Vasovagal syncope

• Young patients
• Old patients
• Post-exercise Syncope
• Blood phobia
• Blood donation

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]

Post-exercise vasovagal syncope

Syncope after exercise is often neurally mediated, i.e. post-exercise vasovagal syncope. This condition is typically diagnosed in young fit, furthermore healthy young patients. Foremost, the diagnostic workup of all patients presenting with exercise-related syncope is aimed at excluding dangerous cardiac conditions and includes echocardiography and exercise testing [9]. Risk factors for a cardial problem are fainting while sitting or supine and suddenly fainting during exercise without presyncope.
Characteristically, syncope may occur while the individual is standing motionless during the first five to ten minutes after exercise [10]. Especially athletes in the (ultra) endurance sports are at risk for post exercise vasovagal syncope e.g. after marathon swimming [11] or marathon running [12][13][14]. Vasovagal syncope after routine treadmill testing is rare (estimated 0,2% [15]). However, when treadmill testing is immediately followed by passive head-up tilt testing, this percentage can increase up to 50-70% [10]. Vasovagal syncope after exercise is considered to be a benign occurrence [9].

Muscle pump

During exercise, rhythmically contracting skeletal muscles in the lower part of the body reduce the degree of venous pooling by squeezing veins, thereby increasing the venous return of blood to the heart. This phenomenon is known as the ‘muscle pump. The sudden removal of the muscle pump after stopping exercise decreases cardiac preload which, together with a rapid return of vagal tone, may promote vasovagal syncope.

Vasovagal syncope in airliners

Vasovagal episodes are the most common in-flight medical events, and may affect patients of all ages [16]. The following may all predispose vasovagal faints during air travel [17]:

• 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 [18].

Treatment

Patients, who otherwise never experienced a (severe) vasovagal episode may suffer from convulsive syncope during air travel [19]. 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 [20]. Physical examination, ECG and EEG are within normal limits. The vasovagal reaction is thought to start while asleep [21][22], and continuing after waking up, hence the name. During syncope there may be a profound sinus-bradycardia [21]. Vasovagal sleep syncope occurs at all ages.

Differential Diagnosis

Sleep vasovagal syncope is diagnosed by excluding beyond reasonable doubt the hereafter mentioned disorders [22].
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 [23].
There are a number of related conditions, including “abdominal epilepsy” and Panayiotopoulos syndrome (typically with vomiting) [24], 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 [25].
Some patients with a diagnosis of defaecation syncope (see below) described abdominal and pre-syncopal symptoms that started simultaneously during sleep [26][27] there may be some overlap between this condition and sleep syncope [22].

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.

8. Van Dijk N, Velzeboer SC, Destrée-Vonk A, Linzer M, and Wieling W. Psychological treatment of malignant vasovagal syncope due to bloodphobia. Pacing Clin Electrophysiol. 2001 Jan;24(1):122-4. DOI:10.1046/j.1460-9592.2001.00122.x |
9. Krediet CT, Wilde AA, Wieling W, and Halliwill JR. Exercise related syncope, when it's not the heart. Clin Auton Res. 2004 Oct;14 Suppl 1:25-36. DOI:10.1007/s10286-004-1005-1 |
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12. Grady GF, Rodman M, and Larsen LH. Hepatitis B antibody in conventional gamma-globulin. J Infect Dis. 1975 Oct;132(4):474-7. DOI:10.1093/infdis/132.4.474 |
13. Holtzhausen LM and Noakes TD. The prevalence and significance of post-exercise (postural) hypotension in ultramarathon runners. Med Sci Sports Exerc. 1995 Dec;27(12):1595-601.
14. Holtzhausen LM and Noakes TD. Collapsed ultraendurance athlete: proposed mechanisms and an approach to management. Clin J Sport Med. 1997 Oct;7(4):292-301.
15. Schlesinger Z. Letter: Life-threatening "vagal reaction" to physical fitness test. JAMA. 1973 Nov 26;226(9):1119.
16. Gendreau MA and DeJohn C. Responding to medical events during commercial airline flights. N Engl J Med. 2002 Apr 4;346(14):1067-73. DOI:10.1056/NEJMra012774 |
17. Sutton R. Vasovagal syncope: prevalence and presentation. An algorithm of management in the aviation environment. Eur Heart J Suppl. 1999 Apr;1 Suppl D:D109-13.
18. Halliwill JR and Minson CT. Cardiovagal regulation during combined hypoxic and orthostatic stress: fainters vs. nonfainters. J Appl Physiol (1985). 2005 Mar;98(3):1050-6. DOI:10.1152/japplphysiol.00871.2004 |
19. Wieling W, Krediet CT, and Wilde AA. Flush after syncope: not always an arrhythmia. J Cardiovasc Electrophysiol. 2006 Jul;17(7):804-5. DOI:10.1111/j.1540-8167.2006.00520.x |

20. Jardine DL, Krediet CT, Cortelli P, & Wieling W (2006b). Sleep syncope: clinical features and autonomic profiles. Clin Auton Res 16, 321-322.

21. Krediet CT, Jardine DL, Cortelli P, Visman AG, and Wieling W. Vasovagal syncope interrupting sleep?. Heart. 2004 May;90(5):e25. DOI:10.1136/hrt.2003.031294 |
23. Tinuper P, Bisulli F, Cerullo A, Carcangiu R, Marini C, Pierangeli G, and Cortelli P. Ictal bradycardia in partial epileptic seizures: Autonomic investigation in three cases and literature review. Brain. 2001 Dec;124(Pt 12):2361-71. DOI:10.1093/brain/124.12.2361 |
24. 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 |
25. 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 |
26. Pathy MS. Defaecation syncope. Age Ageing. 1978 Nov;7(4):233-6. DOI:10.1093/ageing/7.4.233 |
27. Fisher CM. Syncope of obscure nature. Can J Neurol Sci. 1979 Feb;6(1):7-20. DOI:10.1017/s0317167100119316 |