Known medically as “syncope,” fainting occurs when there isn’t enough blood going to the brain. Certain non-cardiac conditions can make a person lose consciousness (for instance, having a seizure), but fainting caused by a heart problem usually means that the blood pressure has dropped too low. This can occur from dehydration, too much blood pressure medication, or various things that activate the “vagus” nerve in the brain, such as pain, fear, or abdominal cramps. More concerning causes of cardiac fainting are arrhythmias: abnormal heart rhythms that lead to low blood pressure—usually very fast or very slow heart rates. Cardiologists will often want to perform ambulatory electrocardiographic monitoring and echocardiography as an initial evaluation of syncope.