14 Syncope


14 Syncope

14.1 Basics


Syncope is the sudden, temporary loss of consciousness as a result of cerebral hypoperfusion associated with loss of muscular tone. Recovery is spontaneous. Unconsciousness usually lasts 30 to 60 seconds and up to 5 minutes at most.

There is no loss of consciousness in presyncope. Depending on the cause and duration, syncope may also be followed by cerebral seizures.


Around 15% of all children suffer at least one syncope episode in their life. The peak frequency is during adolescence. Syncope is rare in preschool children.


Syncope is most frequently (70%–80%) mediated neurally in children and adolescents. The term vasovagal syncope was previously used and the term neurocardiogenic syncope is sometimes used synonymously. Today, these types of syncope are described as vasodepressor, cardioinhibitory, or mixed, depending on the reaction pattern.

The most important causes and differential diagnoses of syncope are listed in Table 14.1 and Table 14.2.

Table 14.1 Causes of syncope

Neurally mediated syncope

  • Reflex syncope (vasodepressor, cardioinhibitory, mixed)

  • Postural tachycardia syndrome

  • Dysautonomia (e.g., associated with neuropathies)

  • Situational syncope (triggered by coughing, sneezing, pressing the carotid sinus, passing stools, pain)

Cardiac syncope

  • Arrhythmias:

    • Tachycardias: supraventricular tachycardia, atrial flutter/fibrillation, ventricular tachycardia, ventricular flutter/fibrillation (underlying diseases: long QT syndrome, short QT syndrome, Brugada syndrome, right ventricular dysplasia, myocarditis, catecholamine-induced ventricular tachycardia, right ventricular outflow tract tachycardia)

    • Bradycardias: sinus bradycardia, sinus node dysfunction, AV block, pacemaker malfunction

    • Asystole

  • Cardiac obstructions:

    • Outflow tract obstructions: aortic stenosis, hypertrophic obstructive cardiomyopathy

    • Inflow tract obstructions: mitral stenosis, pericardial tamponade, constrictive pericarditis

  • Myocardial dysfunction: dilative cardiomyopathy, hypertrophic cardiomyopathy, anomalous coronary arteries, myocardial ischemia

  • Cyanotic spells associated with cyanotic defects (esp. tetralogy of Fallot)

  • Pulmonary hypertension

  • Mitral valve prolapse syndrome (very rare)

Table 14.2 Differential diagnoses of syncope

Neurological diseases

  • Seizure

  • Migraine (“confusional migraine”)

  • Intracranial pressure, tumors

  • Cerebral hemorrhage, ischemia

  • Encephalitis

Psychiatric disorders

  • Panic attacks

  • Conversion syndromes

  • Hyperventilation

  • Breath-holding spell

Metabolic diseases

  • Hypoglycemia

  • Electrolyte imbalances (incl. diabetes insipidus, inadequate ADH [antidiuretic hormone] secretion syndrome, adrenal insufficiency)

  • Anorexia nervosa

  • Toxins

  • Anemia

The differential diagnoses listed in Table 14.2 must be distinguished from syncope. Breath-holding spells are frequent among toddlers, who may stop breathing until losing consciousness due to anger, fear, etc. Seizures, which should not be interpreted to be syncope, are also among the most frequent differential diagnoses.

14.2 Diagnostic Measures

Medical history

The medical history is an important component of diagnosing syncope. In combination with the physical examination, it allows a majority of syncopes to be distinguished from differential diagnoses. The following points should be included in the medical history (Table 14.3):

Table 14.3 Frequent causes and differential diagnoses of syncope and indicative findings in the history


Indicative findings in the history

Neurally mediated syncope

  • Prolonged standing

  • Prodromal stage (dizziness, sweating, spots before the eyes, nausea)

  • Loss of muscle tone, collapsing; convulsions are rare, but possible

  • Length of unconsciousness 0.5–5 min

Breath-holding spell

  • Early childhood (toddlers)

  • Trigger: scare, anger, or fear

  • Often a short scream followed by apnea

  • Possible loss of consciousness, sometimes seizure

Cardiac syncope

  • Sudden loss of consciousness without prodromes

  • Syncope during or shortly after physical exertion

  • Rapid heartbeat, chest pain

  • Positive family history of sudden cardiac death

Long QT syndrome (LQTS)

  • LQTS 1: triggers are physical exertion, swimming

  • LQTS 2: triggers are acoustic signals, emotional stress

  • LQTS 3: triggers are resting, sleep

  • Jervell–Lange–Nielsen syndrome: inner ear hearing loss

  • Anderson or Timothy syndrome: musculoskeletal anomalies


  • Headache

  • Impaired vision

  • Nausea

  • Sometimes aura or confusion


  • Duration of unconsciousness usually longer than in neurally mediated syncope

  • Passing stool or urination

  • Biting the tongue

  • Postictal fatigue

  • Typical age of manifestation for various forms of epilepsy

  • Personal history:

    • Number and timing of the previous syncope episodes

    • Previous diseases (especially cardiac disease, epilepsy, migraines, diabetes mellitus, thyroid disease)

    • Possible pregnancy?

    • Medication history

    • Alcohol/drug consumption

    • Sleep habits

    • Fatigue, exhaustion, weight loss

    • Eating and drinking habits

    • Sports

  • Family history:

    • Sudden deaths before age 30 years

    • Congenital heart defects or arrhythmias

    • Epilepsy or migraines

    • Syncope

  • Situation before syncope:

    • Body position (sitting, lying, standing)

    • Physical exertion

    • Fear or scare, unexpected sound

    • Urination, bowel movement, coughing, pressing, swallowing

    • Turning the head, narrow collar

    • Meal

    • Full, overheated room

    • Menstruation

  • Onset of the syncope:

    • Nausea, vomiting

    • Sweating

    • Dizziness

    • Blurred/double vision

    • Impaired speech

    • Impaired hearing

    • Palpitations, rapid heartbeat

    • Pain in the face or neck

    • Aura

    • Slumping, collapsing, falling down

  • Description of the syncope:

    • Duration of unconsciousness

    • Skin color: pallor, cyanosis, flushed

    • Breathing: apnea, hyperventilation, stridor, snoring

    • Muscle tone: lax, heightened

    • Movements: myoclonic spasms, tonic–clonic movements, asymmetry

    • Gaze deviation

    • Biting the tongue, salivation, automatisms

  • After the syncope:

Jun 13, 2020 | Posted by in CARDIOLOGY | Comments Off on 14 Syncope

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