Dizzy spells/Fainting

Dizzy spells or fainting can be due to a variety of factors – heart rhythm disturbances, low blood pressure, slow heart rate, fast heart rate, dehydration, inner ear problems (vertigo), epilepsy, anxiety, infections, just to name a few.

Determining the cause of dizzy spells can be difficult, and requires very good history taking, thorough clinical examination, and careful selection of tests.

From the heart viewpoint, dizzy spells can be symptomatic of conditions that give rise to inadequate blood supply to the brain, leading to a reflex action resulting in the head being positioned horizontal with the heart (rather than upright, or head above heart level).

Here is the link to the Merck Manual regarding fainting.