Echo & Imaging: For Patients
We offer echocardiography (cardiac ultrasound) for all patients with cardiovascular disease. The tests are performed by specially trained technologists called sonographers, and in the case of the transesophageal echocardiogram, by a specially trained cardiologist. The echocardiographic images are moving images that show the heart chambers as well as blood flow in the heart; they are stored on a computer for interpretation by a specially trained cardiologist called an echocardiographer. Cardiac nurses and nurse practitioners also assist with stress echocardiograms and with transesophageal echocardiography.
Our services include:
- Transthoracic echocardiography is performed by placing a transducer on your chest wall in a variety of locations. There is no special preparation for this examination, and the only discomfort you may feel is some pressure on your chest. The examination typically lasts one hour or less and the results will be available to your physician within 48 hours. Your doctor will receive information about the function of your heart, including the cardiac chambers and the heart valves, and will gain information about the pressures in your heart.
- Three-dimensional imaging using techniques similar to those described above will be performed in some patients to gain better visualization of certain conditions.
- Contrast echocardiography may be performed if the echocardiographic images are not clear, or if your there is suspicion of a communication between the chambers of your heart. In this case, a nurse will place an intravenous line to inject the contrast. This contrast differs from X-ray contrast and may consist of saline solution or a special agent designed for use with echocardiography. History of allergy to X-ray contrast is not a contraindication to contrast echocardiography.
- Stress echocardiography may require you to exercise, or may be done with a medication that increases your heart rate and blood pressure if you are unable to exercise. If any form of stress echocardiography has been ordered, you cannot eat for four hours prior to the examination. If you are performing exercise, you should wear comfortable clothes. Even if you are performing exercise, you may have an intravenous catheter placed to improve the imaging of your heart or to gain additional information about heart function.
- Treadmill echocardiography is usually done to evaluate chest pain to see if you have coronary artery disease with blockage in the arteries supplying your heart with blood.
- Supine bicycle echocardiography is performed if you have high pressures in your lungs or if you have valvular or congenital heart disease. This form of testing gives your doctor information about the changes that occur with exercise due to your heart problem.
- Dobutamine stress echocardiography is done in patients who are unable to exercise. Dobutamine is given intravenously, starting at low doses and increasing the dose every 3 minutes. Heart rate and blood pressure increase with each dose, and the heart is examined with ultrasound to see the effect of this form of stress on your heart. You are monitored with an electrocardiogram continuously to make sure abnormal heart rhythms do not occur.
- Transesophageal echocardiography is a test which uses a special scope fitted with an ultrasound transducer that is placed in the esophagus after numbing the back of throat with lidocaine and sedating you with medications. You must fast for a minimum of six hours before coming to the laboratory, and someone must be with you to accompany you home. You cannot drive after receiving the sedation. There are many reasons to perform this test, but the most common ones are to investigate possible infection of the heart valves (endocarditis), to evaluate a defect in the wall between the upper chambers of the heart (atrial septal defect), to investigate a possible reason for a stroke in younger patients, and to evaluate heart valves, both artificial and native valves.
Cardiac MRI and CT are used to evaluate patients who have suspected or known problems with their heart or blood vessels. MRI and CT are used in different ways, and which one is appropriate will depend upon the reason for the examination. Some specifics about each of these techniques are listed below:
- Cardiac MRI uses a strong magnet to produce images; no radiation is involved. During imaging, patients are placed within the magnet for a variable amount of time ranging from 10 minutes to one hour, during which time they remain relaxed and still. The scan is painless, although people occasionally have a slight flushing feeling in their face. The injection of intravenous contrast may be required in certain cases. This is given through a small intravenous line that is placed by one of the radiology nurses or technologists.
- Cardiac CT uses ionizing radiation to produce images. The radiation imparted by CT scans varies depending upon why the CT is being obtained. More information on CT radiation can be found at the UCSF Radiation Safety website (http://www.radiology.ucsf.edu/patient-care/patient-safety/radiation). CT scans are much quicker than MRI, and usually only takes a few minutes to perform. Intravenous contrast is required for the majority of cardiac examinations, with the exception of coronary calcium screening.
Nuclear cardiology studies use noninvasive techniques to assess the amount of blood flow to the heart muscle itself, evaluate the pumping function of the heart, and visualize the size and location of a heart attack. During a myocardial perfusion test, the technique most widely used, the images are combined with exercise (walking on a treadmill or riding a stationary bicycle) or medication-induced stress testing.. A very limited amount of an imaging agent labeled with a tiny quantity of radioactive material is injected into the blood stream during rest, and during exercise or chemical stress. A specific scanning device (gamma camera or positron emission tomograph) is used to measure the uptake by the heart of the imaging material. Healthy heart muscle tissue will absorb the radioactive “tracer.” If there is significant blockage of a coronary artery, the heart muscle may not be getting enough of a blood supply in the setting of exercise or during chemical stress. This decrease in blood flow will be detected by the images.
Myocardial perfusion studiescan thus identify areas of the heart muscle that have an inadequate blood supply, as well as the areas of heart muscle that are scarred from a heart attack. In addition to the localization of the coronary artery with atherosclerosis (hardening and narrowing of the artery due to plaque buildup), myocardial perfusion studies quantify the extent of the heart muscle with a limited blood flow and can also provide information about the pumping function of the heart.
Another important application of nuclear cardiology includes the evaluation of cardiac function with radionuclide ventriculography, in which the imaging agent is injected into the bloodstream and pictures of the four chambers of the heart are taken. In addition, nuclear cardiology techniques can be used to determine which areas of the heart muscle have been damaged by infection or heart attack, and can help cardiologists assess the nervous system of the heart when the heart muscle is damaged.