Syncope is a sudden onset of transient loss of consciousness accompanied by a decrease or loss of muscle tone that lasts from a few seconds to a few minutes and recovers on its own, and is essentially a temporary decrease in cerebral blood flow. Vaso-vagal syncope is a syndrome in which various stimuli mediate reflexes via the vagus nerve, resulting in dilatation of small visceral and muscular vessels and bradycardia, manifested as arterial hypotension with transient loss of consciousness, which recovers spontaneously without neurological localization signs. Vasovagal syncope is one of the more common causes of syncope in childhood.
I. Clinical characteristics
1. The onset of syncope in school-age children is more frequent in girls than in boys.
2. There may be aura before the onset of syncope, such as transient dizziness, inattention, pallor, visual and auditory loss, nausea, vomiting, sweating, unsteadiness, etc.
3. Syncope usually occurs suddenly when rising from a standing or sitting position.
4. At the beginning of the attack, the heart rate is often accelerated and the blood pressure can be maintained, but later the heart rate slows down and the blood pressure gradually decreases.
5. After the attack, there may be weakness, dizziness and other discomfort, and in severe cases, there may be forgetfulness, trance, headache and other symptoms, which last 1-2 days and disappear.
6.Signs such as decreased blood pressure, slow heartbeat and dilated pupils are seen during the attack. There are often no positive signs during the interictal period.
7. High temperature, poor ventilation, exertion and various chronic diseases can trigger it.
Diagnosis basis
1.With the above clinical characteristics
2. Positive upright tilt test. The upright tilt test is a new test method developed in recent years, which plays a decisive role in the diagnosis of vasovagal syncope.
(1) upright tilt test methods There are three commonly used ones.
a. Basic tilt test: stop using all drugs affecting vegetative nerve function 3 days before the test, and fast 12 hours before the test. The child is placed supine for 5 minutes, arterial blood pressure, heart rate and II-lead electrocardiogram are recorded, and then the child stands on a tilt-slab bed (tilt angle of 60 degrees or more) until a positive reaction occurs or the full 45 minutes is completed. During the test, blood pressure, heart rate and lead II ECG were measured every 5 minutes immediately from the beginning of the test, and the child could be monitored at any time if he/she had symptoms of discomfort. Terminate the experiment immediately for children with positive reactions and place the child in the supine position until the positive reaction disappears, and prepare emergency medication.
b. Multi-stage isoprenaline tilt test: The preparation and monitoring indexes before the experiment are the same as those of the basic tilt test, and the experiment is carried out in 3 stages. Each stage first lying flat for 5 minutes, drug injection (isoprenaline), and then tilted to 60 degrees after the drug effect is stabilized, for 10 minutes or until a positive reaction. If the previous stage was negative, the concentration of isoprenaline was increased sequentially in the order of 0.02-0.04μg/kg.min, 0.05-0.06μg/kg.min and 0.07-0.10μg/kg.min .
c. Single-stage isoprenaline tilt test: The experimental method is the same as that of the multi-stage isoprenaline tilt test, but only from the third stage.
(2) upright tilt test positive results are judged by the following criteria: the child in the process of tilt syncope or syncope aura (dizziness and often accompanied by one or more of the following symptoms: visual and auditory loss, nausea, vomiting, sweating, unstable standing, etc.) accompanied by one of the following conditions: j. diastolic blood pressure <6.7kpa and/or systolic blood pressure <10.7kpa or mean pressure drop of 25% k. Sinus bradycardia (heart rate <75 beats/min at age 4-6 years; heart rate <65 beats/min at age 6-8 years; heart rate <60 beats/min or sinus arrest >3 seconds at age 8 years or older; l. Transient atrioventricular block of degree II or higher; m. Junctional rhythm (including escape heart rate and accelerated voluntary heart rate).
Response types: According to the changes of blood pressure and heart rate during the test, the positive responses were classified into the following three types: 1) cardiac depression response, with a steep drop in heart rate as an indication, showing bradycardia and no drop in systolic blood pressure; 2) vasopressor response, with a significant drop in blood pressure and an increase in heart rate; 3) mixed response, with a significant drop in both blood pressure and heart rate.
Differential diagnosis
1. Cardiogenic syncope: It is caused by a sudden decrease in cardiac output due to organic heart disease, and is mostly seen in severe aortic or pulmonary valve stenosis, atrial mucus aneurysm, acute heart attack, severe arrhythmia, Q-T interval prolongation syndrome, etc. It can be differentiated by electrocardiogram and echocardiogram.
2, hypoglycemia: often have a history of hunger or use of hypoglycemic drugs, mainly weakness, sweating, hunger, slow onset of syncope, no change in blood pressure and heart rate during the attack, low blood glucose laboratory tests, sedation glucose quickly relieve symptoms.
3, epilepsy: do electroencephalogram to identify.
4, upright adjustment disorder: upright test (ECG), upright tilt test, etc. are feasible to differentiate.
5, also need to identify with hysterical syncope, hyperventilation syndrome, etc.
IV. Treatment
1.General treatment
(1) Avoid factors that may induce vasovagal syncope, such as overheated environment and dehydration, etc.
(2) Tell the child to sit or lie down immediately when there is a seizure.
(3) Observation treatment is available for patients who have only one or a few episodes.
2.Medication: For children with recurrent seizures without any aura symptoms before the seizure and with severe symptoms, the following drugs can be used.
(1) β-blocker Metoprolol 1-4mg/kg/d, divided into 2 oral doses, can prevent seizures.
(2) Diisoproterenol 3-6 mg/kg/d in 4 oral doses.
(3) Scopolamine Scopolamine hydrobromide 0.006 mg/kg/d in 4 oral doses.
3. For children with severe cardiac suppression type or mixed manifestations, cardiac pacing therapy may be considered.