Syncope

Syncope is a sudden, completely reversible loss of consciousness secondary to an acute reduction of cerebral perfusion, which may last from several seconds up to minutes. The most frequent form is vasovagal syncope, which is triggered by emotional stress or prolonged standing, and may be diagnosed with the tilt table test. Orthostatic syncope may occur upon suddenly standing up after prolonged sitting or lying down. It is caused by a drop in blood pressure. This relatively benign cause may, however, lead to life-threatening injuries as a result of falls. A thorough medical investigation is necessary as syncopes may also be the result of a serious cardiovascular disorder (e.g., cardiac arrhythmia or valvular stenosis). The treatment strategy is dependent on the cause of the syncopes.

• TLOC (transient loss of consciousness): temporary syncope of unknown origin

References:^{[1][2][3][4][5][6][7][8]}

• Prodrome: presyncope
  • Vasovagal: impairment of senses; , nausea, pallor, warmth, diaphoresis, lightheadedness, and hyperventilation
  • Orthostatic: lightheadedness, nausea, and dizziness
  • Cardiac: no prodrome; often sudden fall
• Rapid onset loss of consciousness
  • Accompanied by complete loss of muscle tone
  • Last seconds to minutes followed by spontaneous recovery
  • Convulsive syncope: common form in which loss of consciousness is accompanied by myoclonic movements

Thorough neurological and cardiopulmonary assessments, including pulse and blood pressure measurement in the supine, standing, and sitting positions, are crucial for identifying the underlying etiology!
References:^[3][5]

• Patient history: Determine triggers; , ask witnesses how patient behaved during event, and medication/medical/family history.
• Routine investigations
  • ECG (for all patients!)
  • CBC (↓ serum Hb)
• Additional tests
  • Cardiac origin suspected (see also cardiac arrhythmia)
    • Cardiac monitoring (If ECG is not diagnostic and a cardiac cause is strongly suspected): sinus bradycardia < 40/min, sinus pauses > 3 seconds, atrioventricular (AV) or bundle branch blocks
    • Stress ECG (ischemia)
    • Echocardiography: if structural heart disease is suspected or ECG is abnormal
    • Cardiac enzymes
    • Carotid ultrasound with doppler
  • Pulmonary origin suspected : chest x-ray (suspected pneumonia, lung mass) and ventilation/perfusion scanning (suspected pulmonary embolus)
  • Neurological origin suspected : head imaging (CT, MRI, or MRA showing ischemia or hemorrhage) and EEG (seizure)
  • Other laboratory tests: : abnormal electrolytes, abnormal urinalysis ↑ BUN/creatinine ratio (assess for signs of hypovolemia in orthostatic hypotension), stool occult blood test
  • Maneuvers
    • Testing for orthostatic hypotension or vasodepressor syncope
      • Patient is asked to stand after being in supine position for at least 5 minutes → Blood pressure is measured each minute for at least 3 minutes.
      • If systolic BP decreases by ≥ 20 mm Hg and the diastolic BP decreases by ≥ 10 mm Hg, or BP < 90 mm Hg → orthostatic hypotension
      • Coinciding bradycardia → vasodepressor syncope
    • Tilt table test
      • Determines if vasovagal or orthostatic syncope is present
      • Procedure
        • The patient is strapped onto a tilt table in a supine position for 15 minutes, and then is raised passively to an angle of around 70°.
        • Positive: reflex hypotension (systolic blood pressure < 90 mm Hg) and bradycardia (vasovagal) or slow progressive hypotension (orthostatic) with presyncope or syncope
        • Negative (normal): increased heart rate along with barely changed blood pressure and no clinical signs of syncope or presyncope

It is important to rule out life-threatening causes of syncope such as pulmonary embolism, hemorrhage, or serious cardiac conditions!
References:^{[2][3][5][9][10][11]}

References:^[5][12]

The differential diagnoses listed here are not exhaustive.

