Syncope and Presyncope

Syncope & Presyncope: Basics - Faint Facts First

• Syncope: Transient loss of consciousness (TLOC) due to global cerebral hypoperfusion.
  • Key features: Rapid onset, short duration (usually <20 sec), spontaneous, complete recovery.
  • Associated with loss of postural tone.
• Presyncope (Near-syncope): Sensation of impending LOC without actual loss; a prodrome.
  • Symptoms: Lightheadedness, dizziness, weakness, blurred vision, diaphoresis, nausea.
• Core Pathophysiology: Sudden, transient reduction in cerebral blood flow (CBF).
  • Critical ↓: CBF cessation for 6-8 seconds or mean arterial pressure (MAP) falling to 50-60 mmHg at brain level.

⭐ Vasovagal syncope (neurally mediated syncope) is the most common cause of syncope overall, often precipitated by emotional distress, pain, or prolonged standing (orthostatic stress).

Syncope: Etiology & Types - Dizzy Detectives

Syncope: Transient loss of consciousness (T-LOC) from global cerebral hypoperfusion; characterized by rapid onset, short duration, and spontaneous, complete recovery.

📌 Mnemonic: ROCS (Reflex, Orthostatic, Cardiac)

• Reflex (NMS): Most frequent.
  • Vasovagal: Emotional/orthostatic stress; prodrome (nausea, warmth).
  • Situational: Specific triggers (cough, micturition, post-prandial).
  • Carotid Sinus Syncope: Older patients; neck pressure/movement.
• Orthostatic Hypotension (OH):
  • Triggered by standing from supine/sitting.
  • Causes: Drugs (α-blockers, diuretics), volume depletion, autonomic failure (e.g., Diabetes, Parkinson's).
• Cardiac Syncope: Highest risk.
  • Arrhythmic: Brady (e.g., AV block) or Tachy (e.g., VT).
  • Structural/Obstructive: Aortic stenosis, HOCM, PE, MI.

⭐ Adams-Stokes attacks: Syncope due to sudden complete heart block or ventricular tachyarrhythmia, often without warning.

Syncope: Evaluation - Syncope Sleuthing

• Goal: Identify cause and risk stratify.
• Key Evaluation Steps:
  • History: Prodrome, triggers, witness account, medications, FamHx SCD.
  • Physical Exam: Orthostatics (SBP ↓≥20 mmHg or DBP ↓≥10 mmHg), cardiac murmurs, neuro signs.
  • ECG (12-lead): Mandatory. Check arrhythmias, ischemia, structural clues, channelopathies (Brugada, Long QT).

⭐ > A 12-lead ECG is recommended for the initial evaluation of ALL patients presenting with syncope.

Syncope: Risk & Management - Danger & Direction

• High-Risk Markers (⚠️ Admit):

  • Age >60; Known Structural Heart Disease (SHD)/Ischemic Heart Disease (IHD)
  • Exertional/supine syncope; Family Hx of Sudden Cardiac Death (SCD)
  • Abnormal ECG: Ischemia, arrhythmias (Ventricular Tachycardia, severe bradycardia), conduction blocks (Mobitz II, Complete Heart Block, new LBBB/Bifascicular block), Brugada pattern, Long QT/Short QT Syndrome
  • Preceding chest pain/palpitations
  • Severe anemia (Hb <9 g/dL); Systolic BP <90 mmHg

• Management Outline:

  • High-Risk: Hospitalize. Continuous ECG monitoring, urgent Echocardiogram. Consider Holter, Tilt Table Test (TTT), Electrophysiology (EP) study.
  • Low-Risk (Vasovagal/Situational): Reassure, educate on triggers & counter-maneuvers (e.g., leg crossing, handgrip).
  • Specific Rx: Address underlying cause (e.g., pacemaker for symptomatic bradyarrhythmias, ICD for malignant ventricular arrhythmias, drug adjustment).

⭐ Syncope in the presence of bifascicular block (e.g., RBBB + LAFB or LPFB) on ECG strongly suggests intermittent complete heart block and often necessitates pacemaker implantation due to high risk of progression and SCD.

High‑Yield Points - ⚡ Biggest Takeaways

• Syncope: Transient loss of consciousness (TLOC) from global cerebral hypoperfusion; rapid onset, spontaneous recovery.
• Vasovagal syncope: Most common; often preceded by prodrome (nausea, diaphoresis) and specific triggers.
• Cardiac syncope: Most serious; suspect with exertion, palpitations, abnormal ECG, family Hx of SCD.
• Orthostatic hypotension: SBP ↓ ≥20 mmHg or DBP ↓ ≥10 mmHg within 3 min standing.
• 12-lead ECG: Mandatory for all; screens for cardiac causes like arrhythmias or structural disease.