Causes of Syncope

Head	CVA / TIA Seizure Cancer Orthostatic hypotension Carotid stenosis Psychosis
Heart	Myocardial infarction Arrhythmia tachycardia / bradycardia / Long QT Syndrome / Brugada Syndrome / WPW Aortic stenosis Obstructive cardiomyopathy Pacemaker malfunction Pericardial tamponade
Lungs	Pulmonary Embolism Tension pneumothorax
Vessels	Hypovolemia ↓ intake / ↑ loss Toxins drugs / alcohol / Prescription Rx Electrolytes Ammonia (hepatic encephalopathy) Vasodilation sepsis / anaphylaxis / heat Aortic Dissection Ruptured AAA Anemia Vasovagal (neurocardiogenic) See Below
Vasovagal Etiologies (Neuro-cardiogenic)	Carotid massage tie tightening / shaving Defecation / Micturition Post-prandial Post-exercise Cough / sneeze Trumpet playing Weight lifting Prolonged standing Bezold-Jarisch Reflex pain / fright / emotion / blood loss / needles See Below

Bezold-Jarisch Reflex Explained Briefly

Common cause of Neuro-cardiogenic syncope (aka, vasovagal syncope)

**Adrenergic stimuli (pain/emotion)**

--> Exaggerated catecholamine release

↑ Sympathetic tone ++

↑ β1 contractility, before α1 can ↑preload

↑ Ventricular contraction on under-filled chamber

↑ Mechanoreceptor activation from exaggerated contractile force

--> Homeostatic vagal tone

↑ Vasodilation / Bradycardia ++

--> SYNCOPE

References

Kaye, GC. Arthur, W. The pathophysiology of common causes of syncope. Postgrad Med J2000;76:750-753. doi:10.1136/bmj.76.902.750

Brignole. M. Diagnosis and treatment of syncope. Heart. 2007 Jan; 93(1): 130–136. doi:10.1136/hrt.2005.080713