The word syncope is of Greek origin and originally referred to the intentional omission of a sound or word in speech or writing in order to omit it. In medicine, it was first described in French in the 14th century and refers to a sudden, brief loss of consciousness. It is as if the patient’s sensory, perceptual, thinking, speech, and other conscious activities are omitted for a brief period of time. Syncope is a clinical syndrome also known as fainting. The syncope is caused by a sudden decrease in whole brain blood flow and a temporary lack of blood or oxygen supply to the brain, resulting in a loss of consciousness due to inhibition of reticular function; it lasts from a few seconds to a few minutes; it cannot maintain postural tension during the attack, so it cannot stand and faint; however, recovery is quick.
The main performance of a typical syncopal episode can be divided into 3 phases.
(1) Prodromal phase: Autonomic symptoms are obvious, sudden pallor, cold sweat, nausea, fatigue, dizziness, tinnitus, and body swaying due to hypotonia.
(2) Syncope phase: loss of consciousness and generalized loss of muscle tone and collapse.
(3) Recovery period: The patient gradually wakes up, still pale, sweating, and weak. There may be nausea and hyperventilation, but no confusion and headache.
Clinical types
(1) Hypotensive syncope: Hypotension can be caused by dysfunction of the reflex arc that regulates blood pressure and heart rate.
(1) Reflex syncope: In recent years, it is also known as neuralmediated syncope. It includes several types with approximately the same pathogenesis.
A. Vascular decompression syncope (vasodepressorsyncope): also known as vasovagalsyncope or simple syncope, is the most common type in clinical practice. It can develop in men and women of any age. Twenty to 25 percent of young people suffer from this syndrome, and it is more common in younger, weaker women. The onset of the disease has obvious triggers, commonly pain, fear, seeing blood, receiving an injection or minor surgery, hot weather, crowded places, hunger, fatigue, etc. Most of the episodes occur in the standing position, occasionally in the sitting position, and never in the lying position.
Most patients have only occasional episodes, a few have a family history of syncope, and their blood pressure is in the normal range or low normal.
B. Urinary syncope (micturitionsyncope): Patients are almost all male, most middle-aged patients, syncope occurs in standing urination or just after urination, often at night, in the morning or when waking up from nap to urinate, mostly without prodromal symptoms and sudden syncope, the recovery period is less symptomatic. After drinking alcohol, cold weather, and fatigue are possible triggers. In addition to the dysfunction of the reflex arc that regulates blood pressure and heart rate, it is also associated with the increase in intrathoracic pressure due to breath-holding during urination, the lack of blood supply to the brain due to getting up after a long sleep, and the high vagal tone and low blood pressure at night, etc. Some people classify it as multifactorial syncope. Defecationsyncope is rare and its mechanism is similar to that of urinary syncope.
C. Cough syncope (tussivesyncope): Loss of consciousness and hypotonia immediately after a violent cough, which is brief. Few patients feel dizzy and dizzy first, and their faces change from blue to pale and sweating. Patients are mostly obese men after middle age, frequent smokers with bronchitis and emphysema, and children with pertussis or asthma. Most of them follow repeated coughing, and occasionally fainting is seen immediately after a single cough, call, sneeze, yawn, or laughing. Coughing increases intrathoracic pressure, resulting in obstruction of venous return and cardiovascular reflex factors play a role in the onset.
D. Swallowingsyncope: It occurs in patients with pharyngeal, laryngeal, esophageal, or mediastinal diseases and/or atrioventricular block, sinus syndrome, bradycardia, or myocardial infarction after swallowing cold, hard, sour, or spicy foods or gas-producing beverages, without significant discomfort before or after the attack, and is not related to body position. The pathogenesis is related to mechanical stimulation of the upper gastrointestinal tract, abnormal afferent impulses triggering reflex cardiovascular inhibition, and abnormal sensitivity of the cardiac conduction system to vagal excitation.
E. Syncope caused by glossopharyngeal neuralgia or other visceral diseases: this type of syncope is rare. Transient syncope occurs during lingual-pharyngeal neuralgia, biliary colic, renal colic, bronchial or gastrointestinal endoscopy. It is associated with severe pain and hyperreflexive response of visceral receptors.
