Dobutamine Stress Echocardiography
What is Dobutamine Stress Echocardiography?
Approximately 30% of patients are unable to exercise to a sufficient degree to unmask coronary artery blockages. This limitation may be due to reasons such as old age, physical deconditioning, peripheral vascular disease, arthritis, neurological disease, and concomitant illness.
In such cases, Dobutamine stress echocardiography, which is a type of stress echocardiography, is performed. Dobutamine is a medicine that increases the heart rate, heart contractility and the blood pressure, thereby mimicking the effects of exercise. It consists administering gradually increasing doses of an intravenous infusion of Dobutamine to mimic the effects of exercise. Simultaneous monitoring of the patient’s ECG, blood pressure and viewing the heart wall motion on 2D Echocardiogram and Colour Doppler is performed.
Indications for this test include establishing a diagnosis of coronary artery disease, determining myocardial viability before angioplasty or coronary artery bypass surgery, assessing prognosis after myocardial infarction or in chronic angina, and evaluating risk of surgery in patients with heart problems who are undergoing non cardiac operations. Also patients with an abnormal baseline ECG (eg: left bundle branch block (LBBB) are advised Dobutamine stress test as a routine treadmill stress test is often fallacious in this setting
What are the Pre-test instructions?
- Patient need not be fasting, but keep an interval of at least 2 hours prior to the test. Do not smoke 2 hours prior to the test.
- Avoid caffeine-containing products like coffee, tea, cold drinks, chocolate,etc.
- Bring a list of medications patient routinely takes.
- Diabetic patients who are on insulin should not take the morning insulin dose and have a light breakfast.
- Patient can take all his/ her routine medications, unless specifically instructed by doctor to stop any medications prior to the test.
- Before the test, patient will be given an explanation of the test and patient will be asked to sign a consent form and any queries will be answered.
- A relative or a friend has to accompany the patient for this test.
How is the test performed?
To perform a dobutamine stress echocardiogram the patient undergoes the resting transthoracic echocardiogram. An intravenous line is placed and the dobutamine infusion is started intravenously, first at a low dose and then the dose is increased every three minutes to increase the heart rate and overall cardiac work. At each of these stages, the heart is imaged using transthoracic echocardiography with blood pressure and ECG monitoring. Atropine is a medication that is available for use if the heart rate does not reach its predicted maximum. A contrast agent (engineered microbubble solution) is also injected during the test, to enhance the visualisation of cardiac (left ventricular) walls and assess the abnormal motion more accurately. This contrast is safe and has no major contradictions. End points include new or worsening wall-motion abnormalities, adequate heart rate response, worsening arrhythmia, moderate angina, intolerable side effects, and significant increase or decrease in blood pressure. A new or worsening wall-motion abnormality constitutes a positive test for ischemia.
During the infusion of the drug, patient can expect to feel the heart rate increasing and the force of heart contraction also increases. This occasionally causes a disconcerting sensation because the patient is lying quietly at rest while the heart feels as if it is running a race. This is to be expected during infusion of dobutamine and does not represent any harmful effect. As soon as the infusion is completed, it is discontinued and typically within five to ten minutes the heart rate and blood pressure will return to the basline levels. All of the necessary equipment and medicines to treat complications are available in the echo room.
What are the side effects and complications?
Side effects during dobutamine infusion are infrequent and include nausea, headache, tremor, anxiety, angina and arrhythmias- abnormal heart rhythms
What are the instructions after the Dobutamine Stress Test?
- Patient may resume the normal activity unless otherwise directed by the testing physician.
- Patient can drive, unless the medicine atropine was administered. Ask the doctor prior to going home.
- Take the regular medications as directed unless otherwise directed by the testing physician.
- Keep any scheduled follow-up appointments.