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syncope

Definition: - transient loss of consciousness & postural tone (i.e. falling when standing, slumping over when sitting, etc.) followed by spontaneous recovery without the need for resuscitation Etiology: (also see causes of syncope) 1) inadequate vasoconstrictor mechanisms a) neurocardiogenic vasopressor dysfunction (NVD) accounts for the majority of syncopal episodes in the general population (neurally-mediated syncope) [5] 1] vasovagal reaction 2] carotid sinus syncope (most common cause in elderly) 3] situational syncope a] micturition syncope b] defection syncope c] postprandial syncope d] cough syncope e] heat syncope f] swallowing ? [16] b) postural hypotension (orthostasis) c) postprandial hypotension d) autonomic insufficiency - primary autonomic insufficiency - multiple system atrophy [62] - Parkinson's disease [62] - sympathectomy, pharmacologic or surgical - diabetes mellitus [16, 62] - uremia [16,62] - spinal cord lesions [62] e) diseases of the CNS & peripheral nervous system 1] syncope associated with brainstem neurological signs & symptoms - brainstem stroke [16] 2] posterior circulation vascular disease (vertebrobasilar system) f) increased bradykinin g) vasodilator agent h) tricyclic antidepressants [16] 2) hypovolemia a) blood loss b) Addison's disease c) dehydration d) diuretics 3) venous pooling a) mechanical reduction of venous return - Valsalva maneuver - cough - micturition - atrial myxoma, ball valve thrombus b) nitrates 4) reduced cardiac output a) obstruction to left ventricular outflow 1] aortic stenosis 2] hypertrophic subaortic stenosis b) obstruction to pulmonary flow 1] pulmonic stenosis 2] pulmonary embolus (under-diagnosed) [7,29] - identified in 17% of patients with syncope [53] - higher-than-expected prevalence of pulmonary embolisn among patients with syncope but without chest pain or dyspnea, 2.2% overall, but 18% of patients with cancer [57] 3] pulmonary hypertension c) myocardial infarction with pump failure d) cardiac tamponade e) dilated cardiomyopathy [5] f) negative inotropes g) atrial myxoma [5] 5) tachydysrhythmias a) ventricular tachycardia 1] ventricular fibrillation 2] prolonged QT syndrome 3] torsades de pointes (donepezil) 4] Brugada syndrome b) atrial fibrillation with rapid ventricular response [60] - RR of cardiac syncope for atrial fibrillation = 7.3 [56] c) AV nodal re-entry tachycardia d) pre-excitation disorder with atrial fibrillation/flutter e) pharmaceuticals 6) bradyarrhythmias* a) AV block 2nd & 3rd degree with Stokes-Adams attacks b) ventricular asystole c) sinus bradycardia 1] sinoatrial block 2] sinus arrest 3] sick sinus syndrome* d) carotid sinus syndrome (most common cause in elderly) e) glossopharyngeal neuralgia & other painful states f) pharmacutical agents 1] beta blockers 2] alpha-blockers (doxazosin, terazosin) 3] calcium channel blockers 4] antiarrhythmic drugs 5] cholinesterase inhibitors (donepezil) 7) vascular anomalies a) dissecting aneurysm b) subclavian steal syndrome c) vertebrobasilar TIA [5] d) pulmonary embolism - 15% of patients evaluated with CTPA or VQ scan [45] - 1% in hospitalized patients [46] - < 1% (all patients), 0.4-2.6% in hospitalized patents [48] 8) hypoglycemia [16]: hypoglycemic agent 9) pharmaceuticals (see above) 10) psychogenic pseudosyncope 11) idiopathic (20-40%) [8,12,16] 12) predisposition to syncope in the elderly a) multifactorial etiology [16] b) decreased arterial compliance c) decreased reflex peripheral vasoconstriction d) systolic hypertension e) left ventricular hypertrophy (LVH) f) diastolic dysfunction g) hypotensive response to increased heart rate, volume depletion or loss of atrial contraction 13) also see Differential diagnosis: (below) * bradyarrhythmia due to carotid sinus syncope most common cause in the elderly [5,16,20] Epidemiology: 1) syncope occurs in 30-50% of people at some point in their lives 2) 3% of emergency department visits & 1% of hospitalizations are due to syncope 3) incidence of syncope increase with age [16] 4) age > 50, male sex & known structural heart disease favors cardiac versus neurally-mediated syncope Pathology: - cerebral hypoperfusion - age-related changes predispose to syncope a) reduced baroreflex increase in heart rate & sympathetic peripheral vascular constriction b) reduced left ventricular compliance may reduce left ventricular filling with increases in heart rate c) changes in endocrine & renal function may predispose to dehydration [16] History: 1) obtain history from a) patient b) witnesses - eyewitness accounts of stiff limbs, twitches of all limbs, facial color, drooling, head deviation may be correct 1/2 of the time [11] c) medical responders to scene of event 2) obtain details on: a) circumstances, place, time, posture, duration b) pattern of syncope, if multiple events c) relationship to: fasting, eating, daily activities or routines, associated illnesses, bodily functions, exertion, sleep deprivation d) premonitory symptoms 1] palpitations 2] nausea 3] abdominal discomfort 4] pallor 5] diaphoresis 6] chest pain 7] dyspnea e) recovery symptoms f) anemia or GI bleeding g) family history may suggest syncope due to arrhythmia a) long QT syndrome b) Brugada syndrome c) hypertrophic obstructive cardiomyopathy d) sudden death h) detailed medication history 1] over-medication (generic & brand names) a] vasoactive agents b] arrhythmogenic agents 2] recent adjustment of medication doses 3] cholinesterase inhibitors (donepezil) 4) syncope during exercise or family history of sudden death suggests cardiac cause of syncope [23] - syncope during exertion suggests hypertrophic cardiomyopathy [5] - cyanosis witnessed during syncopal episode suggests cardiac syncope [56] 5) past medical history - previous history of syncope or prodrome suggesting vasovagal reaction - prior history of heart failure, or myocardial infarction - depression Physical examination: - vitals - orthostatic blood pressure & pulse, including supine, sitting & upright for 3 minutes [44] - cardiac examination (heart sounds, murmurs) - carotid pulse & auscultation - focal neurologic deficits [62] - signs of volume depletion [62] - gait & balance evaluation - leg crossing, squatting or hand grip maneuvers for vasovsgal syncope with prolonged prodrome [5] Clinical manifestations: 1) nausea &/or diaphoresis a) may precede neurocardiogenic syncope b) may accompany ischemic heart disease in older adults 2) onset of syncope due to cardiac dysrhythmia - generally abrupt (< 5 seconds of warning or no warning) - palpitations may or may not be noted - syncope during exertion suggests hypertrophic cardiomyopathy - syncope during sleep suggests long QT syndrome or Brugada syndrome [5] 3) transient loss of consciousness 4) loss of postural tone a) orthostatics by far the most useful diagnostic test [5] b) identifies etiology of syncope in 15-21% of cases c) affected diagnosis & management in ~25% of cases [12] 5) full recovery generally occurs after a short time a) feeling of fatigue many accompany neurocardiogenic syncope b) little to no post-event confusion 6) seizures may occur secondary to syncope 7) multifocal myoclonus occurs in most patients with syncope 8) vertebrobasilar TIA or stroke - vertigo more likely than lightheadedness - blood pressure likely increased - brain-stem symptoms likely with vertebrobasilar stroke 9) urinary incontinence may allegedly occur due to relaxation of urinary sphincter [16] Laboratory: 1) complete blood count (CBC) for anemia* 2) fecal occult blood [62] 3) serum chemistries a) renal function tests b) electrolytes (electrolyte disorder = high short-term risk) [5] c) drug levels of therapeutically monitored drugs 4) markers of myocardial infarction of little value [5] 5) serum BNP does not improve Canadian Syncope Risk Score [59] 6) urine toxicology * severe anemia = high short-term risk [5] Special laboratory: 1) as indicated by