Narrow-complex tachycardias

Differentiate sinus tach, AFib, AFlutter, SVT — and pick the right move.

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◆Rapid pattern recognition

•Sinus tach: rate 100–150, P before every QRS, regular — treat the underlying cause
•AFib: irregularly irregular, NO discrete P waves, baseline fibrillation — rate control + anticoagulate
•Atrial flutter: 'sawtooth' flutter waves (best in II/III/aVF), regular if conduction is constant (often 2:1 at 150 bpm)
•AVNRT / AVRT (SVT): regular narrow tach 150–250, NO visible P waves (buried in QRS), abrupt onset/offset
•MAT: ≥3 different P-wave morphologies, irregular, rate >100 — associated with COPD; treat hypoxia

•Unstable (hypotension, AMS, chest pain, CHF) → synchronized cardioversion regardless of rhythm
•Stable SVT → vagal maneuvers → adenosine 6 mg IV (then 12 → 12)
•Stable AFib RVR → β-blocker or non-DHP CCB (diltiazem) for rate control
•Stable AFlutter → same rate control; consider cardioversion if recent onset
•MAT: treat COPD, give magnesium; AVOID β-blockers (bronchospasm)

•CHA₂DS₂-VASc ≥2 (men) or ≥3 (women) → anticoagulate (DOAC preferred over warfarin)
•Valvular AFib (mod–severe MS or mechanical valve) → WARFARIN only
•Cardioversion: if AFib >48 hr or unknown → 3 weeks anticoag before OR TEE to rule out clot; then 4 weeks after

Rhythm	EKG hallmark
Sinus tachycardia	P before every QRS, rate 100–150
AFib	Irregularly irregular, NO P waves
Atrial flutter	Sawtooth F waves; often 2:1 at exactly 150
SVT (AVNRT)	Regular 150–250, hidden P, abrupt on/off
MAT	≥3 P morphologies, irregular (COPD)

◆Regular narrow tach at exactly 150 → think atrial flutter with 2:1 block
◆Adenosine both treats AND diagnoses — unmasks flutter waves if not SVT
◆AFib + WPW (wide bizarre irregular tach) → procainamide; AVOID AV nodal blockers (adenosine, β-blocker, CCB, digoxin)
◆Holiday-heart AFib: ETOH-triggered, often self-terminates

Quick check

Test yourself before moving on. ~1 min.

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