Stethopedia | Approach

Approach to

Syncope

Confirm it was syncope, screen for high-risk features that need admission, then sort the cause by mechanism: reflex, orthostatic, or cardiac.

  1. Transient loss of consciousness with full spontaneous recovery
  2. Eyewitness history, orthostatic vitals, 12-lead ECG1,2
  3. Any high-risk feature?

High risk: admit for telemetry and echo1,2

  • Exertional or supine; no prodrome
  • Palpitations or chest pain beforehand
  • Structural heart disease or heart failure
  • Abnormal ECG: block, long QT, Brugada, WPW
  • SBP <90, HR <40 awake, or GI bleeding
  • Family history of young sudden death

If not: which mechanism?

CausesCluesWorkupManagement

Reflex

  • Vasovagal
  • Situational: cough, micturition
  • Carotid sinus hypersensitivity
  • Trigger: standing, pain, emotion
  • Prodrome: warmth, nausea, sweating
  • Normal heart and ECG
  • History alone if typical1
  • Tilt test if recurrent, unclear2
  • Explain; avoid triggers
  • Counter-pressure manoeuvres9
  • Salt and fluids if no hypertension1

Orthostatic

  • Volume loss or bleeding
  • Drugs: diuretics, vasodilators
  • Autonomic failure: PD, diabetes
  • Within 3 min of standing
  • Older; new or changed drugs
  • SBP ↓≥20 or DBP ↓≥10 in 3 min7
  • CBC, creatinine; drug review
  • Stop culprit drugs; give volume
  • Compression; rise slowly
  • Midodrine or fludrocortisone1

Arrhythmia

  • VT/VF: scar, long QT, Brugada
  • High-grade AV block
  • SVT, WPW, sinus node disease
  • Abrupt, no prodrome; supine
  • Palpitations; family sudden death
  • First event at ≥35 y (LR 3.3)5
  • Telemetry if high risk
  • Holter, patch or loop recorder1
  • EP study in selected cases2
  • Pacemaker for AV block1
  • ICD or ablation for VT1
  • Stop QT-prolonging drugs; fix K, Mg

Structural

  • Aortic stenosis, HCM
  • Pulmonary embolism
  • MI, tamponade, dissection
  • Syncope on exertion; murmur
  • Chest pain, dyspnea, hypoxemia
  • Echo if heart disease suspected1
  • Troponin; CTPA if PE likely8
  • Treat cause: AVR, anticoagulation, PCI
  • Avoid vasodilators in AS or HCM

Mimics

  • Seizure
  • Hypoglycemia, intoxication
  • TIA, psychogenic
  • Tongue bite, postictal state6
  • Focal deficit; LOC >5 min
  • Glucose; EEG if seizure likely
  • CT or MRI if focal signs
  • Treat cause; neurology referral

Can't-miss cause Superscripts link to the references below.

References

  1. Shen WK, Sheldon RS, Benditt DG, et al. 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope. J Am Coll Cardiol. 2017;70:e39–e110. PubMed 28286221
  2. Brignole M, Moya A, de Lange FJ, et al. 2018 ESC guidelines for the diagnosis and management of syncope. Eur Heart J. 2018;39:1883–1948. PubMed 29562304
  3. Thiruganasambandamoorthy V, Kwong K, Wells GA, et al. Development of the Canadian Syncope Risk Score to predict serious adverse events after emergency department assessment of syncope. CMAJ. 2016;188:E289–E298. PubMed 27378464
  4. Thiruganasambandamoorthy V, Sivilotti MLA, Le Sage N, et al. Multicenter emergency department validation of the Canadian Syncope Risk Score. JAMA Intern Med. 2020;180:737–744. PubMed 32202605
  5. Albassam OT, Redelmeier RJ, Shadowitz S, et al. Did this patient have cardiac syncope? The Rational Clinical Examination systematic review. JAMA. 2019;321:2448–2457. PubMed 31237649
  6. Sheldon R, Rose S, Ritchie D, et al. Historical criteria that distinguish syncope from seizures. J Am Coll Cardiol. 2002;40:142–148. PubMed 12103268
  7. Freeman R, Wieling W, Axelrod FB, et al. Consensus statement on the definition of orthostatic hypotension, neurally mediated syncope and the postural tachycardia syndrome. Clin Auton Res. 2011;21:69–72. PubMed 21431947
  8. Costantino G, Ruwald MH, Quinn J, et al. Prevalence of pulmonary embolism in patients with syncope. JAMA Intern Med. 2018;178:356–362. PubMed 29379959
  9. van Dijk N, Quartieri F, Blanc JJ, et al. Effectiveness of physical counterpressure maneuvers in preventing vasovagal syncope: the Physical Counterpressure Manoeuvres Trial (PC-Trial). J Am Coll Cardiol. 2006;48:1652–1657. PubMed 17045903
  10. Gay E, Levy N, eds. Syncope. In: Department of Medicine Housestaff Manual, 30th ed. 2024:34.

For education only; not a substitute for clinical judgment or local protocols. Where sources differ, the flowchart follows the current guideline.

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