Lightheadedness
The inability of the upper chambers of the heart to contract in rhythm with the lower chambers produces an abnormal heart rate. The irregular heart rates cause a reduction in the supply of oxygenated blood to the brain to other body organs. The person feels lightheaded due to a substantial drop in blood pressure in the patient of atrial fibrillation. Poor blood circulation to the brain results in the sensation of fainting or even causes the patient to pass out as the blood pressure drops extremely.