Arrhythmias: acute decisions

Adult professional education, not an order set. Use current local protocols, labeling and clinician judgment. No drug doses or shock energies are specified here.

Pulse → perfusion → width → regularity

No pulse

Start CPR and the cardiac-arrest pathway. Defibrillate VF/pulseless VT; not asystole/PEA. ^[1]

Tachyarrhythmia causing instability

Shock, hypotension, confusion, ischemic discomfort or acute HF attributable to the rhythm: synchronized cardioversion for organized tachycardia. Sedate if feasible without delay. Sustained polymorphic VT needs immediate unsynchronized shock. ^[1,2]

Stable, regular, narrow

For suspected re-entrant SVT, use vagal maneuvers/modified Valsalva, then adenosine when appropriate. Nodal block can expose atrial activity without terminating flutter. Treat the cause of sinus tachycardia. ^[1,2]

Stable, regular, monomorphic wide

Manage uncertain WCT as VT; consult and keep a defibrillator available during a drug attempt. Adenosine is limited to the stable, regular, monomorphic branch. Do not give verapamil/diltiazem for undifferentiated WCT. ^[1,2]

Irregular, wide, very fast / varying QRS

Consider pre-excited AF. Avoid AV-nodal blockers, including adenosine, beta-blockers, diltiazem/verapamil, digoxin and IV amiodarone. In a suitable stable patient: procainamide or ibutilide; instability: electrical cardioversion. Not every irregular WCT is pre-excited AF. ^[3]

Bradycardia with poor perfusion

Treat reversible causes and support perfusion. Atropine may help; refractory compromise requires pacing and/or an epinephrine/dopamine bridge per protocol. High-grade block: prepare pacing early; confirm mechanical as well as electrical capture. ^[1]

Before choosing an AF drug

Is AF causing the instability or accompanying sepsis, hypovolemia or another illness? Check EF, congestion, BP, pre-excitation, onset reliability and stroke-prevention context. Avoid IV diltiazem/verapamil in moderate/severe LV systolic dysfunction. Drug conversion also needs pericardioversion thromboembolic planning. ^[1,3]

Say the branch out loud: “This rhythm is / is not causing poor perfusion. I recommend ___ because ___. If ___ changes, our rescue is ___.”

Procainamide

Selected tolerated WCT or pre-excited AF, not a substitute for electricity in instability. During loading, stop for hypotension, arrhythmia termination, QRS increase >50%, or the protocol's maximum. Avoid with prolonged QT or HF; assess renal handling and NAPA. ^[2,3,4]

Recurrent torsades / long QT

Magnesium may be used even when the serum value is normal; remove triggers and correct electrolytes. Sustained polymorphic VT: immediate unsynchronized shock. Pause-dependent acquired torsades may need expert-directed pacing/rate support. Do not add QT-prolonging antiarrhythmics. Normal-QT polymorphic VT has a different treatment branch. ^[1]

Flecainide / propafenone

Screen for prior MI, significant structural disease, conduction defects and interactions. A pill-in-the-pocket plan needs prior monitored validation plus AV-nodal protection to reduce 1:1 flutter risk—not a guarantee of safety. CAST tested post-MI ectopy suppression; current guidance defines candidacy. ^[3,4]

Dofetilide / sotalol

Check QT, renal function, K/Mg, interacting drugs and the labeled initiation/re-initiation setting. Slower rates/pauses may amplify repolarization effects. TMP-SMX is contraindicated with dofetilide; separating doses does not solve it. The dofetilide label requires monitored initiation/re-initiation for at least 3 days. ^[4,5]

Amiodarone / digoxin handoff

Amiodarone effects/interactions persist after stopping. Review warfarin/INR and digoxin exposure with named follow-up ownership. Interpret digoxin concentrations with dose/sample timing, ECG, symptoms, electrolytes and renal function; an early post-load value alone does not diagnose toxicity. ^[6,7]

Hand off the decision, not just the drug name

Indication and endpoint · total exposure/last dose · ECG and perfusion response · stop criteria · organ/electrolyte trajectory · interaction changes · recurrence/rescue plan · who reviews what, and when.