About the Program: Ultrasounds

Carotid Ultrasound

The carotid arteries are the two large arteries in the neck, which supply most of the blood flow to the brain. Atheromatous plaque can form in them and interfere with the flow of blood. Bits of the plaque may break off and get carried up into the arteries of the brain, where they may form a blockage, which can result in a stroke or transient ischemic attack (TIA), a mini-stroke that does not last because the blockage gets washed away. Carotid ultrasound testing is a noninvasive method for assessing how much plaque there is. A probe that emits ultrasound waves is held over the neck, and the reflected sound waves give a picture of the walls of the artery and show whether they are thickened by plaque. One of the reasons for doing the test is to see if you are a candidate for carotid artery surgery to remove the plaque (the operation is called an endarterectomy ).

Renal Ultrasound

Disease of the kidneys may either cause hypertension or be a consequence of it, and ultrasound provides a convenient and noninvasive way of looking at the kidneys and their blood supply. There are two sorts of examination. The first is a regular ultrasound test, which uses a probe held on the abdomen to measure the size of the kidneys. If one kidney is much smaller than the other, it may be that the blood flow to the shrunken kidney is obstructed, causing the high blood pressure.

The second type of test, the Duplex Doppler exam, uses a probe that focuses on the arteries going to the kidneys (the renal arteries ), measuring the rate of blood flow through them. This test is a more direct way of detecting an obstruction.

Echocardiogram

The echocardiogram is by far the best test for assessing whether the high blood pressure has had any effect on the heart. It's done using ultrasound, very high frequency sound waves that are emitted from a probe held on the skin of the chest wall and aimed at the heart. The principle is the same as that of a ship's sonar: the sound waves are reflected by the tissues of the body, and the reflected waves are picked up by the probe. By displaying these signals on a monitor like a radar screen, it's possible to measure with great accuracy the thickness of the tissues, including the heart muscle, that are reflecting the sound waves. The size of the chamber or cavity of the heart can also be calculated.

When the blood pressure is high the heart has to pump harder, and like any other muscle that's being used a lot, it enlarges. One of the things that makes the echocardiogram so useful, therefore, is that it provides a sort of cumulative measure of the height of the blood pressure over the months and years preceding the test. In patients with white coat hypertension (whose blood pressure is high only when they're in a doctor's office) the echocardiogram typically shows no signs of enlargement of the heart. But if the heart muscle is enlarged, it's usually a bad sign, because prospective studies of people who have had echocardiograms have shown that the individuals with larger hearts are at much higher risk of having a heart attack than those with normal-sized hearts. If the echocardiogram does show that your heart is enlarged, therefore, it means that your high blood pressure should be taken seriously and that you will definitely need treatment.