Syncope: conulsive, vasovagal, neurocardiogenic, orthostatic

Fainting (or syncope) occurs when you lose consciousness for a short period of time.

Fainting can also be called syncope.

Definition

Syncope is a loss of consciousness and posture with the characteristic consequences:

• Temporarily;
• Spontaneous recovery (on the other hand, if a patient loses consciousness and does not recover, he falls into a coma);
• Leading to the fall → the postural loss of tone leads to the fall,
• The cause is the global and transitory reduction of blood flow to the brain.

The data and information comes from the guidelines of the European Society of Cardiology (ESC) 2009, which apply in most European hospitals.

Types of Syncope

Neurogenic or reflex-mediated syncope

Pathophysiology

Reflex syncope is caused by a reflex that is generally normal, but in some people takes abnormal form in certain situations (intermittently).

The autonomic nervous system is divided into two subsystems that are interconnected:

• Sympathetic → Activated in dangerous situations and causes an increase in heart rate and blood pressure,
• Parasympathetic nervous system → Slows down the action of the sympathetic nervous system under normal conditions, slows down the heartbeat and lowers blood pressure.

An event that triggers a vavasal syncope (for example, anxiety) triggers an alarm response.

In patients with normal reflexes, activation of the vagus nerve occurs, which does not cause symptoms.

However, some people show an overreaction, which is characterized by:

1. vasodilation,
2. Bradycardia
3. Decreased blood pressure.

Classification

Reflex syncope can be classified according to their starting point:

• After the effect:
  • Cardioinhibitory → Significant reduction in heart rate and heartbeat,
  • vasodepressor → there is a vasodepressor effect, which is accompanied by a compensatory, but not sufficient increase in heart rate,
  • Mixed → The vagus nerve reacts at both levels.
• After the triggering event.
• Causes are:
  • Vasovagal syncope,
  • Situational syncope
  • Syncope due to carotid sinus syndrome,
  • Atypical forms (rare).

Vasovagal Syncope (cardio-neurogenic syncope)

Vasovagal syncope is the most common type and occurs when arterial pressure decreases, thereby reducing blood flow to the brain.

The cause can be:

• Emotional stress: (at the sight of blood, fear, pain, invasive instrumental examination procedures)
• Standing for a long time.

Long standing causes:

• An accumulation of blood in the lower extremities.
• A decrease in blood pressure at the level of the heart and baroreceptors (blood pressure receptors).

The result is the activation of the sympathetic nervous system to increase blood pressure and heart rate.

After a variable period of time during which the sympathetic nervous system is active, the vagus nerve becomes overactive and leads to bradycardia and low blood pressure, which can lead to syncope.

Situational syncope

A situational syncope is a type of vasovagal syncope that only occurs in certain situations.

A “stimulus” causes fainting, for example:

• Dehydration
• Emotional stress,
• Fear
• anxiety (for example, the fear of cannulas or blood),
• Ache
• hunger (for example, in the morning, when a person does not eat breakfast),
• After eating (in case of postprandial syncope),
• Gastrointestinal syncope (by bowel movements, by swallowing, with syncopal swallowing difficulties),
• drunkenness (alcohol abuse),
• After smoking cannabis, a feeling of loss of consciousness may occur,
• drug use,
• Induced fainting or induced hyperventilation (too fast breathing and increased oxygen uptake),
• Panic attack
• Severe cough,
• carotid sinus hypersensitivity,
• Strong pressing when urinating

Syncope due to carotid sinus syndrome,

The carotid glomus is located laterally on the neck, deeper than the sternocleidomastoid muscle, at the level of thyroid cartilage.

Normally, massaging the carotid sinus has no effect, but some people with carotid sinus syndrome or hypersensitivity respond with vagus activation such as:

• Bradycardia
• Decrease in blood pressure.

The massage must be done on both sides, first on the right, then on the left.

It must be performed lying down and standing.

The duration is 5-10 seconds.

Possible reactions can be:

• Negative – normal
• Cardioinhibitory response – the electrocardiographic pattern becomes flat (asystole). If the heart pause is longer than 3 seconds, the insertion of a pacemaker may be indicated.
• Vasodepressive reaction: decrease in systolic blood pressure by at least 50 mmHg.
• Mixed reaction.

The reaction is completely individual.

Syncope in orthostatic hypotension (OH)

It mainly affects older people.

When a person rises from sitting, pressure receptors (baroreceptors) in the carotid arteries and in the aorta detect a slight decrease in pressure.

