In syncope (synonyms: General collapse; Blackout; Gowers syndrome; Cardiac syncope; Cardiac syncope; Collapse; Short-term loss of consciousness; Fainting; Fainting syndrome; Sympathicovasal seizure; Syncopal seizure; Syncope; Syncope with vasoconstriction; Vagus-induced fainting; Vagus-induced fainting; Vasomotor instability; Vasomotor phenomenon; vasovagal syncope; vasovagal seizure; vasovagal reflex; vasovagal phenomenon; vasovagal syndrome; ICD-10 R55) is a brief loss of consciousness (“transient loss of consciousness”, TLoC) caused by reduced perfusion of the brain and usually accompanied by a loss of muscle tone. A decrease in systemic blood pressure < 60 mm Hg lasting for about 6-8 seconds is already sufficient for syncope, i.e., an attack-like loss of consciousness, to occur. According to the S1 guideline, presyncope is defined as follows: “Prodromal stage (precursor symptoms) of syncope with diminishing of the senses (black vision, silent hearing), possibly with sweating and pronounced hyperventilation (increased breathing that exceeds demand). Does not have to progress to syncope.” Transient loss of consciousness (“TLoC”) is defined as follows according to the European Society of Cardiology (ESC) guideline [Guidelines: 4]:
- Short duration (<5 min)
- Abnormal motor control
- Passager lack of response to address or stimuli
- Amnesia (failure of memory) for the duration of unconsciousness
In syncope, the following forms can be distinguished:
- Orthostatic syncope (about 27%) – syncope during the change from a lying, sitting or kneeling to an upright position.
- Cardiogenic syncope/cardiac syncope (approximately 12%) – syncope affecting the heart.
- Rhythmogenic syncope (syncope caused by cardiac arrhythmia).
- vasovagal syncope (VVS; synonym: reflex syncope): eg.
- Orthostatic vasovagal syncope; trigger: long, quiet standing; also often confined or stuffy spaces.
- Syncope in hypersensitive carotid sinus; trigger: pressure on carotid sinus.
- Blood/injury associated vagal syncope; triggers: injury, seeing blood, sudden pain
- Syncope associated with certain irritations; triggers: e.g. swallowing, micturition (urination).
- Syncope due to a Valsalva maneuver (about 10%; forced expiration (breathing out) against the closed mouth and nasal opening while using the abdominal press).
- Neurogenic syncope (about 5%) – syncope affecting the nervous system.
- Metabolic syncope (about 3%) – syncope due to a metabolic disorder.
- Psychovegetative syncope (about 1%).
- Unclear syncope (about 42%)
The ESC guidelines recognize three categories of syncope [5, Guidelines: 2]:
- Reflex syncope (vasovagal syncope) – short-lasting loss of consciousness due to excessive vagal tone; there are many causes:
- Emotionally induced syncope (experiences of shock or pain: mainly due to blood/injury associations).
- Neurocardiogenic syncope (physical stress situations: e.g., after prolonged standing).
- Carotid syncope (due to massage on the carotid sinus).
- Visceral reflexes (visceral syncope) in the context of defecation (defecation), micturition (emptying of the bladder; micturition syncope) or swallowing (visceral reflex syncope)
- Syncope without recognizable triggers
- Syncope due to orthostatic hypotension (abnormal drop in blood pressure on rising) (synonyms: orthostatic dysregulation; orthostatic hypotension, orthostatic circulatory dysregulation).
- Cardiac syncope – cardiac-related syncope.
- Rhythmogenic syncope – brief loss of consciousness due to cardiac arrhythmia.
- Bradycardic arrhythmias: Sick sinus syndrome, 2nd and 3rd degree AV blockages.
- Tachycardic arrhythmias: supraventricular tachycardias, ventricular tachycardias/ventricular fibrillation (e.g., after myocardial infarction, ion channel diseases such as Brugada syndrome or long QT syndrome [Romano-Ward syndrome])
- Mechanical causes (cardiovascular syncope): e.g., symptomatic aortic valve stenosis.
- Rhythmogenic syncope – brief loss of consciousness due to cardiac arrhythmia.
Syncope can be a symptom of many diseases (see under “Differential diagnoses”).In the meantime, a gene on chromosome 2q32.1 has been identified as another cause: Carriers of this gene have an increased risk of fainting suddenly and unexpectedly, from which they usually awaken a short time later. Homozygous carriers of this variant had a 30% increased risk of syncope during their lifetime. Sex ratio: In childhood, girls are more frequently affected than boys. Frequency peak: The symptom occurs particularly in the elderly, but children, especially between 12 and 19 years of age, may also be affected by syncope. Thus, approximately 15% of all children experience syncope at least once by adulthood. Adolescents have cardiac (“heart-related”) syncope only in exceptional cases, and their proportion increases markedly at the latest from age > 65 years. Approximately 3-5% of patients in an emergency department present with the leading symptom “syncope”. The prevalence (disease frequency) is 6% of all elderly people (in Germany). Neurogenic syncope is most common, followed by circulatory syncope and syncope caused by cardiac arrhythmias. Adolescents have cardiac syncope only in exceptional cases, and its proportion increases markedly at the latest at an age > 65 years. Course and prognosis: Onset is usually sudden and is characterized by spontaneous (by itself) and complete recovery. The following questions must be answered immediately: is it syncope (see above) or are other serious disorders underlying the short-term unconsciousness? Is there a life-threatening event? Are there any consequences of the fall that require treatment? Note: Assessment of syncope should begin immediately in an emergency department. The goal is to determine as quickly as possible whether there is a low or high risk for cardiogenic (heart-related) and therefore potentially life-threatening syncope (recommendation grade I) [current ESC guidelines].Arrhythmias (cardiac arrhythmias) usually occur shortly after fainting. In low-risk patients (CSRS, Canadian Syncope Risk Score), half of the serious arrhythmias became apparent within the first 2 hours of admission to the emergency department; in moderate- and high-risk patients, within 6 hours; 3.7% of patients with syncope are arrhythmic within 1 month of syncope. Also, as an emergency aboard airliners, syncope (35%), followed by angina pectoris (“chest tightness”; sudden onset of pain in the heart area)/thoracic pain (chest pain) (11.9%), and cardiac discomfort (23%) represent the most common emergency. The incidence rate (frequency of new cases) of being involved in a traffic accident involving a passenger vehicle, truck, or motorcycle after syncope and thus receiving medical attention was 20.6 per 1,000 person-years (PY), almost double the rate of 12.1/1,000 PY in the general population. In patients with syncope who had no known cardiovascular disorders, syncope of unclear cause increased the incidence of atrial fibrillation (AF) by 84%, future coronary events by 85%, aortic valve stenosis (narrowing of the outflow tract of the left ventricle) 106%, and heart failure (heart failure) 124%. Mortality (number of deaths in a given period, relative to the number of the population in question) was 22% higher and cardiovascular mortality 72% higher. Syncope due to orthostatic hypotension (abnormal drop in blood pressure when sitting up) increased the incidence of heart failure (heart failure) by 78%, atrial fibrillation (AF) by 89%, and all-cause mortality by 14%. The risk of suffering an apoplexy (stroke) increased by 66%. Symptomatic high-risk patients require prompt further diagnosis and should subsequently be treated as inpatients.Asymptomatic high-risk patients can be discharged promptly and followed up as outpatients if low-risk syncope is unclear. For the definition of asymptomatic high-risk patients, see “Further Therapy.”
