Adenosine Stress Test
Coronary artery disease is diagnosed by many stress tests such as echocardiography and treadmill. They determine cardiac activity with details of blood circulation and blood pressure. The stress tests are measured based on activity of the heart when subjected to exertion. The coronary arteries are examined for accumulation of plaque through triglyceride estimation and various other tests. In many scenarios the results of stress test are correlated with the laboratory analysis to identify the underlying conditions such as atherosclerosis.
Stress examinations of the heart also help in the detection of ischemia and arrhythmia. The adenosine stress test is done to identify underlying coronary artery disease. Adenosine helps in inducing the vasodilation of the coronary artery directly through the activation of the A2A receptor. The myocardial blood volume increases to a greater extent through this activity. The stenotic coronary arteries display an attenuated hyperemic response in the myocardial region of the heart. The radio tracer for the identification of coronary artery disease undergoes heterogeneous distribution. Adenosine is an endogenous nucleoside predominantly produced in the arterial vascular region. Its action is mediated through the G protein coupled adenosine receptors.
Methodology of adenosine infusion
The adenosine infusion is administered at a rate of 140 mcg/kg/min. The echocardiogram is taken by attaching twelve leads. The values of ECG are taken every minute. Along with these procedures, the blood pressure is consistently monitored for stability during the entire procedure of adenosine stress testing.
A2A receptor protein plays a significant role in the regulation of inflammatory response and immune response. A2A agonists act as effective catalysts in the identification of various diseases such as myocardial infarction and infectious diseases. These receptors help in the reduction of tissue damage.
Patient information and risk factors
The patient is advised not to consume any solid food. Water and juices are allowed prior to the procedure. The nuclear technologist injects the cardiolite and adenosine into the blood stream through an intravenous line. The cardiolite is administered to capture the cardiac images.
Water is given to patients before the start of the imaging procedure through the induced cardiolite. Adenosine is introduced through the IV line after acquiring the resting images. Anticipated side effects of adenosine are generally nausea, angina, shortness of breath and flushing. Most of these side effects are monitored by the technicians. The side effects are usually short lived. A second round of cardiolite is administered after the adenosine to acquire the second set of images. In order to reduce the side effects, patients are advised to walk on the treadmill. The entire procedure lasts for a period of two and a half hours. A comparative account is made of both sets of images at resting stage and also during stress (exercise induced). Patients are advised to take fluids preferably juices after the procedure.
The adverse effects of adenosine stress test include wheezing, hypotension with a systemic hypotension of less than 80 mm of hg, second degree heart block and cyanosis. Pregnant and lactating women are not advised to undergo adenosine stress test because of radio tracers. Incidences of hypersensitivity to adenosine have also been reported. Although adenosine stress is pharmacologically recommended for myocardial stress, one of the predominant side effects during the procedure is myocardial infarction.
Bibliography / Reference
Collection of Pages - Last revised Date: February 22, 2018