ‘2D echo’, but this is not the most appropriate term (explained below). Alternately, echo can also be performed by inserting the probe in to the food-pipe just as endoscopy is done (known as transesophageal echo) or, less often, by inserting a catheter in to the heart (known as intracardiac echo).

Each echocardiographic examination involves use of 2D imaging and Doppler (including color Doppler) for visualizing the heart. No echocardiographic study will be complete without the use of these techniques. In addition, depending on the equipment, expertise of the echocardiographer and the clinical need, additional techniques such as 3D imaging, tissue Doppler and strain, contrast imaging, etc. may have to be used.

Echocardiography is mostly performed at rest, but in many clinical situations, it may be combined with some form of stress such as exercise or a medication to speed up the heart beating. This is known as stress echocardiography.

The subsequent discussion refers to traditional echo performed at rest.

No, a resting echo doesn’t show us the blockages, unless the blockages have already caused damage to the heart muscle. In other words, if a part of the heart muscle is damaged, it indicates blockage in the artery supplying blood to that part of the heart muscle. However, if there is no apparent damage to heart muscle, then the blockages may or may not be present.

Stress echocardiography (as discussed below) is the test specifically designed to detect blockages in the heart arteries.

How is the test performed? What will I experience during the test?

No, echo is not painful but you will feel slight pressure from the echo probe being placed on your chest wall. The pressure of the echo probe on your chest wall may cause slight discomfort. This discomfort is only mild and subsides on its own.

Echo is a completely non-invasive test, which means no needles, catheters, or dyes are used. However, on rare occasions, when ultrasound images are difficult to obtain because of body structure, contrast imaging may be needed. This will require an intravenous line to be placed which will cause slight pain.

Contrast echocardiography

What is contrast made of?

The agitated saline, as mentioned above, is nothing but vigorously shaken saline solution (the clear liquid used for intravenous drips). Vigorous shaking traps air within the liquid, forming small bubbles.

The ultrasonic contrast agents are engineered microbubbles which have an outer shell (composed of a protein or a lipid) with small amount of gas inside.

The procedure of contrast echocardiography is almost the same as any standard echocardiography test except that small amount of contrast solution is injected during the test. Of course, an intravenous line will have to be placed for injecting the contrast.

Transesophageal echocardiography

The TEE test is performed under local anesthesia. In some patients who are quite anxious and are unable to tolerate the procedure, sedation may have to be used. For this, a medicine is given by injection which makes the patient sleepy. At some centres, sedation is used routinely.

Regardless of whether sedation is used or not, a local anesthetic will be sprayed to numb the back of your throat and you will also be asked to swallow one or two spoonsful of a local anesthetic liquid. In addition, a local anesthetic gel will also be applied to the tip of the transducer. Once the throat is adequately anesthetized, the TEE probe will be gently inserted into your mouth and directed into your food-pipe. If you are not sedated, you will be asked to swallow as the probe is inserted, which makes it easier to guide the probe in to proper position.

Once the probe is appropriately positioned, images of the heart will be taken from different angles and views, following which the transducer will be taken out. The entire process will take around 10-15 minutes only. Your heart rate, blood pressure and blood oxygen level will be monitored during the test.

Do I need any specific preparation for the test?

Yes, several important precautions need to be taken-

• You should not eat or drink anything for at least 6 hours before the test. Only clear liquids may be allowed up to 3 hours prior to the test.
• If you have a loose tooth, you need to tell the doctor about it. If you use dentures or dental prostheses, they may need to be removed before the test.
• You should also tell the doctor or nurse if you have a problem with swallowing or have a history of any disease related to your food-pipe or stomach of if you have any bleeding disorder. If you are taking any blood thinners, they may have to be stopped before the test.
• Tell your doctor or nurse if you have any allergies to medicines, especially medicines that make you relax.
• If you have diabetes and take medications to manage your blood sugar, ask your doctor how to adjust your medications on the day of your test.
• If you are undergoing TEE under sedation, you will not be able to drive until the day after the procedure. Hence, you should bring someone with you to drive you home after the test.

