Syncope

Michelle Chintanaphol

Background

  • Definition: abrupt, transient loss of consciousness with rapid & spontaneous recovery

Classification

  • Cardiac syncope - can have sudden onset with little or no prodrome
    • Tachyarrhythmias: VT, SVT
    • Brady-arrhythmias: sinus node dysfunction, AV blocks (high grade)
    • Structural: Aortic Stenosis, HCM, cardiac tamponade, congenital anomalies, masses/tumors, ICM or NICM causing low cardiac index
    • Obstruction: Pulmonary embolism, severe pHTN
    • Aortic dissection
  • Noncardiac syncope
    • Orthostatic hypotension
    • Autonomic dysfunction
    • Medication-induced (diuretics, nitrates/CCB/alpha blockers, TCAs)
    • Volume depletion (hemorrhage, dehydration)
    • Vasovagal (stress-mediated with prodromal symptoms)
    • Situational (micturition/defecation/coughing/laughing)
    • Carotid sinus sensitivity syndrome (pause for >3 sec and/or decrease in systolic pressure >50 mmHg after stimulation of carotid sinus)
    • Postural orthostatic tachycardia syndrome
  • Differential diagnosis
    • Seizure, stroke/TIA, subclavian steal, metabolic derangements, Intoxication/withdrawal, hypoglycemia, head trauma/concussion
      • With rare exceptions, these do not result in complete LOC with spontaneous recovery

Evaluation

  • Characteristics associated with cardiac syncope
    • Male, >60, known structural/ischemic heart disease, brief/no prodrome, palpitations, syncope while supine/at rest or during exercise, family hx of SCD/premature death, abnormal exam, abnormal baseline ECG
  • Characteristics associated with noncardiac syncope
    • Younger age, syncope with positional changes, prodrome (nausea, vomiting, warmth), triggers, normal baseline ECG

Workup

  • EKG on all pts with syncope, monitor those who are admitted on telemetry
  • CBC, CMP, troponin, BNP (If cardiac cause suspected), POC glucose, UDS, orthostatic VS
  • TTE and consider stress testing particularly in exertional syncope
  • EEG and neuroimaging if high concern for seizure activity or focal neuro deficit (neuro testing comes at high cost and low diagnostic yield)
  • Consider based on clinical suspicion: A1C, Vitamin B12, iron studies, TSH, free light chains/SPEP/UPEP if concerned for amyloidosis

Management - dependent on suspected cause of syncope

  • Cardiac:
    • If arrhythmia is suspected but not captured on admission, consider discharge with event monitor
    • Monitoring duration should be equal to or greater than the frequency of events (e.g. If the symptoms occur roughly once a month, monitoring duration should be at least a month)
  • Noncardiac
    • Reflex
      • Vasovagal - consider tilt table testing if recurrent or diagnosis not clear
      • Situational - mainly avoiding triggers
      • Carotid sinus syndrome- may require PPM
    • Orthostasis
      • Medication related
        • Appropriate to hold potentially offending medications (diuretics, vasodilators, anti-hypertensives) during evaluation
        • Monitor for worsening supine hypertension, arrhythmias, or heart failure when holding
      • Volume depletion; resuscitate as appropriate and re-measure orthostatic vitals
      • Autonomic dysfunction: see autonomics section
  • Driving: TN law does not require any MD to inform the state of TLOC
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