Syncope

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Contents 1 More Specific Terms 2 Introduction 3 Etiology 4 Epidemiology 5 Pathology 6 History 7 Clinical-manifestations 8 Laboratory 9 Diagnostic-procedures 10 Radiology 11 Complications 12 Differential-diagnosis 13 Management 14 More General Terms 15 Additional Terms 16 References

More Specific Terms

• neurocardiogenic vasopressor dysfunction (NVD)
• situational syncope

Introduction

• Definition: the 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)
• inadequate vasoconstrictor mechanisms

• neurocardiogenic vasopressor dysfunction ( NVD) accounts for the majority of syncopal episodes in the general population

• vasovagal reaction
• carotid sinus syncope (most common cause in elderly)
• situational syncope

• micturition syncope
• defection syncope
• postprandial syncope
• cough syncope
• heat syncope

• postural hypotension ( orthostasis)
• primary autonomic insufficiency
• sympathectomy, pharmacologic or surgical
• diseases of the CNS & peripheral nervous system

• syncope associated with brainstem neurological signs & symptoms
• posterior circulation vascular disease ( vertebrobasilar system)

• increased bradykinin
• vasodilator agent
• tricyclic antidepressants [16]

• hypovolemia

• blood loss
• Addison's disease
• dehydration
• diuretics

• mechanical reduction of venous return

• Valsalva maneuver
• cough
• micturition
• atrial myxoma, ball valve thrombus

• reduced cardiac output

• obstruction to left ventricular outflow

• aortic stenosis
• hypertrophic subaortic stenosis

• obstruction to pulmonary flow

• pulmonic stenosis
• pulmonary embolus (under-diagnosed) [7]
• pulmonary hypertension

• myocardial infarction with pump failure
• cardiac tamponade

• tachydysrhythmias

• ventricular tachycardia

• ventricular fibrillation
• prolonged QT syndrome
• torsades de pointes
• Brugada syndrome

• atrial fibrillation with rapid ventricular response
• AV nodal re-entry tachycardia
• pre-excitation disorder with atrial fibrillation/ flutter

• bradyarrhythmias

• AV block 2nd & 3rd degree with Stokes-Adams attacks
• ventricular asystole
• sinus bradycardia

• sinoatrial block
• sinus arrest
• sick sinus syndrome

• carotid sinus syndrome (most common cause in elderly)
• glossopharyngeal neuralgia & other painful states
• pharmacutical agents

• beta blockers
• calcium channel blocker
• antiarrhythmic drugs

• vascular anomalies

• dissecting aneurysm
• subclavian steal syndrome

• hypoglycemia [16]
• psychogenic
• idiopathic (40%) [8,12]
• predisposition to syncope in the elderly

• decreased arterial compliance, increased systolic blood pressure, left ventricular hypertrophy ( LVH)
• diastolic dysfunction
• hypotensive response to increased heart rate, volume depletion or loss of atrial contraction

Epidemiology

• Syncope occurs in 30-50% of people at some point in their lives
• 3% of emergency department visits & 1% of hospitalizations are due to syncope
• age > 50, male sex & known structural heart disease favors cardiac versus neurally-mediated syncope

Pathology

• cerebral hypoperfusion
• age-related changes predispose to syncope

• reduced baroreflex increase in heart rate & sympathetic peripheral vascular constriction
• reduced left ventricular compliance may reduce left ventricular filling with increases in heart rate
• changes in endocrine & renal function may predispose to dehydration [16]

History

• obtain history from

• patient
• witnesses
• medical responders to scene of event

• obtain details on:

• circumstances, place, time, posture, duration
• pattern of syncope, if multiple events
• relationship to: fasting, eating, daily activities or routines, associated illnesses, bodily functions, exertion, sleep deprivation
• premonitory symptoms

• palpitations
• nausea
• abdominal discomfort
• pallor
• diaphoresis

• recovery symptoms
• family history
• long QT syndrome
• hypertrophic obstructive cardiomyopathy
• detailed medication history

