Syncope Notes

Syncope Overview

Objectives

  • Understand syncope.

  • Recognize differences in syncope between young and old.

  • Recognize the main causes of syncope:

    • Vasovagal response

    • Orthostatic hypotension

    • Cardiac disease

  • How to investigate and diagnose syncope.

  • How to treat the main causes of syncope.

Definition of Syncope

  • Derived from Greek words "Sūn" (together) and "kóptō" (to strike, cut off).

  • Transient loss of consciousness due to global cerebral hypoperfusion.

  • Characterized by rapid onset, short duration, and complete, spontaneous recovery.

Syncope Incidence

  • 40-50% of the population experiences syncope over a lifetime.

Syncope in Young People

  • Over 90% of syncope in young people (<40 years) is vasovagal syncope (VVS).

  • VVS is the common faint.

  • VVS is a reflex, not an illness.

  • Involves the Bezold-Jarisch reflex.

Bezold-Jarisch Reflex

  • Sequence of events:

    1. Decreased blood pressure (BP↓)

    2. Decreased venous return (Venous return ↓)

    3. Decreased end-diastolic volume (End diastolic volume ↓)

    4. Increased heart rate (HR ↑)

    5. Vigorous contraction of empty ventricle

    6. Baroreceptors trigger

    7. Vagus nerve stimulation

    8. Medulla oblongata

    9. Vasovagal reaction: HR ↓, BP ↓

Recognizing VVS - Presyncope

  • Light-headedness

  • Blackout (retinal ischaemia)

  • Yawning

  • Restlessness

  • Strong urge to lie down

  • Rising sensation

  • Intense heat

  • Nausea

  • Fatigue

  • Older people:

    • Very short, or even absent prodrome

    • Non-specific symptoms

    • "Just went down"

    • "I must have fallen"

  • Witness observations:

    • White/grey appearance

    • Sweating

VVS - Syncope Phase

  • Loss of consciousness

  • Loss of postural tone

  • Injury

  • Transient

  • Incontinence

  • Myoclonic jerks (more common in young people)

  • Older people:

    • Little/no myoclonus

  • Witness misinterpretations:

    • T-LOC lasting minutes to hours (mistaken for epilepsy)

    • Potential misdiagnosis as epilepsy

    • Rarely, mistaken for death (older people)

VVS - Post-Syncope

  • Spontaneous recovery

  • Fatigue (often profound)

  • Coat hanger headache

  • Older people:

    • Longer recovery

VVS - Triggers

  • Situational syncope:

    • Pain

    • Cough

    • Defecation/micturition

    • Deglutition (swallowing)

    • Gelastic (laughter-induced)

  • Shock/emotion

  • Standing, heat, dehydration, vasodilation (exercise, alcohol, sepsis, drugs)

VVS - Treatment

  • Water (+++)

  • Salt

  • Caffeine (↑/↓)

  • Compression stockings

  • Physical counter maneuvers

  • Trigger avoidance

  • Medication adjustments (stopping or starting medications)

  • Tilt-training

  • Pacemaker (in rare cases)

Syncope - Other Causes

  1. VVS

  2. Situational syncope

  3. Carotid sinus syndrome

Carotid Sinus Syndrome

  • Affects older people

  • Little/no warning

  • Unexplained falls/syncope

  • Facial/head injuries

  • Types:

    • Vasodepressor (↓BP): Treat as VVS

    • Cardio-inhibitory (↓HR): Pacemaker

Syncope - Cardiac Causes

  • Cardiac structural disease

  • Arrhythmia

  • Orthostatic hypotension

  • Neurally mediated syncope

Orthostatic Hypotension (OH)

Pathophysiology of OH

  • Venous pooling

  • ↓ venous return

  • ↓ End-Diastolic Volume (EDV)

  • ↓ Stroke Volume (SV)

  • ↓ Cardiac Output (CO)

