Vasovagal syncope

Different types of vasovagal syncope

• Young patients
• Old patients
• Post-exercise Syncope
• Blood phobia
• Blood donation
• Vasovagal syncope during sleep

Triggers for Vasovagal Syncope

Vasovagal syncope can occur after exposure of a lot of different triggers. Recognised triggers for vasovagal syncope are prolonged orthostatic stress, blood drawing, medical instrumentation and psychological stressors.

Psychological stressors

Psychological stressors include:

• Stirring emotional news or witnessing a distressing accident [1],[2]
• Unexpected pain or threat [1],[3]
• Unpleasant smells may trigger vasovagal syncope [4],[5]
• During blood drawing,
• Vaccination [6]
• Instrumentation, pain of the procedure may contribute to vasovagal syncope
• Sharp pain is reported to be an important factor during arterial blood sampling [7].
• Blood phobia: However, in a patient with blood phobia just thinking or talking about blood drawing may elicit a common faint [8]

Vasovagal syncope in airliners

Vasovagal episodes are the most common in-flight medical events, and may affect patients of all ages [9]. The following may all predispose vasovagal faints during air travel [10]:

• Prolonged motionless sitting
• The use of alcohol
• Anxiety
• Mild hypoxia during air travel

Cabin pressure in commercial aircraft is usually adjusted to the equivalent of an altitude of 1500 to 2500 m above sea level. It appears that hypoxic syncope results from the super-imposed vasodilator effects of hypoxia on the cardiovascular system [11].

Treatment

Patients, who otherwise never experienced a (severe) vasovagal episode may suffer from convulsive syncope during air travel [12]. These patients should be advised to have:

• A high salt intake in the days prior to travelling by plane
• Reduce anti-hypertensive medication –if feasible-
• And drink non-alcoholic beverages galore during the trip.

Especially during long flights (> 2 hours) they should perform in-chair muscle tensing and relaxing exercise and have a regular walk through the isle. In recurrent cases midodrine prior to flying or supportive stockings can be considered.

Sleep vasovagal syncope

Sleep vasovagal syncope is defined as loss of consciousness in a non-intoxicated adult occurring during the night (e. g. 10:00 pm to 7:00 am), in which the patient wakes up with pre-syncopal and abdominal symptoms (i.e. an urge to defecate) and losses consciousness in bed or immediately upon standing.
There is no tongue biting or post-ictal confusion. There is usually a history of daytime vasovagal syncope and there seems to be a more pronounced fear of blood and medical procedures than in other syncope patients [13]. Physical examination, ECG and EEG are within normal limits. The vasovagal reaction is thought to start while asleep [14][15], and continuing after waking up, hence the name. During syncope there may be a profound sinus-bradycardia [14]. Vasovagal sleep syncope occurs at all ages.

Differential Diagnosis

Sleep vasovagal syncope is diagnosed by excluding beyond reasonable doubt the hereafter mentioned disorders [15].
Epilepsy is the foremost alternative diagnosis to consider, but can often easily be ruled out on clinical grounds. Complex partial, generalized tonic-clonic and myoclonic epilepsy may occur during sleep and can imitate syncope when causing cause sinus-bradycardia [16].
There are a number of related conditions, including “abdominal epilepsy” and Panayiotopoulos syndrome (typically with vomiting) [17], in which the associated clinical features are abdominal pain and confusion.
Sleep paralysis and hypnogogic hallucinations occur in narcolepsy but also as isolated phenomena, mostly with other characteristic features in the history (e. g., daytime somnolence, in contrast to syncope there’s no amnesia.) and abnormal polysomnography, which can also be used to diagnose sleep apnoea and night terrors.
Occasionally cardiac disorders may cause cardiac arrhythmias during sleep. Most of these are unlikely if the 12-lead ECG is normal, and in some patients long-term ambulatory ECG monitoring is required [18].
Some patients with a diagnosis of defaecation syncope (see below) described abdominal and pre-syncopal symptoms that started simultaneously during sleep [19][20] there may be some overlap between this condition and sleep syncope [15].

References

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2. Engel GL, Romano J, & McLin TR (1944). Vasodepressor and carotid sinus syncope - clinical, eletroencephalographic and electrocardiographic observations. Arch Intern Med 74, 100-119.

3. GREENFIELD AD (1951). An emotional faint. Lancet 1, 1302-1303.

4. Engel GL & Romano J (1947). Studies of Syncope: IV. Biologic interpretation of vasodepressor syncope. Psychosom Med 9, 288-294.

5. Ganzeboom KS, Colman N, Reitsma JB, Shen WK, and Wieling W. Prevalence and triggers of syncope in medical students. Am J Cardiol. 2003 Apr 15;91(8):1006-8, A8. DOI:10.1016/s0002-9149(03)00127-9 |
6. Braun MM, Patriarca PA, and Ellenberg SS. Syncope after immunization. Arch Pediatr Adolesc Med. 1997 Mar;151(3):255-9. DOI:10.1001/archpedi.1997.02170400041007 |

7. Rushmer, R.F. Circulatory collapse following mechanical stimulation of arteries. Am. J. Physiol. 1944;141:722.

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17. Covanis A. Panayiotopoulos syndrome: a benign childhood autonomic epilepsy frequently imitating encephalitis, syncope, migraine, sleep disorder, or gastroenteritis. Pediatrics. 2006 Oct;118(4):e1237-43. DOI:10.1542/peds.2006-0623 |
18. Brierley EJ, Jackson MJ, Clark RS, and Kenny RA. Alarming asystole. Lancet. 2001 Jun 30;357(9274):2100. DOI:10.1016/s0140-6736(00)05184-9 |
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