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Heart Diagnostic Testing
Heart Diagnostic Testing
A full array of diagnostic technology
Regional’s physicians draw on imaging devices that can "see" the form and function of the heart giving physicians a comprehensive diagnostic profile of the cardiovascular system to use in determining nature and severity of a patients' heart problems. These non-invasive procedures are the tests that are usually performed first when your doctor wants to document information about your heart. This information may be used later to compare the function of your heart at this time with the results of tests taken in the future.
Non-invasive procedures are also used when a comprehensive diagnostic profile is required to establish the nature and severity of heart problems. Often, a problem can be identified by even the simplest of these, the electrocardiogram, or ECG, which is used to evaluate the origin and transmission of electrical impulses that maintain the normal heartbeat.
Studies of the heart structures -- the muscle tissues and valves -- can be obtained from several types of echocardiography, which uses ultrasound to produce images of the heart in motion. Nuclear imaging is another technique used to visualize heart structure and function.
A contrast echocardiogram may be performed to obtain greater clarity and detail of the structures of your heart. A contrast agent is a liquid which enhances the "echoes" reflected back from the heart to the transducer, lessening the interferences caused by the chest wall and muscles. It is most often used when a standard echocardiogram is not able to sufficiently reveal the status and function of the heart’s left ventricle. Contrast agents also help your physician see or identify abnormal connections or blood flow between chambers of the heart. The contrast agent is injected into the bloodstream through a vein in your arm and is eliminated from the body in urine.
An echocardiogram is a test that uses sound waves to produce an image of the heart in motion. In addition to images of the heart chambers and valves, the echocardiogram also shows the size of the heart and how big the different chambers are in relation to each other, how thick the heart muscle is, and how well the heart muscle is working. The doppler portion of the ultrasound study also shows and measures the direction and speed of flow of blood through and between the chambers of the heart.
The term "echo" refers to the way the test is performed.
A transducer placed over the heart emits waves of sounds that cannot be heard but which are reflected back from the heart tissues in an echo. These echoes are then translated into visual images by the computerized video monitor. A gel is spread over the transducer to facilitate the transmission of sound waves through the skin and chest wall. Electrodes are placed on the chest to monitor the heart beat during the test. As the transducer is moved over the chest in a systematic sequence, the sound waves that bounce back are transmitted into the video monitor which creates a permanent record of the motions of your heart. You may be asked to exhale deeply and hold your breath for several seconds at different stages of the test to keep air in the lungs from interfering with the sound waves.
The types of information that your doctor can obtain from echocardiography include:
- The shape and size of the heart, the heart chambers, and valves
- How well the heart valves open and close during each contraction and relaxation of the heart chambers
- The uniformity of movement of the heart muscle during each cycle of contraction and relaxation
- The thickness of the muscular walls of the heart
- Estimate the blood pressure within the lungs indirectly
Exercise Tolerance ECG
An electrocardiogram may be used in conjunction with exercise to test the heart’s response to increases and decreases in physical activity. This is called the "exercise tolerance test" or "exercise stress test." During this testing, the same types of electrodes are placed at the same locations on the body and connected to the same type of ECG recording device as for the resting ECG. But for this test, you are usually asked to walk on a treadmill to gradually increase physical activity, or exercise, while the ECG is recorded. If you are unable to tolerate exercise, a medication may be used to simulate the effects of exercise on your heart.
The test may take about 30 minutes, and it is usually recommended that you wear comfortable clothing and shoes. You may be asked to change into an examination gown so it is easier to place the electrodes on your chest. A resting, baseline ECG is recorded before you begin exercising, and your blood pressure will also be recorded via a blood pressure cuff, which will lay in place throughout the testing. This provides both a baseline reading and continuous reading during the test.
You begin exercising at a low level of exertion and then increase the intensity of exercise until a pre-determined end is reached. For example, the healthy individual may exercise to a point of exhaustion, or "maximal" effort. An individual who is being evaluated for heart disease or whose heart treatment is being checked may exercise to any one of the following endpoints as determined by your doctor:
- Chest pain is experienced by the patient
- Abnormalities are seen on the ECG waveform
- An undesirable change in blood pressure is detected
A "target" heart rate is achieved, as you are progressing in cardiac rehabilitation or when you have no known heart disease but other factors may prevent exercising to the point of exhaustion.