The TEE test itself is not painful but if an intravenous line needs to be secured, that will hurt slightly.

The anesthetic sprayed into your throat may taste bitter and will make your tongue and throat feel numb and swollen. Some people report that they feel as if they cannot breathe at times because of the probe in their throat, but this is a false sensation caused by the anesthetic. There is always plenty of breathing space around the probe in your mouth and throat. Remember to relax and take slow, deep breaths.

You may gag and feel nauseous, bloated, or have mild belly cramps when the probe is moved. If the discomfort is severe, alert your doctor with an agreed-upon signal or a tap on the arm. Even though you won't be able to talk during the procedure, you can still communicate.

Sedation, if used, will of course make you feel sleepy. You may also feel heaviness of eyelids, trouble speaking, a dry mouth, or blurred vision. These effects may last for several hours after the test but you probably will not be able to remember much of the test.

You will be advised not to eat or drink for at least an hour after the procedure.

You may have a tickling sensation in the throat, dryness of the throat, slight hoarseness of the voice or a mild sore throat. These symptoms may last for 2 to 3 days. Throat lozenges and warm salt water gargles can help relieve these symptoms. Throat lozenges can be used by people age 4 or older. And most people can gargle at age 8 and older. If the symptoms do not improve with time or if you have too much discomfort, then contact your doctor immediately.

Exercise stress echocardiography

You need to be fasting for roughly 3 hours before the test. You should wear comfortable two-piece clothing and shoes that you can walk rapidly in. You may be asked to change into an exam cape/ gown to wear during the procedure.

You should disclose all your medical details and medications that you are taking to the doctor performing the test. The doctor will advise you if any particular cardiac medicine needs to be stopped prior to the test and will also advise you what to do about the diabetes medicines. If you have a history of asthma and use an inhaler for breathing, bring it to the test.

In case of men, you will also be required to shave your chest because ECG electrodes will have to be placed on the chest wall.

Before the test, a cardiac sonographer will fix several ECG electrodes (small, sticky patches) on your chest wall. These are required for recording your heart rhythm during the test and for acquiring echo images. A resting ECG will then be performed and your heart rate and blood pressure will be recorded. If contrast is going to be used, then an intravenous access line will also be secured. A resting echocardiogram will then be performed.

Before you start exercising, the sonographer will demonstrate you how to walk on the treadmill and how to promptly return to the exam table once the exercise is over. You will then be asked to exercise on the treadmill under supervision. Your heart rate and blood pressure will be monitored and at regular intervals, the lab personnel will ask you how you are feeling. If you feel chest, arm or jaw pain or discomfort or become short of breath, dizzy or lightheaded, or have any other unusual symptoms, tell the lab personnel immediately.

When you feel you are not able to exercise any further, the treadmill will be stopped. The decision to end the test may also be taken by the supervising doctor if there are significant ECG changes of if it is felt that the sufficient level of exercise has been achieved.

As soon as the treadmill is stopped, you need to quickly get off the treadmill, return to the exam table and lie on your left side so that the repeat echocardiogram can be performed. Since the treadmill is stopped suddenly, it is normal to feel a little unsteady when getting off the treadmill and onto the exam table for the echo; you need not worry about these.

Your heart rate, blood pressure and ECG will continue to be monitored after stopping the exercise, until these parameters return to normal.

What is contrast stress echocardiography?

Dobutamine stress echocardiography

It is also a form of stress echocardiography, performed when the patient is unable to exercise. In this test, instead of exercise, a medication known as dobutamine is administered through an intravenous drip to speed up the heart beating to produce stress on the heart. In some patients in whom dobutamine alone is unable to speed up the heart beating as desired, another medication known as atropine may also have to be injected. Rest of the procedure is nearly same as exercise stress echocardiography.

Although exercise stress echocardiography is generally preferred over dobutamine stress echocardiography in patients who can exercise, there are certain cardiac conditions in which the latter is preferred. Your doctor should be able to choose the most appropriate test for you.

Acknowledgement