Syncope & Presyncope

Syncope

Sudden, transient loss of consciousness (LOC) characterized by loss of postural tone, leading to a brief period of unconsciousness. It resolves spontaneously and completely without the need for intervention.

 

Presyncope

Sensation of impending syncope without actual loss of consciousness.

 

Both presentations share similar rates of adverse outcomes and thus require comparable evaluation strategies.

 

 

Classification of Syncope

A. Cardiac Syncope

i. Arrhythmias:

• Includes tachyarrhythmias (e.g., ventricular tachycardia) and bradyarrhythmias (e.g., complete heart block).

ii. Myocardial Infarction (MI):

• Acute coronary syndromes can lead to syncope.

iii. Structural Cardiac Abnormalities:

• Such as hypertrophic obstructive cardiomyopathy (HOCM) or aortic stenosis (AS).

 

B. Neurally Mediated (Reflex) Syncope

i. Vasovagal Syncope:

• Triggered by factors like emotional stress or prolonged standing.

ii. Situational Syncope:

• Occurs during specific activities such as micturition or defecation.

iii. Carotid Sinus Hypersensitivity:

• Triggered by pressure on the carotid sinus (e.g., tight collars).

 

C. Orthostatic Syncope

i. Volume Depletion:

• Due to dehydration, hemorrhage, or diuretic use.

ii. Postural Tachycardia Syndrome (POTS):

• Characterized by excessive heart rate increase upon standing.

iii. Drug-Induced:

• Medications affecting autonomic tone or blood pressure.

iv. Autonomic Failure:

• Conditions like Parkinson's disease affecting autonomic regulation.

 

1. Evaluation in the Emergency Department

When assessing a patient presenting with syncope or presyncope, the primary objectives are to determine:

i. Is the condition life-threatening?

ii. Is the patient at high or low risk for adverse outcomes?

iii. Should the patient be admitted for observation or safely discharged?
 

A. Targeted & Detailed History Taking

Trigger Events Prior to Syncope:

• Cardiac etiology: Exertional or sudden onset.
• Orthostatic syncope: Related to postural changes.
• Carotid sinus hypersensitivity: Shaving, tight collar, turning head. 
• Vasovagal syncope: Strong physical or emotional stress, prolonged standing, micturition, defecation, swallowing, coughing. 

 

Associated Symptoms:

• Chest Pain, Palpitations, Shortness of Breath (SOB): May indicate acute coronary syndrome (ACS) or pulmonary embolism (PE).
• Abdominal or Lower Back Pain: Suggestive of a dissecting abdominal aortic aneurysm (AAA).
• Prodromal Symptoms: Often seen in vasovagal syncope.
• Headache: Could indicate subarachnoid hemorrhage (SAH).

 

Additional History Elements:

• Duration of Loss of Consciousness?
• Was the Event Witnessed?
• Prior Episodes: Multiple or recent episodes increase concern.
• Family History: Unexplained sudden death or early cardiovascular disease (<50 years old).
• Medication Use: Assess for drug-induced causes.

 

Differentiation from Seizures:

Features Suggestive of Seizure:

• Eye/head deviation
• Tongue biting
• Post-ictal drowsiness
• Tonic/clonic movements witnessed.

 

 

B. Diagnostic Evaluation

i. Electrocardiogram (ECG): Essential for identifying arrhythmias and other cardiac abnormalities.

Key ECG Findings: Look for W.O.B.B.L.E.R

Wolff-Parkinson-White (WPW) Syndrome: Short PR interval, delta wave.

Obstructed AV Nodal pathway: Second or third-degree heart block.

Bifascicular Block

Brugada Syndrome

Left Ventricular Hypertrophy (consider AS, HOCM)

Epsilon Wave (Arrhythmogenic Right Ventricular Dysplasia - ARVD),

Repolarization Abnormalities (prolonged/shortened QT).
 

ii. Laboratory Tests

• FBC, Electrolytes: To identify metabolic causes.
• Troponin: If ACS are suspected.

 

iii. Bedside Echocardiogram (ECHO):

• Assess structural cardiac abnormalities.

iv. Blood Pressure Measurements (lying and standing):

• To evaluate for orthostatic hypotension.

 

2. Risk Stratification

Risk Assessment Tools:

i. San Francisco Syncope Rule:

• C: Congestive Heart Failure
• H: Hematocrit < 30%
• E: ECG abnormalities
• S: Shortness of breath
• S: Systolic BP < 90 mmHg

 

ii. Canadian Syncope Risk Score:

Risk Factor Score Predisposition to vasovagal syncope -1 History of heart disease +1 Systolic BP < 90 mmHg or > 180 mmHg +2 Elevated troponin +2 Abnormal ECG +2 Complaint of shortness of breath +2 Syncope in the supine position or during exertion +2

Risk Score Interpretation

• Low Risk: Score ≤ 0
• Intermediate Risk: Score 1-3
• High Risk: Score ≥ 4

 

Risk Categories:
 

Medium or High Risk:

• Patients should be admitted for observation and further workup.

Low Risk:

• Patients may be safely discharged with appropriate reassurance and outpatient follow-up.

 

References
1. Varela, M., Camargo, C. A., & Adams, M. R. (2009). Syncope in the Emergency Department. New England Journal of Medicine, 361(9), 858-867. DOI:10.1056/NEJMra0806751
2. Carre, F., Dong, W. K., & Côté, M. (2016). Canadian Syncope Risk Score: A multicentre prospective study of outcomes and predictors of short-term adverse events after emergency department syncope. BMJ, 352, h5627. DOI:10.1136/bmj.h5627
3. Freeman, R., Clesham, S., Haig, D., et al. (2016). European Society of Cardiology Guidelines for the diagnosis and management of syncope. European Heart Journal, 37(29), 2315-2381. DOI:10.1093/eurheartj/ehw128
4. Anderson, J. L., Thompson, B. T., Forman, J. P., et al. (2010). The San Francisco Syncope Rule: A Prospective Study of Validation and Refinement. Annals of Emergency Medicine, 55(5), 435-444.e3. DOI:10.1016/j.annemergmed.2010.01.021