Syncope

Pathogenesis and cardiac alertness

Syncopal states encompass a group of episodes of brief loss of consciousness, after which the patient quickly and independently recovers with a satisfactory general condition. The main diagnostic difficulty lies in the fact that by the time of the medical examination, the attack has usually completely resolved, which often leads to an underestimation of the severity of the condition.

The most dangerous are cardiogenic syncopes, as they can precede sudden cardiac death (SCD). The reduction in cerebral blood flow in cardiac pathology occurs due to several reasons:

• Temporary cardiac arrest or a critical slowing of the heart rate (bradycardia).
• An episodic sharp drop in cardiac output occurring against the background of tachyarrhythmias.
• Mechanical obstructions to blood flow (for example, aortic valve stenosis or narrowing of the left ventricular outflow tract characteristic of hypertrophic cardiomyopathy).

Important clinical rule: any episode of loss of consciousness that occurs directly during physical exertion must primarily be regarded as a symptom of severe heart disease.

High-risk red flags

Certain characteristics of the attack require immediate in-depth evaluation as they indicate a life-threatening cause. Such situations include:

1. Onset of syncope upon changing body position (e.g., moving from a sitting to a lying position, or bending the torso forward).
2. A clear association of the episode with physical exertion.
3. A burdened family history (known cases of sudden cardiac death in young relatives).
4. The presence of a pre-diagnosed organic heart disease in the patient.

Main clinical variants of syncope

Depending on the cause and mechanism of development, several types of syncopal states are distinguished.

Vasovagal (simple) syncope Is the most common variant. It is based on a sharp increase in vagus nerve tone (n. vagus). The triggers are pain, severe fright, psycho-emotional agitation, or being in a stuffy room (external hypoxia). This type does not occur during exertion, but may happen after it. The patient is usually standing at this moment. The development of the attack is preceded by a prodromal period: sharp weakness, nausea, sweating appear, and the patient feels hot or chills. Then the patient turns pale and «sinks down». Consciousness is lost for less than a minute. Special forms of vasovagal reactions occur during the Valsalva maneuver (straining with a closed glottis) and carotid sinus syndrome (reaction to pressure in the neck area).

Orthostatic syncope Occurs due to vasomotor reflex disorders (orthostatic hypotension) at the moment of a person's rapid transition from a horizontal to a vertical position. Most frequently provoked by the intake of antihypertensive drugs. The risk group also includes elderly patients and those who have been on strict bed rest for a long time.

Cough syncope (bettolepsy) A specific variant that develops at the height of an intense coughing fit. A typical patient with such syncope is a hypersthenic individual (plethoric, prone to obesity) who suffers from chronic bronchitis, smokes heavily, and frequently abuses alcohol.

Neurological syncopes May be the consequence of transient ischemic attacks (TIAs), severe migraines, or vertebrobasilar circulatory insufficiency. In the latter case, the attack is provoked by a sharp turn or hyperextension of the head, and the loss of consciousness is often accompanied by dizziness and diplopia (double vision).

Differential diagnosis with seizures

In addition to syncope, brief loss of consciousness is characteristic of epilepsy and hysterical conditions.

Epileptic seizures

• Convulsive variant: begins suddenly, accompanied by tonic-clonic convulsions, tongue biting, and involuntary urination. Due to the suddenness of the fall, the risk of severe head trauma is extremely high.
• Non-convulsive variant (absence): consciousness shuts down for just a few seconds, while motor phenomena (convulsions) are completely absent.

Hysterical (psychogenic) seizures Occur exclusively in the presence of spectators («in public»). The patient's movements are chaotic, yet coordinated and often aggressive toward others. Unlike epilepsy, there is no urinary or fecal incontinence, the patient does not bite their tongue and does not sustain severe injuries upon falling. Basic reactivity to the surroundings is preserved (the person looks frightened). A specific precursor is globus hystericus — a feeling of spasm and a «hysteric lump» rising in the throat before the attack begins.

First aid for simple fainting

Treatment of a typical (vasovagal) faint caused, for example, by severe fright, boils down to two simple actions:

1. Proper positioning: the patient must be laid down in such a way that the head is lower than the level of the torso. This is critically important for creating a pressure gradient and rapidly improving cerebral blood flow.
2. Reflex stimulation: mild irritating therapy is used — wiping the patient's face with cold water or carefully inhaling ammonia vapor.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Pathogenesis of carotid sinus syndrome and diagnostic rules.
• Hemodynamic features during the Valsalva maneuver.
• ECG criteria for life-threatening arrhythmias following syncope.
• Mechanisms of orthostatic hypotension development during antihypertensive therapy.
• Instrumental differential diagnosis of transient ischemic attacks (TIAs).

Other topics in the "Cardiovascular system" section

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