VT, Torsades, and VF
Key criteria and management for wide-complex ventricular rhythms and how to tell VT from SVT with aberrancy.
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Questions Covered in This Set
13 cards to master
Definition of ventricular tachycardia (VT)
Three or more consecutive ventricular beats at a rate >100 bpm; wide (≥0.12 s), bizarre QRS complexes.
Non-sustained vs. sustained VT
NSVT self-terminates in <30 seconds; sustained VT lasts ≥30 seconds or requires intervention.
Typical VT strip criteria
Rate 100–250 bpm (classically 150–200), regular rhythm, wide monomorphic QRS, absent or dissociated P waves, T waves often opposite the QRS.
Monomorphic vs. polymorphic VT
Monomorphic: every QRS looks identical, usually scar-related (old MI). Polymorphic: QRS shape changes beat to beat, think acute ischemia or channelopathy.
Management of VT based on pulse
Pulseless VT → unsynchronized defibrillation + CPR. Pulse but unstable → synchronized cardioversion. Pulse and stable → antiarrhythmics (amiodarone, procainamide, lidocaine) and expert help.
Which drug class must never be given for wide-complex tachycardia?
AV-nodal blockers such as verapamil — if the rhythm is VT, they can kill the patient.
What is Torsades de Pointes?
A polymorphic VT in the setting of a long QT interval; QRS amplitude waxes and wanes and the axis twists around the baseline, often triggered by an R-on-T PVC.
Causes of Torsades
Hypokalemia, hypomagnesemia, hypocalcemia, QT-prolonging drugs (macrolides, fluoroquinolones, haloperidol, methadone, ondansetron, antiarrhythmics), and congenital long QT syndromes.
Specific treatment for Torsades
IV magnesium sulfate (even if serum magnesium is normal), correct potassium, stop the offending drug, defibrillate if pulseless.
Ventricular fibrillation (VF) appearance and treatment
Chaotic irregular undulations with no P waves, QRS, or T waves and no cardiac output; always pulseless — treat with immediate defibrillation and high-quality CPR.
Coarse vs. fine VF
Coarse (large amplitude) suggests recent onset; fine (low amplitude) suggests longer downtime and can be mistaken for asystole.
VT vs. SVT with aberrancy — clinical rule
Assume VT until proven otherwise: ~80% of wide-complex tachycardias are VT, and >90% in patients with prior MI or structural heart disease.
Feature that is nearly diagnostic of VT
AV dissociation — independent P waves marching through at their own slower rate (fusion and capture beats also favor VT).
