Syncope
Syncope is a neurobehavioral manifestation that is a "transient loss of consciousness and postural tone caused by diminished blood flow to the brain (i.e., brain ischemia). Presyncope refers to the sensation of lightheadedness and loss of strength that precedes a syncopal event or accompanies an incomplete syncope."[1]
Etiology/cause
About 25% of patients have a cardiac cause, 15% are vasovagal and 10% are due to orthostasis.[2][3] About 3% are from myocardial infarction, 91% having normal ST-segments.[4]
2% have a cerebrovascular cause.[2] Generally, this is consider when there is basilar artery or bilateral vertebral or bilateral carotid stenoses severe stenoses. However, there are case reports suggesting unilateral carotid stenoses can cause syncope.[5] However, it is not clear if these patients also had focal neurological symptoms.
2% are due to seizures.[2]
Vasovagal syncope (also called neurocardiogenic syncope, neurogenic syncope, or vasodepressor syncope is the cause of syncope in about 15% of patients.[2] Vasovagal syncope is "loss of consciousness due to a reduction in blood pressure that is associated with an increase in vagal tone and peripheral vasodilation".[6] Vasovagal syncope includes vasodepressor syncope which is syncope during fright or stress.
Some authors use neurocardiogenic syncope or neurally mediated syncope as the broad term, and within this category are the parasympathetic mediated syncopes: 1) vasovagal syncope (syncope during fright or stress), 2) situational syncope (syncope following cough, micturition, or defecation), and 3) carotid sinus syncope (also called carotid sinus hypersensitivity).[7]
Diagnosis
Clinical practice guidelines are available to guide diagnosis.[8]
History and physical
An evaluation based on the initial history and physical examination will correctly diagnose the underlying cause in 63% of patients according to one case series.[9] Interviewing witnesses must be carefully done.[10] Allowing observers to answer "I do not know" may be important.[10]
"Palpitations before syncope, syncope during effort or in supine position, absence of autonomic prodromes and absence of predisposing and/or precipitating factors were found to be predictors of cardiac syncope."[11]
Having no warning symptoms suggests a cardiac arrhythmia.[12] Having more than one prodrome symptom (e.g. dizzines, nausea) is predictive of vasovagal and psychogenic syncope.[13]
Regarding the physical exam, testing or carotid sinus hypersensitivity may be best done with the patients standing.[14]
Testing
"Abnormal ECG and/or heart disease... found to be predictors of cardiac syncope."[11]
A p-wave longer than 120 ms on electrocardiogram is suggestive of a cardiac arrhythmia.[13]
Evaluation of the vertebral and carotid arteries with transcranial and carotid dopplers is mainly helpful if there are focal neurological findings.[15][16]
A clinical practice guideline by the American College of Physicians recommends "neurologic testing, including electroencephalography, computed tomography, and carotid and transcranial Doppler ultrasonography, should be reserved for patients who have neurologic signs or symptoms or carotid bruits".[17]
Clinical prediction rule
A clinical prediction rule is available to help identify patients with cardiac causes of syncope.[11]
Prognosis
| Cause of syncope | mortality[2] at 1 year |
sudden death[2] at 1 year |
mortality[3] at 5 years |
sudden death[3] at 5 years |
|---|---|---|---|---|
| All cases | 14% | 34% | 14% | |
| Cardiac cause | 30% | 24% | 50% | 33% |
| Noncardiac | 12% | 4% | 30% | 5% |
| Unknown | 6% | 3% | 24% | 9% |
The San Francisco Syncope Rule (online) can predict the chance of serious events within seven days.[18] When internally validated, its sensitivity was 98%.[18] However, indpendent, external validations have yielded sensitivities of 89%[19] and 74%[20].
References
- ↑ Anonymous (2024), Syncope (English). Medical Subject Headings. U.S. National Library of Medicine.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Kapoor WN, Karpf M, Wieand S, Peterson JR, Levey GS (July 1983). "A prospective evaluation and follow-up of patients with syncope". N. Engl. J. Med. 309 (4): 197–204. PMID 6866032. [e]
- ↑ 3.0 3.1 3.2 Kapoor WN (May 1990). "Evaluation and outcome of patients with syncope". Medicine (Baltimore) 69 (3): 160–75. PMID 2189056. [e] [Full text from OVID]
- ↑ McDermott D, Quinn JV, Murphy CE (March 2009). "Acute myocardial infarction in patients with syncope". CJEM 11 (2): 156–60. PMID 19272217. [e]
- ↑ Kashiwazaki D, Kuroda S, Terasaka S, et al (January 2005). "[Carotid occlusive disease presenting with loss of consciousness]" (in Japanese). No Shinkei Geka 33 (1): 29–34. PMID 15678866. [e]
- ↑ Anonymous (2024), Vasovagal syncope (English). Medical Subject Headings. U.S. National Library of Medicine.