history & physical examination [16] 2) electrocardiogram a) 12-lead EKG, all patients [16,44,50] b) signal averaged ECG (SAECG) may help predict the occurrence of ventricular tachycardia c) most patients (75%) with cardiac cause of syncope have abnormal electrocardiogram [23] - non-sustained ventricular tachycardia - bifasicular block - sinus bradycardia (< 50/min) or sinoatrial block - Mobitz type 2 second degree AV block or third degree AV block - prolonged QT interval [5] - Q wave [62] - ST segment elevation, ST segment depression - T wave changes - supraventricular tachycardia - atrial fibrillation - multiform premature ventricular complexes 3) echocardiography - suspected structural heart disease - valvular heart disease - aortic stenosis 4) exercise tolerance testing (ETT) a) suspected ischemic heart disease b) syncope during or immediately after exercise 5) head-up tilt table test: a) useful in patients with LVEF > 40% in whom neurocardiogenic vasopressor dysfunction (NVD) is suspected, in which delayed orthostatic hypotension develops over 15-45 minutes [16] b) recurrent episodes c) suspected cardiac cause [5] 6) ambulatory blood pressure monitoring 7) Holter or event recorder (loop recorder) [5,22] a) generally of low yield - 11% in octagenarians [15] - 20% in patients >= 90 years of age - higher in men & higher with structural heart disease b) not indicated in initial evaluation of syncope c) implantable event recorder is useful for identifying an infrequent arrhythmia when previous 30-day monitoring was not successful [5,21] 8) carotid sinus massage in elderly a) cardiac monitor b) atropine available 9) electrophysiologic testing rarely indicated [5] a) patients suspected of having a tachydysrhythmia b) evidence of structural heart disease 1] previous myocardial infarction 2] bifascicular block on ECG 3] impaired ventricular function c) a normal study indicates low risk for life-threatening cause of syncope 10) electroencephalogram generally of low yield - not indicated in initial evaluation of syncope Radiology: 1) echocardiogram for suspected structural heart disease [44] - not necessary with normal ECG & negative serum troponin I [18,58] - echocardiogram can be ordered independently from ECG if valvular heart disease suspected [16] 2) carotid ultrasound of little value [5,10] 3) vertebrobasilar ultrasound of little value [10] 4) head CT or brain MRI of little value & not recommended in the absence of neurologic signs [5] Differential diagnosis: 1) circulatory (reduced cerebral blood flow) - vasovagal syncope - suggested by posture (standing), provoking factors (pain, procedure), prodrome (diaphoresis, nausea) - carotid sinus hypersensitivity - pressure on the carotid sinus, tight collar, sudden head turning - situation syncope - association with urination (micturition syncope), defecation, swallowing, cough - orthostatic hypotension - post-prandial syncope - cardiopulmonary disease - obstruction to LV outflow - aortic stenosis, hypertrophic cardiomyopathy, pulmonary embolism, pulmomary hypertension - cardiac arrhythmia: - sudden onset, no prodrome - sinus, atrial & AV node dysfunction - ischemic heart disease - beta-blockers, calcium channel blockers & other anti-arrhythmic drugs [5] 2) hypoxia 3) hypoventilation 4) anemia 5) hypoglycemia 6) cerebral a) TIA - brainstem neurologic signs, vertebrobasilar disease, subclavian steal if preceded by upper extremity exercise b) emotional disturbance c) seizure 1] diaphoresis or nausea prior to loss of consciousness suggests syncope rather than seizure 2] post-ictal state suggests seizure rather than syncope 3] information from observers can contribute in differentiating epilepsy from syncope or psychogenic seizures [54] d) diffuse spasm of cerebral arterioles (hypertensive encephalopathy) 7) emotional disturbances a) anxiety b) hysterical seizures c) cataplexy - no loss of consciousness (recollection of event) - sudden loss of muscle strength & muscle tone - provoked