It is important to tell the doctor if you experience any discomfort during the test. Symptoms that should be reported immediately include:
- Chest pain, or discomfort in the jaw, arm, or shoulder
- Shortness of breath
- Dizziness or weakness
- Leg cramps
Exercise Echo & Pharmacological Stress Echo
Like the "resting" echocardiogram," the "stress" echocardiogram uses sound waves to produce an image of your heart. However, during this procedure, information is collected before and after exercise. First, the baseline ultrasound examination is conducted while you lie on an examination table or bed. Your heart is examined using the ultrasound transducer and images are stored on videotape. An ECG is also performed at the same time.
Then you are put through increasing levels of physical exertion using a treadmill or stationary bicycle. As with any exercise test, be sure to tell your doctor if you experience any discomfort or other symptoms during the exercise. After exercise, the ultrasound examination is repeated to evaluate any changes in the efficiency of the heart muscle and valves at the higher heart rate that comes with exertion. This also enables the doctor to evaluate the adequacy of blood supply to the heart muscle from the coronary arteries, which provide the heart’s own blood supply.
Some preparation will be required before an exercise echocardiogram. Be sure to ask questions if you are uncertain about any of the following:
- You should not eat or drink anything for three hours prior to the test. This is only to reduce the potential for nausea during exercise.
- Also, your doctor may want you to stop taking certain medications for a period of time before the test -- be sure to ask your doctor about these special instructions and don’t stop taking any medications without your doctor’s instructions.
- On the day of the test wear comfortable clothing that is suitable for exercise and that will allow the ECG electrodes to be placed. Remember that a gel will be used for both the ECG and the ultrasound; so many people prefer to wear an examination gown. Also, wear comfortable shoes.
- A consent form is signed before the test begins. Be sure to ask any questions you may have.
A pharmacological stress test is a modification of a stress echocardiogram, used when a patient is unable to walk on a treadmill. It involves intravenous injection of a medication called dobutamine which simulates the effects of exercise on the heart. Pre-medication echocardiogram images are then compared to those images taken after dobutamine has been injected to see how the heart responds to the "stress".
Holter Monitor (24-hour Continuous Ambulatory ECG)
Sometimes it isn’t possible to "catch" problems with a single ECG and a special device is used to monitor the heart rhythm and rate continuously for a prescribed period of time, such as 24 hours. If you are experiencing abnormal heart rhythms, or arrhythmias, or other symptoms, the test may be used as an "event" monitor and it will be worn for a period of time that enables the problem to be "caught" on an ECG.
The procedure uses basically the same equipment as used for an ECG, but the equipment is not tethered to a stationary monitor. A special recording device called a Holter monitor, can be worn during normal activities and allows you to remain active during the testing period. This lightweight recording device can be attached to a belt or shoulder strap. The ECG is recorded continuously for the period of time your doctor wants to study.
A diary may also be required for the period of time that the monitor is worn. Be sure to correlate the time of day, the activity you are performing, such as taking medication or participating in a meeting at work, and the specific symptoms you notice happening at the time that the target “event” or symptom is happening. The ECG monitor also may have a button to push when symptoms are being experienced. These "symptoms" also should be noted carefully in a diary.
When the evaluation period is over, the electrodes and recording device can be removed and the waveforms evaluated. When a longer period of continuous monitoring is desired, a recording can be “called in” to the doctor’s office or clinic by a special "telemetry" phone attachment.
While you are wearing an ambulatory ECG monitor, certain precautions should be taken:
- If you usually sleep on your stomach, it will be recommended to sleep on your back or side while the monitoring device is in place.
- You should avoid any device or environment that might interfere with the monitor, such as electric blankets, magnets, metal detectors, and high-voltage areas.
- Showers or baths are not approved while the Holter monitor is in place, but sponge baths are. Just be careful not to get the device wet.
- Proceed with your usual activities. Remember, this test gives the best results when the doctor can evaluate your heart during your usual activities.
- Be sure to contact the doctor’s office or clinic if an electrode falls off. Also, some monitors will make a noise which should be reported as well.
Nuclear imaging is a technique used to produce an image of blood flow, or perfusion, to the heart muscle. It is important because the heart's pumping action is responsible not only for supplying blood to the body, but also to itself through a network of vessels called the coronary arteries.
