What Is Postural Orthostatic Tachycardia Syndrome?

Normal responses during tilt tests include
(1) Increased heart rate by about 10-15 beats / min
(2) Diastolic blood pressure increased by 10mmHg, and systolic blood pressure remained unchanged. When the normal human body changes from the supine position to the upright position, about 300-800ral of blood is transferred from the chest cavity to the lower limbs, causing an increase in venous volume, reducing preventricular load, reducing cardiac output, decreasing arterial pressure, and aortic arch and cervical sinus baroreceptor tension Weakened, the vagus nerve afferent tension disappeared, and the sympathetic nerve outgoing signal increased, compensating to increase cardiac output by accelerating heart rate and peripheral vasoconstriction. Therefore, the normal physiological response is a slight increase in heart rate, a slight decrease in systolic blood pressure, an increase in diastolic blood pressure, and constant mean arterial pressure.

The upright tilt test is an auxiliary examination method used to check whether the veins are normal. In patients with vasovagal syncope, when the supine position is changed to the inclined position, the degree of blood flow stasis in the veins of the lower part of the body is more significant than that of healthy people. The amount of blood returned to the heart suddenly decreases, the left ventricle contracts strongly, and the lower left ventricle is stimulated. The mechanoreceptor C fiber, which has a strong impulse, is transmitted to the brain stem. The reflex causes a decrease in sympathetic nerve activity and hyperstimulation of the vagus nerve, which leads to slow heart rate and peripheral vasodilation, reduced cardiac output, decreased blood pressure, and syncope. Through this examination, the corresponding symptoms can be judged.

Name: Upright tilt test

category: Special inspection

Normal upright tilt test

Clinical significance of upright tilt test

The abnormal reactions are as follows:
(1) Orthostatic tachycardia syndrome (POTS): increased heart rate> 30 beats / min or pulse duration of 120 beats / min, mostly complaining of palpitations, fatigue, and signs of syncope.
(2) Hypotension in an upright position: a reduction in systolic blood pressure of at least 20 mmHg or a diastolic blood pressure of at least 10 mmHg.
(3) Vasovagal syncope: It usually manifests as a sudden drop in blood pressure with symptoms. It usually occurs more than 10 minutes after the start of the tilt test, often accompanied by bradycardia. The blood pressure drop and the heart rate decrease may not be completely parallel. The person with the heart rate reduction as the prominent manifestation is the cardio-inhibitory type, the person with the blood pressure reduction as the prominent manifestation, the heart rate is mildly slowed as the vascular inhibition type, and the heart rate and blood pressure are significantly decreased as mixed type.
(4) Autonomic dysfunction: The systolic and diastolic blood pressure are immediately and continuously reduced without a significant increase in heart rate, leading to loss of consciousness, often accompanied by hyperhidrosis, constipation, and fear of autonomic dysfunction.
(5) Psychological response: Symptoms without corresponding changes in heart rate and blood pressure.
(6) Cerebral syncope: Cerebrovascular ultrasonography in the tilt test showed cerebral vasoconstriction without hypotension or bradycardia. People to be checked: those with abnormal blood vessels, used to evaluate syncope.

Precautions for upright tilt test

Unsuitable people:
(1) Cardio-cerebral vascular disease: syncope caused by aortic stenosis or left ventricular outflow tract stenosis, severe mitral valve stenosis with syncope, patients with syncope who have known severe stenosis of the proximal coronary artery, Patients with syncope
(2) pregnancy
(3) Patient refuses
Contraindications before the test: fast for 4 hours before the test and prepare with a defibrillator and rescue medication.
Requirements during the test: If this is the first trial, the cardiovascular active drug must be stopped for more than 5 half-lives, and normal saline is infused before the test. In order to evaluate the efficacy of the drug, it should be inserted at the same time when repeating the test to reduce the error caused by the diurnal changes of the autonomic nerve, and to keep the other test conditions such as the dose and duration of the drug consistent. During the test, the heart rate and blood pressure should be continuously monitored and recorded.

Upright tilt test inspection process

The subject lies supine on a sloping bed, supine for 10 minutes in a quiet state, connected to the blood pressure ECG monitor, opened the venous channel, and massaged the left carotid sinus for 5-10 seconds under monitoring (patients over 60 years old do not do this test), If there is no manifestation of carotid sinus allergy, after the routine measurement of blood pressure and heart rate, tilt the bed to 60-80 degrees for 3-5 seconds for 25-45 minutes, and measure blood pressure and heart rate every 3-5 minutes.