Postural Hypotension is a condition where there are episodes of low blood pressure when a person stands up or sits down. A person feels dizziness and lightheadedness when sitting up or standing quickly. This indicates that the cardiovascular system does not make quick adjustments to accommodate changed position. This situation is possible in people who are on certain medications. For persons who constantly face low blood pressure, this is not an alarming situation.
Diuretics, drugs for hypertension, heart medications and antidepressants can lead to postural hypotension. Hypothyroidism, hyperthyroidism or other endocrine disorders can result in episodes of postural hypotension. Severe blood loss can cause sharp sharp fall in blood pressure. Other causes for postural hypotension are dehydration, diabetes and varicose veins.
ECG and EKG can check for any possible irregularities in the heart rhythm. The doctor might conduct a tilt-table test to check your body reaction to differences in position. Blood tests help detect any anemia or hypoglycemia. Persons suffering postural hypotension can increase salt intake slightly. Drinking plenty of water aids in increasing blood volume and preventing dehydration.
Tilt table test
Tilt table test is a diagnostic test that is conduced on patients suffering from symptoms such as sudden drop in blood pressure. Patients suffering from symptoms such as fainting spells or severe lightheadedness may be asked to go through the tilt table test to check changes in postural hypotension. The tilt table test can throw light on unexplained fainting spells. During a tilt table test, the blood pressure is monitored with respect to its response to stress of gravity. Syncope is caused by unusual body response to position changes. Patients undergoing tilt table test are connected to ECG-type machine and IV line too. Isoproterenol or similar drugs are used during the tilt table test. It is essential that the physician is informed of any medications such as appetite suppressants and sleeping pills. The patient is monitored in supine position and later in sitting position. Any symptoms of dizziness or vertigo are noted. Abnormal results of tilt table test are indicative of abnormality of blood pressure regulation.
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.
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Bibliography / Reference
Collection of Pages - Last revised Date: April 23, 2019