• Sudden transient loss of consciousness due to cerebral hypoperfusion

Etiologies {nejm 2002.347 878; jacc 2006:47:473)

• Neurocardiogenic (a.k.a. vasovagal. 20%; NijM 2005:3511004): t sympathetic tone —

vigorous contraction of LV — mechanoreceptors in LV trigger t vagal tone (hyperactive Bezold-Jarisch reflex) \ HR (cardioinhibitory) and/or i BP (vasodepressor) related disorders: carotid sinus hypersens. (in 39% of elderly. art/ir*« 2006;166:s15); cough, deglutition, defecation & micturition syncope

• Orthostatic hypotension (10%)

hypovolemia, diuretics, deconditioning vasodilators (especially if combined with 0 chronotropes)

autonomic neuropathy (diabetes. EtOH. amyloid, renal failure. POTS. Shy-Drager)

• Cardiovascular

Arrhythmia (15%)

Bradyarrhythmias: SSS, high-grade AV block. 0 chronotropes. PPM malfunction Tachyarrhythmias: VT. SVT (syncope rare unless structural heart disease or WPW) Mechanical (5%) Endocardial: AS. MS. PS. prosthetic valve thrombosis, myxoma Myocardial: pump dysfxn from Ml or outflow obstruction from HCMP (but usually VT) Pericardial: tamponade

Vascular PE. PHT. aortic dissection, subclavian steal

• Neurologic (10%): seizure (technically not syncope). TIA/CVA. vertebrobasilar insufficiency, migraine

• Miscellaneous (technically not syncope): hypoglycemia, hypoxia, anemia, psychogenic

Workup (etiology cannot be determined in 35% of cases)

• History (from Pt and witnesses if available)

activity and posture before the incident precipitating factors: exertion (AS. HCMP. PHT). positional A (orthostatic hypotension), stressors such as sight of blood, pain, emotional distress, fatigue, prolonged standing, warm environment. NJV. cough/micturition/defecation/swallowing (neurocardiogenic). head turning or shaving (carotid sinus hypersens.); arm exercise (subclavian steal) prodrome (eg. diaphoresis, nausea, blurry vision): cardiac < 5 sec. vasovagal >5 sec associated sx: chest pain. palp., neurologic, post-ictal, bowel or bladder incontinence (convulsive activity for <10 sec may occur with transient cerebral hypoperfusion)

• PMH: prior syncope, previous cardiac or neurologic dis.; no CV disease at baseline -» 5%

cardiac. 25% vasovagal; CV disease — 20% cardiac. 10% vasovagal (nejm 2001347 878)

• Medications vasodilators: «-blockers, nitrates. ACEI/ARB. CCB. hydralazine, phenothiazines, antidep. diuretics; © chronotropes (eg. {J-blockers and CCB)

proarrhythmic or QT prolonging: class IA, IC or III antiarrhythmics, et al. (see "ECG") psychoactive drugs: antipsychotics. TCA. barbiturates, benzodiazepines. EtOH

• Physical exam

VS including orthostatics (supine — standing results in >20 mmHg i SBP. >10 mmHg

I DBP. or >10-20 bpm T HR). BP in both arms cardiac: HF (T JVP. displ. PMI. Si), murmurs. LVH (S*. LV heave). PHT (RV heave. T P2) vascular exam: ✓ for asymmetric pulses, carotid bruits, carotid sinus massage neurologic exam: focal findings, evidence of tongue biting; fecal occult blood test

• ECG (abnormal in 50%. definitively identifies cause of syncope in 10%)

sinus bradycardia, sinus pauses. AVB. BBB. SVT. VT

ischemic changes (new or old); atrial or ventricular hypertrophy markers of arrhythmia: ectopy, t QT. preexcitation. Brugada pattern, e wave (ARVD)

Other diagnostic studies (consider ordering based on results of H&P and ECG)

• Ambulatory ECG monitoring: if suspect arrhythmogenic syncope

Holter monitoring (continuous ECG 24-48 h): useful if frequent events arrhythmia • sx (4%); asx but signif. arrhythmia (13%); sx but no arrhythmia 07%) Event recorder (activated by Pt to record rhythm strip): useful for infrequent events, but problematic if no prodrome; yield 20-50% over 30-60 d of monitoring Loop recorders (continuously save rhythm strip and .. can be activated after an event): useful for infrequent events including those w/o prodrome

Implantable loop recorders (inserted SC; can record for up to 14 mos): useful for very infrequent events; yield 90% after 1 y (Ajc 2003:92:1231) I • Echocardiogram: r/o structural heart disease

• ETT: esp. wI exertional syncope; r/o ischemia- or catecholamine-induced arrhythmias

• Cardiac catheterization: consider if noninvasive tests suggest ischemia

• Electrophysiologic studies (EPS)

consider if arrhythmia detected, if structural heart disease, or if CAD (esp. with low EF) 50% abnl (inducible VT. conduction abnormalities) if heart disease, but ? significance 3-20% abnl if abnl ECG; <1% abnl if normal heart and normal ECG (Annats 1997:127:76)

• Tilt table testing (provocative test for vasovagal syncope): r/o other causes first

• in 50% w/ recurrent unexplained syncope; Se 26-80%, Sp - 90%; reprod. - 80%

• Cardiac MRI: helpful to dx ARVD if suggestive ECG. echo (RV dysfxn). or - FH of SCD

• Neurologic studies (cerebrovascular studies, CT, MRI, EEG): if H&P suggestive; low yield

Figure 1-6 Approach to syncope

Syncope i

History. Physical Exam (incl. orthostatics). 12-lead ECG

diagnostic suggestive negative diagnostic suggestive negative

? tit table if recurs

EEG. cerebrovasc. CT/MRI

? tit table if recurs

EEG. cerebrovasc. CT/MRI

EP study

(Adapted from ¡ACC 2006:47:473)

High-risk features (usually warrant admission with telemetry & further testing)

• Age -60 y. h/o CAD. CMP. valvular disease, congenital heart disease, arrhythmias

• Syncope c/w cardiac cause (lack of prodrome, exertional, resultant trauma)

• Abnormal cardiac exam or ECG


• Arrhythmia, cardiac mechanical, or neurologic syncope: treat underlying disorder

• Vasovagal syncope: ! midodrine. fludrocortisone, disopyramide, anticholin.. theophylline;

i 16 oz of HjO before at-risk situations (Ore 2003:108 2660)

no proven benefit w/ (¿-blockers (Ore 2006;113:1164) or PPM (;ama 2003:2892224)

• Orthostatic syncope: volume replete; if chronic -» rise from supine to standing slowly.

compressive stockings, midodrine. fludrocortisone, high Na diet

Prognosis (Ann £mcrg Med 1997:29:459: NCJM 2002:347:878)

• 22% overall recurrence rate

• Cardiac syncope: 2-fold I in mort.. 20-40% 1-year SCD rate, median survival 6 y

• Unexplained syncope w/ 1.3-fold * in mort. but noncardiac or unexplained syncope w/ nl

ECG. no h/o VT. no HF. age 45 low recurrence rate and <5% 1-year SCD rate

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