[[peripheral vascular resistance]] and [[cardiac output]] are the two main determinants for the presentation of syncope. [[autonomic nervous system]] impairment due to drugs or an autonomic failure, can lead to a decrease in [[peripheral vascular resistance]]. Reflex activity impairment may also cause a decrease of [[peripheral vascular resistance]], as the body normal compensation reflexes fail. Decrease in [[cardiac output]] may be due to venous pooling, cardioinhibitory reflexes, [[arrhythmia]], [[hypertension]], [[pulmonary embolism]], and volume depletion leading to diminished venous return, among others.
[[Peripheral vascular resistance]] and [[cardiac output]] are the two main determinants for the presentation of syncope. [[autonomic nervous system]] impairment due to drugs or an autonomic failure, can lead to a decrease in [[peripheral vascular resistance]]. Reflex activity impairment may also cause a decrease of [[peripheral vascular resistance]], as the body normal compensation reflexes fail. Decrease in [[cardiac output]] may be due to venous pooling, cardioinhibitory reflexes, [[arrhythmia]], [[hypertension]], [[pulmonary embolism]], and volume depletion leading to diminished venous return, among others.
===Life threatening Causes===
===Life threatening Causes===
Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.
Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.
More serious causes of syncope include cardiac (heart-related) causes such as an abnormal heart rhythm (an arrhythmia), where the heart beats too slowly, too rapidly or too irregularly to pump enough blood to the brain. Other important cardio-vascular conditions that can be manifested by syncope include subclavian steal syndrome and aortic stenosis. Vasovagal (situational) syncope, one of the most common types, may occur in scary or embarrassing situations or during blood drawing, coughing, or urinating
↑Nishida, K.; Hirota, SK.; Tokeshi, J. (2008). "Laugh syncope as a rare sub-type of the situational syncopes: a case report". J Med Case Rep. 2: 197. doi:10.1186/1752-1947-2-197. PMID18538031.
↑Benbadis, SR.; Chichkova, R. (2006). "Psychogenic pseudosyncope: an underestimated and provable diagnosis". Epilepsy Behav. 9 (1): 106–10. doi:10.1016/j.yebeh.2006.02.011. PMID16697264. Unknown parameter |month= ignored (help)