Gravity causes the blood to drop to the legs.

The result is the stimulation of the sympathetic nervous system and thus:

• increase in heart rate,
• Provoked vasoconstriction (the blood vessels narrow).

These reactions serve to maintain arterial pressure and ensure blood circulation:

• of the brain,
• Other organs.

If this mechanism does not work, there is a drop in pressure, which can lead to syncope.

Orthostatic hypotension occurs when standing up from lying causes an arterial pressure drop (AD) of 20 mmHg.

Causes of syncopation in orthostatic hypotension

1. Functional: Side effect of drugs such as beta-blockers, MAO inhibitors, tricyclic antidepressants and nitroglycerin.
2. Structural: Includes:
   1. dysfunction of the primary autonomic nervous system, severe and typical neurological diseases also in adolescents, but which are rare, such as Shy-Drager syndrome or multisystem atrophy,
   2. Dysfunction of the secondary autonomic nervous system, more common pathologies such as diabetes.

Variants

• OH initial → Suddenly lowers arterial pressure when a person rises, but returns to normal within 30 seconds.
• OH delayed or progressive → Lowers systolic AD by at least 20 mmHg about 5-10 minutes after the person gets up.
• Dysautonomic syncope → progressive and gradual reduction of arterial pressure at Orthostase without an increase in heart rate,
• Postprandial hypotension → Lowers systolic AD by at least 20 mmHg within two hours of eating.

The difference between reflex syncope and orthostatic or dysautonomic syncope is:

1. In reflex syncope, there is an excessive function of the sympathetic nervous system, which is followed by excessive activation of the vagus,
2. With orthostatic syncopation, the sympathetic nervous system does not activate, therefore vasoconstriction and an increase in heart rate do not follow. So the pressure drops suddenly or progressively and the person has syncope with reduced blood flow to the brain.

Cardiac Syncope

Cardiac syncope is a loss of consciousness due to heart disease or disorders of the circulatory system that reduce blood flow to the brain.

Causes can be:

1. Arrhythmic: When the heart beats too weakly and does not pump enough blood to the brain. If the heart rate is elevated (for example, paroxysmal atrial fibrillation with ~140-200 beats per minute), the ventricle does not fill sufficiently and the cardiac ejection performance is too low.
2. Cardiac structure: For example, a heart attack that blocks the function of a ventricular area leads to a decrease in cardiac output. The result can be syncope.
3. Aortic stenosis hinders blood ejection from the heart and can cause syncope. If the patient rests, the cardiac output may be sufficient, but under stress it does not increase sufficiently. The result is a reduced blood flow to the brain.
4. Pulmonary embolism: Non-cardiac cause leading to occlusion of the pulmonary artery. The right part of the heart has difficulty pumping blood to the lungs and left ventricle. Syncope is caused by reduced cardiac output.

Diseases that cause cardiac syncope

• Arrhythmic
  • Bradycardia:
    • Sinus node syndrome (including bradycardic/tachycardic syndrome)
    • Changes in the atrioventricular stimulus system
  • Tachycardia
    • Sopraventricular arrhythmia
    • Ventricular arrhythmia
  • Through medications – There are medications that harm through side effects, such as bradycardia (for example, beta-blockers) or tachycardia (for example, theophylline in COPD, which can even trigger atrial fibrillation).
• Structural
  • Purely cardiac:
    • Infarct
    • dysfunction of heart valves or valve prostheses,
    • All forms of cardiomyopathy,
    • cardiac tumors,
    • pericardial diseases,
    • Congenital malformations.
  • Cardiovascular: pulmonary embolism, aortic dissection, pulmonary hypertension.

Neurological Syncope

• Often the person has an aura before a seizure (he sees or feels something abnormal).
• During a seizure, the affected person suddenly loses consciousness.
• There may be urinary and fecal incontinence.
• The person may bite his tongue.
• After the seizure, there may be confusion and drowsiness.
• Unlike a seizure, stroke can lead to muscle weakness (up to paralysis) and speech disorders.

Convulsive syncope

The person faints for at least 10 seconds and first diffuse hypertension (increase in muscle tone) and then 1-2 generalized clonic twitches (cyclic phases of contraction-relaxation of the muscles).

Syncope due to apnea

Prolonged apnea can cause syncope due to elevated C0₂concentration (carbon dioxide).

Lipothymia

Lipothymia or presyncopation is a feeling of loss of consciousness and weakness.

• Fainting or Syncope
• Normal heartbeat
• Sinus bradycardia