• over-medication ( generic & brand names)

• vasoactive agents
• arrhythmogenic agents

• recent adjustment of medication doses

• eyewitness accounts of stiff limbs, twitches of all limbs, facial color, drooling, head deviation may be correct 1/2 of the time [11]

Clinical-manifestations

• nausea &/or diaphoresis

• may precede neurocardiogenic syncope
• may accompany ischemic heart disease in older adults

• onset of syncope due to cardiac dysrhythmia is generally abrupt (< 5 seconds of warning)
• transient loss of consciousness
• loss of postural tone

• orthostatics by far the most useful diagnostic test
• identifies etiology of syncope in 15-21% of cases
• affected diagnosis & management in ~25% of cases [12]

• full recovery generally occurs after a short time

• feeling of fatigue many accompany neurocardiogenic syncope
• little to no post-event confusion

• seizures may occur secondary to syncope
• multifocal myoclonus occurs in most patients with syncope

Laboratory

• complete blood count ( CBC) for anemia
• serum chemistries

• renal function tests
• electrolytes
• drug levels of therapeutically monitored drugs

• urine toxicology

Diagnostic-procedures

• electrocardiogram

• 12- lead
• signal averaged ECG ( SAECG) may help predict the occurrence of ventricular tachycardia

• exercise tolerance testing ( ETT)

• suspected ischemic heart disease
• syncope during or immediately after exercise

• head-up tilt table test:

• 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]

• electrophysiologic testing

• patients suspected of having a tachydysrhythmia
• evidence of structural heart disease

• previous myocardial infarction
• bifascicular block on ECG
• impaired ventricular function

• a normal study indicates low risk for life-threatening cause of syncope

• Holter or event recorder

• generally of low yield

• 11% in octagenarians [15]
• 20% in patients >= 90 years of age
• higher in men & higher with structural heart disease

• not indicated in initial evaluation of syncope

• electroencephalogram

• generally of low yield
• not indicated in initial evaluation of syncope

• carotid sinus massage in elderly

• cardiac monitor
• atropine available

Radiology

• echocardiogram for suspected structural heart disease
• carotid & vertebrobasilar ultrasound of little value [10]

Complications

• syncope while driving

• neurally mediated syncope was the most common type
• cumulative probability of recurrent syncope driving is 7% during 8 years [13]

• supine hypertension may result from treatment [16]

Differential-diagnosis

• circulatory (reduced cerebral blood flow)
• hypoxia
• hypoventilation
• anemia
• hypoglycemia
• cerebral

• TIA
• emotional disturbance
• seizure

• diaphoresis or nausea prior to loss of consciousness suggests syncope rather than seizure
• post-ictal state suggests seizure rather than syncope

• diffuse spasm of cerebral arterioles ( hypertensive encephalopathy)

• emotional disturbances

• anxiety
• hysterical seizures

Management

• hospitalization if indicated

• Boston Syncope Criteria
• syncope evaluation units may become standard of care (see SEEDS)

• arrhythmias

• hospitalization with cardiac monitoring is indicated when cardiac syncope is likely [5]
• treat underlying heart disease
• correct metabolic abnormalities
• consider implantable automatic defibrillator
• see specific arrhythmia

• neurocardiogenic vasopressor dysfunction ( NVD)

• general measures

• adequate hydration
• use caution with changes in postural position
• lie down or place head below heart to abort symptoms
• obtain orthostatic blood pressures ( supine, sitting, standing)
• stop offending medications

• antihypertensives (especially diuretics)

• pharmacologic therapy

• beta-blockers (cardioselective { beta-1} best)

• block orthostatic increase in heart rate in patients with diastolic dysfunction

• disopyramide
• theophylline
• anticholinergic agents
• serotonin reuptake inhibitors

• anemia

• consider hosptalization for syncope associated with hematocrit < 30% [5]

