264.2 📚 國考版

264.2.0.1 必背 — SVT Types

Type	Mechanism	Key Features
AVNRT	Slow + fast pathway re-entry in AV node	Most common (~ 60%); narrow regular; pseudo-S in II, III, aVF / pseudo-R’ in V1
AVRT (WPW)	Accessory pathway re-entry (Kent bundle)	Orthodromic narrow / antidromic wide; WPW pre-excitation baseline
Atrial flutter	Macro re-entry in atria	Saw-tooth pattern; 2:1 → rate 150
Atrial tachycardia	Focal automaticity	P morphology different from sinus; multifocal AT (COPD)
Junctional	AV junction focus	AV dissociation possible; digoxin toxicity

264.2.0.2 必背 — Acute Stable Management

1. Vagal maneuvers (modified Valsalva — REVERT trial; carotid massage if no bruit)
2. Adenosine 6 mg → 12 mg IV
3. IV CCB (verapamil, diltiazem) or β-blocker
4. Synchronized cardioversion if unstable

264.2.0.3 必背 — Vagal Maneuvers

• Modified Valsalva (REVERT trial) — 43% success (vs standard 17%); preferred
• Carotid massage (if no bruit, no severe carotid disease)

264.2.0.4 必背 — Adenosine

• 6 mg → 12 mg → (18 mg) IV rapid push + saline flush
• Brief AV node block
• Terminates re-entry SVT
• Avoid: WPW + AF, severe asthma, 2°/3° AV block

264.2.0.5 必背 — WPW + AF (Pre-Excited AF)

• AVOID AV nodal blockers (BB, CCB, digoxin, adenosine)
• Procainamide IV or cardioversion preferred
• Risk: very rapid ventricular response → VF

264.2.0.6 必背 — Antidromic AVRT (Wide QRS)

• Treat as VT until proven otherwise
• Procainamide IV or cardioversion

264.2.0.7 必背 — Catheter Ablation

• Curative for AVNRT, AVRT, typical AFL, AT (> 95% success)
• First-line for recurrent symptomatic
• Outpatient procedure
• Complications < 1% (AVNRT)

264.2.0.8 必背 — Multifocal Atrial Tachycardia (MAT)

• ≥ 3 P morphologies
• COPD + hypoxia + electrolytes + theophylline
• Treat underlying + magnesium + β-blocker (CCB if asthma)

264.2.0.9 必背 — AVNRT vs AVRT

• AVNRT: retrograde P hidden in QRS or just after; no accessory pathway
• AVRT: accessory pathway present (WPW baseline); P after QRS but later; orthodromic narrow, antidromic wide

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