  • ↓ Blood Pressure (BP)

  • ↓ Baroreceptor stretch

  • Medulla response: Sympathetic (↑ activity), Parasympathetic (↓ activity)

  • ↑ Heart Rate (HR)

  • Vasoconstriction

  • ↑ Venous return

  • ↑ EDV

  • ↑ BP

  • ↑ CO

Recognizing OH

  • Symptoms just after standing up

  • Worse in the morning

  • Nocturnal diuresis

  • Low volume intake

  • Low cortisol levels

  • Dizziness

  • Falls

  • Non-specific low BP symptoms

  • Aggravating factors:

    • Meals

    • Alcohol

    • Medications

    • Illness

    • Dehydration/heat

OH - Treatment

  • Water (+++)

  • Caffeine (↑/↓)

  • Compression stockings

  • Physical counter maneuvers

  • Trigger avoidance

  • Medication adjustments (stopping or starting medications)

VVS vs. OH

  • VVS: A reflex

  • OH: Abnormal response

Cardiac Syncope - Indicators

  • History of heart disease, especially heart failure

  • Chest pain, shortness of breath (SOB)

  • Palpitations

  • Little/no presyncope

  • Abnormal ECG

  • Family history of sudden cardiac death

  • Cardiac medications

  • Syncope while sitting/supine

ECG Clues

  • First-degree heart block: generally does not cause syncope.

  • Second-degree block - Mobitz 1: 2^{nd} degree block - Mobitz 1 – could cause syncope - further testing required

  • Second-degree AV block - Mobitz 2: causes syncope

  • Third-degree block: causes syncope

Other ECG Clues

  • Brady-arrhythmias:

    • Alternating left & right bundle branch block

    • Bifascicular block (LBBB or RBBB with LAFB)

    • Ventricular fibrillation/Ventricular tachycardia (VF/VT)

    • Bradycardia: HR <40 while awake or <50 while active

    • Sinus pause ≥3 seconds

  • Tachyarrthymias:

    • Supraventricular tachycardia (SVT)

    • Delta waves/pre-excitation

    • Long or short QT

  • Other (rare):

    • Epsilon waves (ARVD)

    • Brugada (T wave changes, RBBB pattern)

Investigations - Summary

  • VVS:

    • Clinical diagnosis

    • Tilt-test in cases of doubt

  • OH:

    • Lying & standing BP

    • Systolic BP (sBP) drop ≥20 mmHg or diastolic BP (dBP) drop ≥10 mmHg

  • Carotid Sinus Syndrome (CSS):

    • Carotid sinus massage (CSM) for 10s (supine then upright)

    • sBP drop >50 mmHg

    • Asystole >3s (>6s if pacemaker present)

  • Cardiogenic syncope:

    • 12 lead ECG

      • Previous ischaemia

      • ‘block’ or bradycardia

      • Tachyarrhythmias

    • External loop recorder

    • Internal loop recorder

Falls vs Syncope

  • When falls are actually syncope…

  • Various risk factors and incidents leading up to falls:

  • Balance, Gait, Culprit medication, Home hazard, Orthostatic hypotension, Vision, Carotid sinus hypersensitivity, Neuropathy, Depression, and Vasovagal are all factors that result in falls.

Falls vs. Syncope - Key Differentiators

Favors Falls:

  • Specifically recalls impact

  • Hand/wrist injury

  • No presyncope

  • Presence of environmental factor (e.g. ice/uneven pavement)

Favors Syncope:

  • "I must have…"

  • Facial injury

  • May or may not recall presyncope

  • Unexplained

Important Points - Older People

  • Less pre-syncope/warning

  • Often present with falls not syncope

  • Carotid sinus syndrome affects >40 year olds

  • Higher risk of cardiac causes

Important Points - VVS

  • Syncope: transient, global, rapid, spontaneous

  • Reflex not disease

  • VVS – really common

  • Non-drug treatments are important