Overview
This lecture covers the clinical approach to syncope, including its definition, main causes, differentiation from mimics, assessment, and diagnostic strategies.
Definition and Features of Syncope
- Syncope is defined by abrupt, transient loss of consciousness, loss of postural tone, short duration, and spontaneous recovery.
- A prodrome (early symptoms) may include lightheadedness, nausea, sweating, and visual changes.
- Pre-syncope refers to prodromal symptoms without loss of consciousness.
- Syncope, pre-syncope, and isolated transient lightheadedness share similar causes and physiology.
Pathophysiology and Main Mechanisms
- All causes involve transient reduction in brain blood flow due to brief hypotension and/or bradycardia.
- Etiologies are grouped into: reflex, cardiogenic, and orthostatic causes.
Reflex Syncope
- Due to abnormal autonomic response; most mechanisms are not well understood.
- Clinical types: vasovagal (most common), situational (triggered by actions like coughing or urination), and carotid sinus hypersensitivity.
- Vasovagal syncope can be triggered by standing, stress, pain, or medical procedures.
- Carotid sinus hypersensitivity involves excessive response to carotid pressure.
Cardiogenic Syncope
- Caused by heart-related issues: bradyarrhythmias, ventricular tachycardia, mechanical problems (aortic stenosis, hypertrophic cardiomyopathy), or massive pulmonary embolism.
- Typically occurs without clear precipitant or with exertion, often in older patients with cardiac risk factors.
Orthostatic Syncope
- Defined by a sudden drop in blood pressure upon standing (≥20 mmHg systolic or ≥10 mmHg diastolic drop).
- Causes: volume depletion, medications (e.g., alpha blockers, antidepressants), or autonomic failure (e.g., Parkinson’s disease, diabetes, alcoholism).
Syncope Mimics
- Seizure, vertebrobasilar insufficiency, subclavian steal syndrome, medication side effects, alcohol blackout, and psychogenic pseudosyncope can resemble syncope.
- These mimics should be excluded before diagnosing true syncope.
Assessment and Diagnostic Approach
- Key history questions: activity before event, presence of prodrome, injury, duration of unconsciousness, recovery time, and witness reports.
- Syncope usually lasts seconds to <5 minutes; longer unconsciousness suggests other causes.
- Differentiate from seizure by assessing for tonic-clonic movements, incontinence, and duration of post-event confusion.
- Reflex syncope usually has a trigger and prodrome; cardiogenic has fewer warning signs and higher risk.
- All syncope patients require an ECG; further tests based on suspected mechanism.
- Cardiac monitoring options include telemetry, ambulatory ECG, and implantable loop recorders.
Management Principles
- Reflex syncope typically requires no further testing unless events are frequent.
- Cardiogenic syncope mandates thorough cardiac evaluation and monitoring.
- Orthostatic syncope should be managed with hydration, medication review, or evaluation for autonomic dysfunction.
Key Terms & Definitions
- Syncope — Sudden, brief loss of consciousness with spontaneous recovery.
- Prodrome — Warning symptoms preceding syncope.
- Vasovagal Syncope — Fainting from autonomic reflex, often from triggers.
- Orthostatic Hypotension — Blood pressure drop on standing, causing syncope.
- Cardiogenic Syncope — Syncope due to cardiac arrhythmia or structural heart disease.
- Prodrome — Early symptom or set of symptoms indicating approaching event.
- Syncope Mimics — Conditions resembling syncope but with different causes.
Action Items / Next Steps
- Ensure all patients with suspected syncope receive an ECG.
- For suspected cardiogenic syncope, arrange further cardiac evaluation and consider monitoring.
- For orthostatic syncope, assess hydration status and review medications.