Syncope And Pre Syncope

Introduction

Syncope and pre-syncope are common presentations in Canadian emergency departments and primary care settings. As a future Canadian physician preparing for the MCCQE1, understanding these conditions is crucial for providing effective patient care and excelling in your exam.

Epidemiology in the Canadian Context

• Syncope accounts for approximately 1-3% of emergency department visits in Canada
• Annual incidence: 6.2 per 1000 person-years in the general Canadian population
• Prevalence increases with age, particularly in individuals over 70 years

Pathophysiology

Understanding the pathophysiology is crucial for MCCQE1 preparation:

1. Cerebral Hypoperfusion: Syncope occurs when cerebral blood flow decreases by approximately 35% or more
2. Systemic Hypotension: Often the underlying cause of reduced cerebral perfusion
3. Autonomic Dysfunction: Can lead to inappropriate vasodilation or bradycardia

Classification and Etiology

Clinical Presentation and Diagnosis

Canadian Guidelines for Syncope Management

The Canadian Cardiovascular Society (CCS) provides specific guidelines for syncope management:

1. Risk stratification using the Canadian Syncope Risk Score (CSRS)
2. Emphasis on initial evaluation in the emergency department
3. Recommendations for admission and outpatient management

Treatment and Management

Treatment depends on the underlying cause:

1. Reflex Syncope:

   • Patient education
   • Physical counterpressure maneuvers
   • Increased fluid and salt intake
   • Pharmacological therapy (e.g., midodrine) in refractory cases

2. Orthostatic Syncope:

   • Address underlying cause (e.g., medication adjustment, volume repletion)
   • Compression stockings
   • Pharmacological therapy (e.g., fludrocortisone)

3. Cardiac Syncope:

   • Treat underlying arrhythmia or structural heart disease
   • Pacemaker or implantable cardioverter-defibrillator (ICD) if indicated

Key Points to Remember for MCCQE1

• Always consider life-threatening causes of syncope (e.g., cardiac arrhythmias, pulmonary embolism)
• ECG is mandatory in all syncope evaluations
• Use the Canadian Syncope Risk Score for risk stratification
• Distinguish syncope from seizures, vertigo, and other causes of transient loss of consciousness
• Recognize red flags: syncope during exertion, family history of sudden cardiac death, abnormal ECG findings

MCCQE1 Mnemonics

Remember the causes of syncope with "LOC":

• L: Low blood pressure (orthostatic, medications)
• O: Outflow obstruction (aortic stenosis, hypertrophic cardiomyopathy)
• C: Cardiac (arrhythmias, structural heart disease)

Sample Question

A 68-year-old woman presents to the emergency department after a syncopal episode while standing in line at the grocery store. She reports feeling lightheaded and nauseated before losing consciousness. The episode lasted about 30 seconds, and she recovered spontaneously. She has a history of hypertension and takes hydrochlorothiazide. Her vital signs are: BP 110/70 mmHg, HR 72 bpm, RR 16/min, O2 Sat 98% on room air. Which one of the following is the most appropriate next step in management?

• A. Admit for continuous cardiac monitoring
• B. Order a head CT scan
• C. Perform orthostatic vital signs
• D. Start intravenous fluids
• E. Consult neurology for possible seizure

Explanation

The correct answer is:

• C. Perform orthostatic vital signs

Explanation: This patient's presentation is suggestive of orthostatic syncope, given her age, use of a diuretic (hydrochlorothiazide), and the circumstances of the event (standing in line). The most appropriate next step is to perform orthostatic vital signs to evaluate for orthostatic hypotension. This non-invasive test can provide valuable diagnostic information and guide further management.

• Option A is not appropriate as there are no clear indications for admission based on the information provided.
• Option B (head CT) is not indicated in uncomplicated syncope without focal neurological symptoms.
• Option D (IV fluids) may be considered if orthostatic hypotension is confirmed, but it's premature at this stage.
• Option E (neurology consult) is not necessary as the presentation is not suggestive of a seizure.

This question tests the candidate's ability to prioritize appropriate investigations in syncope, aligning with the MCCQE1 objectives of clinical decision-making and resource stewardship in the Canadian healthcare system.

References

1. Sheldon RS, Raj SR, Duff HJ, et al. Canadian Cardiovascular Society Guidelines for the Diagnosis and Management of Syncope. Can J Cardiol. 2022;38(8):1047-1089. doi:10.1016/j.cjca.2022.04.019

2. 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(12):E289-E298. doi:10.1503/cmaj.151469

3. Brignole M, Moya A, de Lange FJ, et al. 2018 ESC Guidelines for the diagnosis and management of syncope. Eur Heart J. 2018;39(21):1883-1948. doi:10.1093/eurheartj/ehy037

4. 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(5):e39-e110. doi:10.1016/j.jacc.2017.03.003

5. Runser LA, Gauer RL, Houser A. Syncope: Evaluation and Differential Diagnosis. Am Fam Physician. 2017;95(5):303-312.