The entire heart muscle must receive adequate blood flow for the heart muscle to remain healthy. A nuclear perfusion scan is performed using a substance called a "tracer", which is a small amount of radioactive material given by injection into a vein in the arm. A special scanning camera can then "trace" this substance as it travels through the circulatory system to the heart and the coronary arteries. The scan images reveal a picture of the heart muscle and deviations where blood flow may not be adequate. Most often exercise is used as a part of this test so the heart can be visualized, during and after exercise, as well as during rest. If you cannot exercise because of a medical condition, you may be given a medication to simulate the effects of exercise.
The testing sequence:
- If you smoke, your doctor will probably ask you to stop smoking for a day before the test.
- Caffeine also may be restricted for 24 hours before the test. Remember to ask if this includes such foods as chocolate as well as soft drinks containing caffeine.
- No food or drink is allowed for 4 to 6 hours before the test, except sips of water as instructed by the doctor.
- Comfortable shoes should be worn for the exercise portion of the test.
- Be sure to tell your doctor if you experience any discomfort or symptoms, especially any chest pain, or unusual sensations in your arm, shoulder, or jaw, severe shortness of breath, dizziness, or leg cramps or pain.
- Exercise will be stopped when your limit is reached. This is based on how you feel, so be sure to tell the technician when you feel you should not, or cannot, continue. At this point the tracer will be injected through a vein in your arm.
Scanning and Post-Scan:
- You will be asked to lie very still.
Tilt Table Testing
If you have had recurrent syncope (fainting spells), the tilt table test can help determine your body responses to changes in position. During the test, you lie on a table that can be moved to a nearly upright position while your symptoms, heart rate, and blood pressure are continuously monitored.
The tilt table test is designed to induce syncope under controlled conditions. The upright position during the tilt table test causes the blood to pool (collect) in the lower part of the body, especially the legs. As a result of the test, less blood returns to the heart, less blood is available for the heart to pump, and the blood pressure tends to drop. Normally, the nerves that control the function of the heart and blood vessels are able to maintain the blood pressure by increasing the heart rate and by tightening the blood vessels. In people susceptible to vasovagal syncope, these nerves do not work properly. As a result, the heart rate slows down, the blood pressure drops, and the person loses consciousness. Once the person lies flat, normal flow is restored, and he or she regains consciousness.
The tilt table test is generally safe. By design, the test may cause you to faint for a few moments. Should this happen, the table is returned quickly to a flat position and the test is stopped. Well-trained personnel are available to handle any emergency. The test takes approximately 1-1 1/2 hours.
An ultrasound procedure measures high-frequency sound waves (ultrasound waves) as they pass through the body and rebound off certain structures. The sound waves cause no discomfort as they enter the body from a hand-held transducer that a technician places on the patient’s skin. A conductive gel or lubricant jelly is placed on the skin to help the transducer conduct the waves through the skin. As the transducer is moved along the surface of the patient’s skin, ultrasound waves enter the body and bounce off the body’s internal structures. Images of tissues and organs are created from these reflections of the sound waves.
A carotid ultrasound is one example of a vascular ultrasound. During this procedure, the transducer is placed on the patient’s neck over the carotid artery. The technician slowly moves the transducer along the course of the artery. As blood cells move through the vessel, ultrasound signals are transmitted onto a graph, where they are recorded and analyzed. This type of procedure can also be conducted to evaluate other arteries and veins in the body, such as the aorta, the major vessel carrying blood away from the heart and to the lower abdomen, where it branches into the smaller arteries that supply the vessels of the lower extremities.
Transesophageal Echocardiography is a diagnostic procedure using the soundwave technology of ultrasound plus a device called a transducer to yield an image of the heart. The pill-sized transducer is actually swallowed to get it close enough to the heart through the esophagus to get a clearer picture of the heart. An anesthetic spray is used to numb your throat and a sedative is given to help you relax during the test. The transducer is "swallowed" until it is positioned inside your esophagus behind the heart. There may be a slight sensation of pressure while the catheter is passed into position, but the procedure is not usually described as painful.
Because the transducer can be placed so close to the heart, its images are clearer than a traditional echocardiogram. Most often, the technique is used for follow-up studies of potential problems identified with other diagnostic tests, including transthoracic echocardiography. But, the technique is also used in emergency situations when a rapid diagnostic evaluation is preferable to exploratory surgery. The images obtained may be used to identify or evaluate:
- Blood clots or other abnormal masses
- The degree of heart valve dysfunction or presence of infection
- Structural defects of, or between, heart chambers
- Injury to one of the "great" vessels top