Causes of Syncope
| A. Neurally Mediated Syncope |
| Vasovagal syncope |
| Provoked fear, pain, anxiety, intense emotion, sight of blood, unpleasant sights and odors, orthostatic stress |
| Situational reflex syncope |
| Pulmonary |
| Cough syncope, wind instrument player's syncope, weightlifter's syncope, “mess trick”a and “fainting lark,”b sneeze syncope, airway instrumentation |
| Urogenital |
| Postmicturition syncope, urogenital tract instrumentation, prostatic massage |
| Gastrointestinal |
| Swallow syncope, glossopharyngeal neuralgia, esophageal stimulation, gastrointestinal tract instrumentation, rectal examination, defecation syncope |
| Cardiac |
| Bezold-Jarisch reflex, cardiac outflow obstruction |
| Carotid sinus |
| Carotid sinus sensitivity, carotid sinus massage |
| Ocular |
| Ocular pressure, ocular examination, ocular surgery |
| B. Orthostatic Hypotension |
| Primary autonomic failure due to idiopathic central and peripheral neurodegenerative diseases—the “synucleinopathies” |
| Lewy body diseases |
| Parkinson's disease |
| Lewy body dementia |
| Pure autonomic failure |
| Multiple system atrophy (the Shy-Drager syndrome) |
| Secondary autonomic failure due to autonomic peripheral neuropathies |
| Diabetes |
| Hereditary amyloidosis (familial amyloid polyneuropathy) |
| Primary amyloidosis (AL amyloidosis; immunoglobulin light chain associated) |
| HSAN (especially type III—familial dysautonomia) |
| Idiopathic immune-mediated autonomic neuropathy |
| Autoimmune autonomic ganglionopathy |
| Sjögren's syndrome |
| Paraneoplastic autonomic neuropathy |
| HIV neuropathy |
| Postprandial hypotension |
| Iatrogenic (drug-induced) |
| Volume depletion |
| C. Cardiac Syncope |
| Arrhythmias |
| Sinus node dysfunction |
| Atrioventricular dysfunction |
| Supraventricular tachycardias |
| Ventricular tachycardias |
| Inherited channelopathies |
| Cardiac structural disease |
| Valvular disease |
| Myocardial ischemia |
| Obstructive and other cardiomyopathies |
| Atrial myxoma |
| Pericardial effusions and tamponade |
aHyperventilation for ~1 min, followed by sudden chest compression.
bHyperventilation (~20 breaths) in a squatting position, rapid rise to standing, then Valsalva.
Abbreviation: HSAN, Hereditary sensory and autonomic neuropathies.