Rapid Review·HY Approach
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Cardiovascular
T1Must knowApproach to Tachyarrhythmias
Focus on
Two questions sort every fast rhythm: is the QRS narrow or wide, and is it regular or irregular? Then one more: is the patient stable? Unstable → synchronized cardioversion, whatever the rhythm. Stable narrow regular → vagal maneuvers and adenosine; irregular → AF/flutter/MAT pathways; wide → VT until proven otherwise.
Key takeaways
Palpitations
Resting electrocardiogram (ECG)
often normal between episodes.Continuous monitoring
to catch a transient arrhythmia.Outpatient monitoring
ambulatory monitoring (Holter, insertable monitor) suits a young patient (under 40) without structural heart disease.Admit
for monitoring and expedited evaluation when the patient is older, has structural disease (prior infarct), or has an abnormal ECG.Rate and instability
hemodynamic instability from a tachyarrhythmia usually needs a rate over 150.Classifying a Tachycardia
Stability
an unstable patient (any rhythm) gets synchronized cardioversion, no drugs first.QRS width
narrow (under 120 ms) is supraventricular; wide (120 ms or more) is ventricular or pre-excited.Rhythm
regular or irregular; manage by the box below.| Regular | Irregular | |
|---|---|---|
| Narrow | Sinus tachycardia (normal P before each QRS); AVNRT or orthodromic AVRT (no visible P or retrograde P); atrial flutter with fixed block (saw-tooth) | Atrial fibrillation (no P waves); multifocal atrial tachycardia (3 or more P shapes); flutter with variable block |
| Wide | Monomorphic ventricular tachycardia; antidromic AVRT; supraventricular tachycardia (SVT) with aberrancy (treat as VT until proven otherwise) | Polymorphic VT and torsades; atrial fibrillation with pre-excitation (WPW) |
Treating the Stable Patient
Stable narrow regular
vagal maneuvers, then adenosine; beta blockers or calcium-channel blockers as alternatives (AV Nodal Reentrant Tachycardia).Stable narrow irregular
rate control with a beta blocker or non-dihydropyridine calcium-channel blocker; treat the cause in multifocal atrial tachycardia (Atrial Fibrillation, Multifocal Atrial Tachycardia).Stable wide
by the rhythm.- Monomorphic VT: amiodarone (lidocaine, procainamide, sotalol); in a patient with a prior infarction, do not assume SVT with aberrancy.
- Torsades: magnesium.
- Pre-excited atrial fibrillation or antidromic atrioventricular re-entrant tachycardia (AVRT): procainamide; never an atrioventricular (AV) nodal blocker (Wolff-Parkinson-White Syndrome).
Atrial Arrhythmias
| Rhythm | Associations | ECG | Management |
|---|---|---|---|
| Sinus tachycardia | Pain, infection, exercise, hypovolemia, fear, hypoxia, anemia, pulmonary embolus | Regular, P before every QRS | Treat the cause |
| Atrial fibrillation | Hypertension, coronary disease, rheumatic disease, catecholamines, hyperthyroidism, atrial enlargement | Irregularly irregular, no P waves, erratic baseline, narrow QRS | Rate control plus anticoagulation; rhythm control or ablation |
| Atrial flutter | Right atrial re-entry at about 300 | Regular saw-tooth F waves, ventricular rate 150, 100 or 75 | As for fibrillation; ablation is first-line rhythm control |
| Multifocal atrial tachycardia | Severe lung disease (COPD), catecholamine excess | Irregular, 3 or more P morphologies, variable PR and R-R, 100 to 200 | Treat the lung disease |
| AV nodal re-entrant tachycardia (AVNRT) | Fast and slow pathways in the AV node | Regular narrow at 150 to 220, P buried or retrograde | Vagal maneuvers or adenosine |
| AVRT | AV node plus an accessory pathway | Regular at 150 to 250; orthodromic narrow with P after QRS, antidromic wide with short PR | Vagal maneuvers or adenosine (orthodromic) |
| Wolff-Parkinson-White (WPW) | Accessory pathway, familial, may bring atrial fibrillation | Short PR, delta wave, wide QRS in sinus rhythm | Procainamide; avoid AV nodal blockers |
A stable patient has an irregular wide-complex tachycardia at 240 with varying QRS shapes and a known delta wave in sinus rhythm. What is the rhythm, the drug, and the drug class to avoid?
Pre-excited atrial fibrillation (WPW): give procainamide (synchronized cardioversion if unstable). Never AV nodal blockers (adenosine, beta blockers, calcium-channel blockers, digoxin).
How it's tested
Regular narrow tachycardia at 180 that started abruptly in a healthy 25-year-old, BP 118/76: vagal maneuvers, then adenosine — AVNRT.
Same rhythm with BP 70/40 and confusion: synchronized cardioversion, no drugs first.
Irregular wide-complex tachycardia at 220 with varying QRS in a young man with a known delta wave: pre-excited AF — procainamide or cardioversion; adenosine or diltiazem could cause VF.
Regular wide-complex tachycardia in a man with a prior MI, stable: VT — amiodarone or procainamide; do not assume SVT with aberrancy.
Palpitations in a 68-year-old with a prior MI and a normal ECG: admit for monitoring — structural heart disease makes VT the concern.
Go deeper
Guidelines: 2025 AHA Adult Advanced Life Support Guidance · 2015 ACC/AHA/HRS Supraventricular Tachycardia Guideline
Related Step 2 pages: ECG Basics, AV Nodal Reentrant Tachycardia, Atrial Fibrillation, Atrial Flutter, Wolff-Parkinson-White Syndrome, Ventricular Tachycardia, Cardiac Arrest & ACLS
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