An Overview of the Physiology and Pathophysiology of Syncope

Question 1

what is Transient Loss of Consciousness (TLOC)

Answer 1

A state of real or apparent loss of consciousness with loss of awareness, characterized by amnesia for the period of unconsciousness, loss of motor control, loss of responsiveness, and a short duration

Question 2

what is syncope

Answer 2

Transient loss of consciousness due to cerebral hypoperfusion, characterized by rapid onset, short duration, and spontaneous complete recovery

Question 3

what are the 3 categories that syncope be

Answer 3

Reflex Syncope
Orthostatic Hypotension
Cardiac Syncope

Question 4

what is reflex syncope

Answer 4

• it is common
• When activated, the reflex causes cardioinhibition through vagal stimulation. This decreases heart rate (Bradycardia) and cardiac output (CO)
• And/or vasodepression through depression of sympathetic activity to blood vessels. This decreases systemic vascular resistance (Vasodilatation), venous return, stroke volume and CO

The decrease in CO and SVR, decreases mean arterial blood pressure (MAP)

Resulting in cerebral hypoperfusion and syncope or near syncope

Question 5

what is the most common type of syncope

Answer 5

vasovagal

Question 6

what triggers the fainting in vasovagal syncope

Answer 6

emotional distress and orthostatic distress

• is also associated with pallor, sweating and nausea

Question 7

what is the main risk of vasovagal reflex syncope

Answer 7

risk of injury when falling

Question 8

what is the treatment for vasovagal reflex syndrome

Answer 8

education, reassurance, avoidance of triggers (if possible) and adequate hydration

Question 9

what triggers the fainting in situational reflex syncope

Answer 9

during or immediately after a specific trigger e.g. cough, micturition, swallowing, etc

Question 10

what is the treatment of situational reflex syncope

Answer 10

• treat cause if possible eg cough
• avoid dehydration and excessive alcohol
• Cardiac permanent pacing may be needed in some cases of situational syncope

Question 11

what triggers carotid sinus syncope

Answer 11

mechanical manipulation of the neck, shaving, tight collar
- may occur after head and neck surgery or radiation

Question 12

what is carotid sinus reflex syncope more common in

Answer 12

the elderly in particular men

Question 13

treatment for Carotid Sinus Reflex Syncope

Answer 13

Cardiac permanent pacing is generally recommended

Question 14

risk factors for Postural (Orthostatic) Hypotension

Answer 14

Age related
Medications
Certain diseases
Reduced intravascular volume
Prolonged bed rest

Question 15

how is a positive result indicated for Postural (Orthostatic) Hypotension

Answer 15

a drop, within 3 minutes of standing from lying position:

• in systolic blood pressure of at least 20 mmHg (with or without symptoms) or
• a drop in diastolic blood pressure of at least 10 mm Hg (with symptoms)

Question 16

symptoms of Postural (Orthostatic) Hypotension

Answer 16

cerebral hypoperfusion such as: lightheadedness, dizziness, blurred vision, faintness and falls

Question 17

what causes a cardiac syncope

Answer 17

caused by a cardiac event resulting in sudden drop in cardiac output

Question 18

Cardiac syncope can be caused by:

Answer 18

Arrhythmias: resulting in bradycardia or tachycardia

Acute Myocardial infraction

Structural Cardiac Disease: e.g. aortic stenosis, hypertrophic cardiomyopathy

Other Cardiovascular Disease: e.g. pulmonary embolism, aortic dissection

Question 19

what are the Features that Suggest a Cardiac Syncope

Answer 19

Syncope during excretion or when supine

Presence of a structural cardiac abnormality or coronary heart disease

A family history of sudden death at young age

Sudden onset palpitations immediacy followed by syncope

Findings on ECG suggestive of arrhythmic syncope