by laughter or anticipatory emotion d) sleep attack Complications: - syncope while driving a) neurally mediated syncope was the most common type b) cumulative probability of recurrent syncope driving is 7% during 8 years [13] c) increased risk of motor vehicle accidents requiring hospital treatment (21 vs 12 per 1000 person-years) [33] - supine hypertension may result from treatment [16] - 25% of patients hospitalized with unexplained 1st episode of syncope diagnosed with pulmonary embolism [43] - 13% of patients with other cause of syncope also with PE Management: 1) hospitalization if indicated a) San Francisco Syncope Rule (best studied) b) Boston Syncope Criteria c) EGSYS score d) Canadian syncope risk score [42,61] e) ROSE index [5] f) syncope associated with exercise [16] g) concern for structural heart disease (i.e. valvular heart disease) based on clinical examination [5] h) syncope evaluation units may become standard of care (see SEEDS) i) most patients can be safely managed as outpatients [5,61] j) hospitalization of elderly does not change in the rate of serious adverse events or mortality [55] 2) arrhythmias a) hospitalization with cardiac monitoring is indicated when cardiac syncope is likely [5] b) treat underlying heart disease c) correct metabolic abnormalities d) consider pacemaker or implantable automatic defibrillator e) if < 40 years, recurrent exertional dyspnea, cardiac arrest, or near drowning, genetic testing is indicated f) see specific arrhythmia 3) neurocardiogenic vasopressor dysfunction (NVD) a) general measures - adequate hydration - consider liberalizing salt intake if hypotensive - use caution with changes in postural position - lie down or place head below heart to abort symptoms - obtain orthostatic blood pressures (supine, sitting, standing) - reduce or stop offending medications - antihypertensives (especially diuretics) - compression stockings may reduce risk of vasovagal reaction by preventing pooling of blood in lower extremities [16] - smaller low carbohydrate meals with postprandial hypotension [62] b) pharmacologic therapy - beta-blockers (cardioselective {beta-1} best) - block orthostatic increase in heart rate in patients with diastolic dysfunction - midodrine or fludrocortisone for orthostatic hypotension - pyridostigmine may helpful for supine hypertension & orthostatic hypotension - disopyramide - theophylline - anticholinergic agents - serotonin reuptake inhibitors 4) anemia - consider hospitalization for syncope associated with hematocrit < 30% [5] 5) in elderly - treatment of multiple underlying causes may be indicated [16] - treat presyncope as syncope [52] 6) prognosis [8,9] a) 22% have multiple episodes (78% do NOT) b) cardiac syncope have 2-fold increased risk of death & 3-fold increased risk of myocardial infarction c) idiopathic cases have 32% increased risk of death & 31% increased risk of myocardial infarction d) No increased risk of death with syncope due to vasovagal reactions, orthostasis or drugs e) San Francisco syncope rule predicts serious outcomes [9] - 1.4% of patients San Francisco Syncope Rule-negative will have a 7-day serious outcome [30] f) risk of motor vehicle accident following emergency department visit for syncope is not increased in the following year [64]

Interactions

disease interactions

Related

Boston Syncope Criteria Canadian Syncope Risk Score causes of syncope Evaluation of Guidelines in SYncope Study score (EGSYS score) FAINT score presyncope; near-syncope risk stratification of syncope in the emergency department (ROSE index) San Francisco syncope rule Syncope Evaluation in the Emergency Department Study (SEEDS)

Specific

convulsive syncope heat syncope neurocardiogenic vasopressor dysfunction; neurally-mediated syncope; reflex syncope (NVD) orthostatic syncope situational syncope

General

cardiovascular disease (CVD) loss of consciousness (LOC) sign/symptom

References

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