Syncope toolkit

Vasovagal syncope

In this section:

Reflex syncope (also called neurally mediated syncope)

There are primarily two mechanisms of reflex syncope:

Vasodepression - insufficient sympathetic tone resulting in dilation of blood vessels leading to pooling of blood in the splanchnic bed, pelvis and lower limbs. This reduces venous return and stroke volume, ultimately causing hypotension. This is the ‘vaso’ part of vasovagal.
Cardioinhibition - occurs later than vasodepression and less frequently in the older patient. It presents as increased parasympathetic tone causing bradycardia or asystole. This is the ‘vagal’ part of vasovagal.

Types of reflex syncope

Vasovagal

Orthostatic vasovagal syncope - can occur when standing (although 10% of vasovagal syncope episodes occur in people when sitting or rarely when supine)
Emotional - can occur with pain, medical instrumentation, sight of blood or needles.

Reflex syncope is more likely to occur when several risk factors or triggers occur at the same time. Patients typically experience activation of the autonomic nervous system resulting in sweating, flushing, pallor, and palpitations, and reduced blood pressure that reduces cerebral perfusion. This can result in light-headedness and altered vision and hearing. Symptoms rapidly improve upon assuming a horizontal position.

Reflex syncope is the most common type of syncope presenting to GPs. Patients often describe a family history of vasovagal syncope.

There are two peaks in incidence of vasovagal syncope, one in adolescents, a little more common in females and a second in older age, a little more common in males. Episodes often occur in clusters and then improve for reasons that are not well understood. Patients who experience frequent episodes have a significantly reduced quality of life.

Management of reflex syncope

Situational syncope

Micturition, defaecation, swallowing, cough, sneeze, laughing, trumpet blowing
Post-exercise.

Carotid sinus syndrome (CSS)

Carotid sinus hypersensitivity (CSH) – when a hypersensitive carotid sinus is stimulated by cartoid sinus massage (CSM), in an asymptomatic patient, causing a ventricular pause of over three seconds, and/or drop in blood pressure of over 50 mmHg.
Carotid sinus syndrome (CSS) is CSM causing syncope in a patient with a history of syncope and symptom reproduction.

CSS usually occurs in older men with pre-existing cardiovascular disease. CSS is diagnosed by history and carotid sinus massage. This should be undertaken upright and supine in a specialist unit with beat to beat recording of heart rate and blood pressure.

Vasovagal syncope in younger children

Vasovagal syncope in younger children, also called reflex anoxic seizures (RAS), infantile reflex syncopal attacks or pallid breath-holding spells. RAS and pallid breath-holding spells are confusing terms as these episodes do not involve breath-holding or seizures.

Following an unpleasant stimulus, the child loses consciousness due to cardio-inhibitory vasovagal syncope. Care must be taken to differentiate this from structural or electrical cardiac pathology by history, examination and ECG and referral to a paediatrician may be indicated. Management of RAS is usually explanation and reassurance as it always resolves, and pacing should generally be avoided unless extremely incapacitating.

Support for parents can be obtained from the Syncope Trust And Reflex anoxic Seizures (STARS).