- ↑ Mathias CJ, Deguchi K, Schatz I (February 2001). "Observations on recurrent syncope and presyncope in 641 patients". Lancet 357 (9253): 348–53. DOI:10.1016/S0140-6736(00)03642-4. PMID 11210997. Research Blogging.
- ↑ Brignole M, Alboni P, Benditt DG, et al (November 2004). "Guidelines on management (diagnosis and treatment) of syncope-update 2004. Executive Summary". Eur. Heart J. 25 (22): 2054–72. DOI:10.1016/j.ehj.2004.09.004. PMID 15541843. Research Blogging.
- ↑ van Dijk N, Boer KR, Colman N, et al (2008). "High diagnostic yield and accuracy of history, physical examination, and ECG in patients with transient loss of consciousness in FAST: the Fainting Assessment study". J. Cardiovasc. Electrophysiol. 19 (1): 48–55. DOI:10.1111/j.1540-8167.2007.00984.x. PMID 17916139. Research Blogging.
- ↑ 10.0 10.1 Thijs RD, Wagenaar WA, Middelkoop HA, Wieling W, van Dijk JG (November 2008). "Transient loss of consciousness through the eyes of a witness". Neurology 71 (21): 1713–8. DOI:10.1212/01.wnl.0000335165.68893.b0. PMID 19015487. Research Blogging.
- ↑ 11.0 11.1 11.2 Del Rosso A, Ungar A, Maggi R, Giada F, Petix NR, De Santo T, Menozzi C, Brignole M. Clinical predictors of cardiac syncope at initial evaluation in patients referred urgently to a general hospital: the EGSYS score. Heart. 2008 Dec;94(12):1620-6. Epub 2008 Jun 2. PMID: 18519550
- ↑ Krahn AD, Klein GJ, Yee R, Skanes AC (May 2001). "Predictive value of presyncope in patients monitored for assessment of syncope". Am. Heart J. 141 (5): 817–21. DOI:10.1067/mhj.2001.114196. PMID 11320372. Research Blogging.
- ↑ 13.0 13.1 Graf D, Schlaepfer J, Gollut E, et al (2008). "Predictive models of syncope causes in an outpatient clinic". Int. J. Cardiol. 123 (3): 249–56. DOI:10.1016/j.ijcard.2006.12.007. PMID 17397948. Research Blogging.
- ↑ Parry SW, Richardson DA, O'Shea D, Sen B, Kenny RA (2000). "Diagnosis of carotid sinus hypersensitivity in older adults: carotid sinus massage in the upright position is essential". Heart 83 (1): 22–3. PMID 10618329. [e]
- ↑ Schnipper JL, Ackerman RH, Krier JB, Honour M (April 2005). "Diagnostic yield and utility of neurovascular ultrasonography in the evaluation of patients with syncope". Mayo Clin. Proc. 80 (4): 480–8. PMID 15819284. [e]
- ↑ Pires LA, Ganji JR, Jarandila R, Steele R (2001). "Diagnostic patterns and temporal trends in the evaluation of adult patients hospitalized with syncope". Arch. Intern. Med. 161 (15): 1889–95. PMID 11493131. [e]
- ↑ Linzer M, Yang EH, Estes NA, Wang P, Vorperian VR, Kapoor WN (June 1997). "Diagnosing syncope. Part 1: Value of history, physical examination, and electrocardiography. Clinical Efficacy Assessment Project of the American College of Physicians". Ann. Intern. Med. 126 (12): 989–96. PMID 9182479. [e]
- ↑ 18.0 18.1 Quinn J, McDermott D, Stiell I, Kohn M, Wells G (May 2006). "Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes". Ann Emerg Med 47 (5): 448–54. DOI:10.1016/j.annemergmed.2005.11.019. PMID 16631985. Research Blogging.
- ↑ Sun BC, Mangione CM, Merchant G, et al (April 2007). "External validation of the San Francisco Syncope Rule". Ann Emerg Med 49 (4): 420–7, 427.e1–4. DOI:10.1016/j.annemergmed.2006.11.012. PMID 17210201. Research Blogging.
- ↑ Birnbaum A, Esses D, Bijur P, Wollowitz A, Gallagher EJ (February 2008). "Failure to Validate the San Francisco Syncope Rule in an Independent Emergency Department Population". Ann Emerg Med. DOI:10.1016/j.annemergmed.2007.12.007. PMID 18282636. Research Blogging.