5. Seizures
The consequences of poor oxygenation can be very bad for our brain. Our neurons and other brain cells burn glucose in order to work, and the glucose is provided by the constant flow of blood that goes up to our brain through the carotids and the basal artery.
The irrigation system in our brain is designed to prevent blood shortage as much as possible, but with a disturbed heartbeat such as what happens with the Long QT syndrome, sometimes it is not enough and our neurons suffer because of it.
The most common consequence of a poor blood supply aside from fainting is seizures, which are a massive malfunction of the synapsis that connect one neuron and the next. Without the proper blood input, our neuronal activity can go out of control and induce massive discharges of neurotransmission and electrolytes that activate our brain cells and cause seizures.