• Treat underlying condition
  • Arrhythmogenic syncopes may require a pacemaker; or treatment with antiarrhythmic drugs.
  • Patients with carotid sinus syndrome should be advised to avoid tight collars and remain hydrated.
• Vasovagal syncopes
  • Physiological counterstrategies: Crossing the legs, tensing muscles, lying down, and elevating the legs can reverse the syncope.
  • Avoid triggers
• Orthostatic syncopes
  • Sufficient intake of sodium and fluids
  • Compression stockings
  • Adjust medications (e.g., diuretics)
  • Fludrocortisone if unable to manage episodes with nonpharmacological interventions

References:^[5]

• Depends on the underlying condition
• Cardiac syncope is associated with one-year mortality rates of up to 33%.
• Fall injuries

References:^[5]

We list the most important complications. The selection is not exhaustive.

1. Herold G. Internal Medicine. Herold G ; 2014
2. Agabegi SS, Agabegi ED. Step-Up To Medicine. Wolters Kluwer Health ; 2015
3. Benditt D. Syncope in adults: Clinical manifestations and diagnostic evaluation. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/syncope-in-adults-clinical-manifestations-and-diagnostic-evaluation.Last updated: October 12, 2016. Accessed: February 17, 2017.
4. Prandoni P, Lensing AWA, Prins MH, et al. Prevalence of Pulmonary Embolism among Patients Hospitalized for Syncope. N Engl J Med. 2016; 375 : p.1524-1531. doi: 10.1056/NEJMoa1602172 . | Open in Read by QxMD
5. Morag R. Syncope. Syncope. New York, NY: WebMD. http://emedicine.medscape.com/article/811669. Updated: January 13, 2017. Accessed: March 15, 2017.
6. Chen-Scarabelli C, Scarabelli TM. Neurocardiogenic syncope. BMJ. 2004; 329 (7461): p.336-341. doi: 10.1136/bmj.329.7461.336 . | Open in Read by QxMD
7. O’Mahony D. Pathophysiology of carotid sinus hypersensitivity in elderly patients. Lancet. 1995; 346 (8980): p.950-952. doi: 10.1016/s0140-6736(95)91563-x . | Open in Read by QxMD
8. Kaufmann H, Freeman R. Postural Tachycardia Syndrome. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/postural-tachycardia-syndrome.Last updated: March 3, 2015. Accessed: March 2, 2018.
9. Bradley JG, Davis KA. Orthostatic hypotension. Am Fam Physician. 2003; 68 (12): p.2393-2399.
10. Juraschek SP, Miller ER, Appel LJ. Orthostatic hypotension and symptoms in the AASK Trial. Am J Hypertens. 2018 . doi: 10.1093/ajh/hpy010 . | Open in Read by QxMD
11. Benditt D. Upright Tilt Table Testing in the Evaluation of Syncope. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/upright-tilt-table-testing-in-the-evaluation-of-syncope.Last updated: August 10, 2017. Accessed: March 2, 2018.
12. Lima Neto A, Bittar R, Gattas G, et al. Pathophysiology and diagnosis of vertebrobasilar insufficiency: A review of the literature. Int Arch Otorhinolaryngol. 2016; 21 (3): p.302-307. doi: 10.1055/s-0036-1593448 . | Open in Read by QxMD
13. Olshansky B. Reflex syncope. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/reflex-syncope.Last updated: August 14, 2014. Accessed: February 17, 2017.
14. Runser LA, Gauer RL, Houser A. Syncope: Evaluation and Differential Diagnosis.. Am Fam Physician. 2017; 95 (5): p.303-312.
15. Mellusi J. Differential diagnosis of syncope.. Anesth Prog. 1967; 14 (1): p.4-11.
16. Stern SDC, Cifu AS, Altkorn D. Symptom to Diagnosis An Evidence Based Guide, Fourth Edition. McGraw-Hill Education / Medical ; 2019