• prognosis [8,9]

• 22% have multiple episodes (78% do NOT)
• cardiac syncope have 2-fold increased risk of death & 3-fold increased risk of myocardial infarction
• idiopathic cases have 32% increased risk of death & 31% increased risk of myocardial infarction
• No increased risk of death with syncope due to vasovagal reactions, orthostasis or drugs
• San Francisco syncope rule predicts serious outcomes [9]

More General Terms

• cardiovascular disease (CVD)
• sign/symptom

Additional Terms

• causes of syncope
• San Francisco syncope rule
• Syncope Evaluation in the Emergency Department Study (SEEDS)

References

1. Harrison's Principles of Internal Medicine, 13th ed. Companion Handbook, Isselbacher et al (eds), McGraw-Hill Inc. NY, 1995, pg 27-28
2. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 204-205
3. Chan & Winkle, Diagnostic History & Physical Examination, Current Clinical Strategies Publishing. Laguna Hills, 1996
4. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 82
5. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 15, American College of Physicians, Philadelphia 1998, 2006, 2009
6. Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 38, 100-104
7. Wilk et al, Geriatrics 50:46, 1995
8. Journal Watch 22(20):153, 2002 Soteriades ES et al, N Engl J Med 347:878, 2002 PMID: [1]
9. Journal Watch 24(6):50, 2004 Quinn JV et al, Ann Emerg Med 43:224, 2004 PMID: [2]
10. Journal Watch 25(10):79, 2005 Schnipper JL, Ackerman RH, Krier JB, Honour M. Diagnostic yield and utility of neurovascular ultrasonography in the evaluation of patients with syncope. Mayo Clin Proc. 2005 Apr;80(4):480-8. PMID: [3]
11. Thijs RD et al. Transient loss of consciousness through the eyes of a witness. Neurology 2008 Nov 18; 71:1713. PMID: [4]
12. Mendu ML et al Yield of diagnostic tests in evaluating syncopal episodes in older patients. Arch Intern Med 2009 Jul 27; 169:1299 PMID: [5]
    - Heidenreich PA. Assessing the value of a diagnostic test. Arch Intern Med 2009 Jul 27; 169:1262 PMID: [6]
    - Quinn JV Yield of diagnostic tests in evaluating syncopal episodes in older patients [invited commentary]. Arch Intern Med 2009 Jul 27; 169:1305. PMID: [7]
13. Sorajja D et al Syncope while driving: Clinical characteristics, causes, and prognosis. Circulation 2009 Sep 15; 120:928 PMID: [8]
14. Epstein AE et al Personal and Public Safety Issues Related to Arrhythmias That May Affect Consciousness: Implications for Regulation and Physician Recommendations Circulation. 1996 94:1147-1166 <PubMed> PMID: [9] <Internet> [10]
15. Kuhne M et al. Holter monitoring in syncope: Diagnostic yield in octogenarians. J Am Geriatr Soc 2011 Jul; 59:1293 PMID: [11]
16. Geriatric Review Syllabus, 7th edition Parada JT et al (eds) American Geriatrics Society, 2010
17. Grossman SA et al. Reducing admissions utilizing the Boston Syncope Criteria. J Emerg Med 2012 Mar; 42:345. PMID: [12]
18. NINDS Syncope Information Page [13]
19. National Guideline Clearinghouse
    - Guidelines on management (diagnosis and treatment) of syncope. European Society of Cardiology ngc-guideline: [14]
    - Clinical policy: critical issues in the evaluation and management of adult patients presenting to the emergency department with syncope. American College of Emergency Physicians ngc-guideline: [15]
    - Best evidence statement (BESt). Evaluation of syncope. Cincinnati Children's Hospital Medical Center ngc-guideline: [16]
    - Transient loss of consciousness ('blackouts') management in adults and young people National Clinical Guideline Centre for Acute and Chronic Conditions ngc-guideline: [17]

syncope