F. Carotidsinussyncope: Also known as hypersensitive carotidsinus. It is a common cause of syncope in men over middle age. Patients often have carotid atherosclerosis, or carotid aneurysm, inflammation of the carotid sinus, or compression by adjacent tumors or enlarged lymph nodes, mediastinal tumors, etc. The onset of syncope is triggered by excessive neck turning, head bowing, head tilting, or high and tight collars.
②Upright hypotensive syncope: It refers to the syncope that occurs when the patient’s blood pressure drops significantly when the patient changes from prone or squatting to upright soon. When a normal person suddenly stands up from a recumbent position or a long squat, a large amount of blood (300-800ml) is rapidly transferred to the lower extremities, resulting in a sudden decrease in centripetal blood volume and a drop in blood pressure, but the signal can be transmitted through the carotid sinus and aortic arch pressure receptors, resulting in reduced inhibition of the vasomotor center and increased tension of the sympathetic-adrenergic system, as well as the participation of the renin-angiotensin-aldosterone system, resulting in small artery contraction and heart rate is accelerated, maintaining adequate cardiac output, and the blood supply to the brain is not affected.
(2) Cardiogenic syncope.
(1) Arrhythmias: complete atrioventricular block, especially in the presence of A-S syndrome, pathological sinus node syndrome, ventricular or supraventricular paroxysmal tachycardia, atrial fibrillation; and the use of drugs such as quinidine, digitalis, antimony potassium tartrate, etc.; bradycardia (less than 35-40 beats/min), tachycardia (higher than 150 beats/min), sudden decrease in cardiac output per beat or interruption, resulting in syncope due to whole brain ischemia.
②Coronary heart disease and myocardial infarction: coronary heart disease can cause syncope due to ventricular arrhythmia caused by acute myocardial ischemia.
(3) Heart disease causing reduced cardiac output: In addition to coronary artery disease and myocardial infarction, congenital heart disease, especially tetralogy of Fallot.
(3) Cerebrovascular syncope.
(1) Transient cerebral ischemic attack of carotid or vertebral artery, with focal symptoms in the vascular supply area, occasionally combined with syncope, and all symptoms subside within 24h.
Syncope occurs in 1/3 to 2/3 of patients with polyarteritis major, and it develops during activity, and all major vessels are not palpable.
In subclavian artery steal syndrome, loss of consciousness is triggered by upper extremity activity, the radial artery pulsation on the affected side is weakened or absent, and blood pressure is more than 2.66 kPa (20 mmHg) lower than that on the opposite side.
(4) Basilar artery type migraine is mostly seen in young women, often with a positive family history of vertigo followed by headache. Syncope mostly occurs before headache, and loss of consciousness occurs gradually with several hours of blurred consciousness, and cerebral vasospasm is thought to be the cause of syncope.
(4) Multifactorial syncope and other syncope.
(1) Syncope caused by hyperventilation: mostly hysterical, occurs after stimulation, respiratory enhancement and hyperventilation increase carbon dioxide excretion and produce respiratory alkalosis, causing pulmonary capillary constriction leading to cerebral ischemia, alkalosis also causes a decrease in free calcium in the blood, these changes cause the patient to become dizzy, dizzy, dry mouth, facial and limb tingling, hand and foot twitching, tightening sensation in the chest, panic, and may gradually lose consciousness, heartbeat The patient may gradually lose consciousness and have a rapid heartbeat, but the blood pressure is normal. Reassurance and suggestion can be effective, and slow intravenous injection of calcium gluconate 10ml can relieve hand and foot convulsions.
②Crying syncope: also known as breath-holdingspells, commonly known as “gas death disease”, seen in 1 to 4 years old children. The onset is often due to pain, scolding or fright. The child cries out and then holds his breath, turns blue, loses consciousness, and wakes up quickly after a few seconds or a dozen seconds of breathing. It is easy to be misdiagnosed as epilepsy and will not occur after 3-4 years of age.
(3) Supine hypotension syndrome: seen in pregnant women in late pregnancy and huge tumors in the abdominal cavity, with onset when the patient is in supine position, showing sudden drop in blood pressure, accelerated heart rate, vertigo and even syncope. This is due to the enlarged uterus or tumor compressing the inferior vena cava, which causes a sudden decrease in the amount of blood returned to the heart. The symptoms can be relieved when changing the position to sitting or right side lying.