Cardiac
Heart-related causes may include an abnormal heart rhythm, problems with the heart valves or heart muscle, or blockages of blood vessels from a pulmonary embolism or aortic dissection, among others. Cardiac arrhythmias
The most common cause of cardiac syncope is cardiac arrhythmia (abnormal heart rhythm) wherein the heart beats too slowly, too rapidly, or too irregularly to pump enough blood to the brain. Some arrhythmias can be life-threatening.Two major groups of arrhythmias are bradycardia and tachycardia. Bradycardia can be caused by heart blocks. Tachycardias include SVT (supraventricular tachycardia) and VT (ventricular tachycardia). SVT does not cause syncope except in Wolff-Parkinson-White syndrome. Ventricular tachycardia originate in the ventricles. VT causes syncope and can result in sudden death. Ventricular tachycardia, which describes a heart rate of over 100 beats per minute with at least three irregular heartbeats as a sequence of consecutive premature beats, can degenerate into ventricular fibrillation, which is rapidly fatal without cardiopulmonary resuscitation (CPR) and defibrillation.Long QT syndrome can cause syncope when it sets off ventricular tachycardia or torsades de pointes. The degree of QT prolongation determines the risk of syncope. Brugada syndrome also commonly presents with syncope secondary to arrhythmia.Typically, tachycardic-generated syncope is caused by a cessation of beats following a tachycardic episode. This condition, called tachycardia-bradycardia syndrome, is usually caused by sinoatrial node dysfunction or block or atrioventricular block. Obstructive cardiac lesion
Blockages in major vessels or within the heart can also impede blood flow to the brain. Aortic stenosis and mitral stenosis are the most common examples.
This is a portable ECG device that can record the wearers heart rhythms during daily activities over an extended period of time. Since fainting usually does not occur upon command, a Holter monitor can provide a better understanding of the hearts activity during fainting episodes. For people with more than two episodes of syncope and no diagnosis on "routine testing", an insertable cardiac monitor might be used. It lasts 28–36 months and is inserted just beneath the skin in the upper chest area. Imaging
Echocardiography and ischemia testing may be recommended for cases where initial evaluation and ECG testing is nondiagnostic. For people with uncomplicated syncope (without seizures and a normal neurological exam) computed tomography or MRI is not generally needed. Likewise, using carotid ultrasonography on the premise of identifying carotid artery disease as a cause of syncope also is not indicated. Although sometimes investigated as a cause of syncope, carotid artery problems are unlikely to cause that condition. Additionally an electroencephalogram (EEG) is generally not recommended. A bedside ultrasound may be performed to rule out abdominal aortic aneurysm in people with concerning history or presentation. Differential diagnosis
Other diseases which mimic syncope include seizure, low blood sugar, and certain types of stroke. While these may appear as "fainting", they do not fit the strict definition of syncope being a sudden reversible loss of consciousness due to decreased blood flow to the brain. Management
Management of syncope focuses on treating the underlying cause. This can be challenging as the underlying cause is unclear in half of all cases.