Pro Physician’s Petty Pearls ( Vasovagal Syncope )

In school, every Monday before classes we used to have general assemblies, which included prayers, hymns, the day’s news, important announcements made by our Principal and concluded with the school anthem. This was held in an open ground for about 30-40 minutes, and for this while we would stand in attention position.
Assembly Line
Frequently during these assemblies, there would be 2-3 of us fainting and our teachers scurrying to assist them. Although the fainting bouts were often blamed on missing breakfasts (leading to weakness) or the scorching sun, I noticed that even the seemingly sturdy girls or those lucky ones standing in the shade would be no exception and also the argument was not valid for the winter “falls”!
So, what led to this random episode of fainting - I wondered.
PROLONGED STANDING in the same posture!!!!
(During the 1st year in med college, I came to know this as one of the many causes of fainting or syncope, and this one seems apt in this scenario.)
Fig 1
You might have guessed that standing for a considerably long time leads to fainting because of GRAVITY. Yes, but that’s partially correct! To understand this well, let’s take a quick glance at the picture of the veins of the lower limbs. (Fig 1) The characteristic feature of these veins is that they are highly distensible i.e. the diameter and thus volume of the vessels increases with an increase in venous pressure. So when we are standing in an erect posture for a prolonged time, pooling of blood occurs into these veins with the assistance of gravity.
Due to the blood accumulation in the veins, the volume of blood returning to the heart decreases meaning a decreased Venous Return (VR). Since in the steady state the Venous Return equals Cardiac Output (CO) over a span of time, ↓VR leads to ↓CO. The term Cardiac Output (in cardiac physiology) describes the volume of blood pumped by either ventricle per unit time. (Fig 2)

Fig 2
The amount of blood delivered to the body tissues is related to the CO, so less blood reaches the various organs of the body (i.e. decreased perfusion of organs). The organ that is most affected is the brain, even being located far above the heart. A decreased blood flow to the brain and then drop in oxygen level there results into fainting as a compensatory mechanism, because on adopting a horizontal position the VR and CO rises, so the blood flow to the brain improves thus regaining consciousness. (Fig 3) In medical terms, this is called Vasovagal Syncope, which in itself is not harmful unless recurs frequently and in that case visit a Doctor.

Fig 3
In daily life, on several occasions, we all have to stand for a considerably longer time at a stretch like while teaching, travelling, giving a speech, (https://www.theguardian.com/world/2016/aug/22/singaporean-prime-minister-lee-hsien-loong-faints-during-televised-speech) or in intro sessions with seniors! So you might be curious to know if there is any way to prevent this.
Yes, there is!
As you stand straight squirm your toes (make twisting movements), contract your leg muscles or move about. Most importantly keep yourself hydrated.


How these simple acts could prevent fainting, can also be medically explained. If you are curious to know the details do let me know in the comment section, I will provide the explanation.

                                                                                                                ~ Debjani Das




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