Drug & Class

Mechanism of Action + Uses

Side Effects + Contraindications

Procainamide (Class IA)

Moderate Na⁺ block + K⁺ block → ↑ APD & ↑ QT. 

Uses: Stable monomorphic VT, pre-excited AF (WPW + AF), SVT with aberrancy

QT prolongation → torsades, hypotension (IV), drug-induced lupus, agranulocytosis. 

Avoid in prolonged QT, severe LV dysfunction

Quinidine (Class IA)

Na⁺ + K⁺ block → slows conduction, ↑ QT. 

Uses: Rare in ICU; AF cardioversion (historical)

Torsades, cinchonism (tinnitus, headache), thrombocytopenia. Avoid in QT prolongation

Disopyramide (Class IA)

Na⁺ block + anticholinergic effect. 

Uses: Hypertrophic obstructive cardiomyopathy (HOCM)

Strong negative inotrope → HF worsening, urinary retention, glaucoma, torsades

Lidocaine (Class IB)

Weak Na⁺ block; acts on ischemic ventricular tissue; ↓ APD. 

Uses: Ischemic VT, VF (post-MI), refractory VF

CNS toxicity (seizures, confusion), hypotension. Avoid in severe AV block without pacemaker

Mexiletine (Class IB)

Oral lidocaine analogue. 

Uses: Chronic ventricular arrhythmias

GI upset, tremor, CNS toxicity

Flecainide (Class IC)

Strong Na⁺ block → marked conduction slowing. 

Uses: Paroxysmal AF (no structural heart disease)

Proarrhythmia, QRS widening, ↑ mortality post-MI (CAST trial). ❌ Contraindicated in structural heart disease

Propafenone (Class IC)

Na⁺ block + weak β-blockade. 

Uses: Pill-in-pocket AF (selected patients)

Metallic taste, bradycardia, proarrhythmia. Avoid in LV dysfunction

Drug & Class

Mechanism + Uses

Side Effects + Contraindications

Metoprolol (Class II)

Uses: AF with RVR, post-MI arrhythmia, electrical storm

Bradycardia, hypotension, bronchospasm. Avoid in severe asthma, decompensated HF

Esmolol (Class II)

Uses: ICU rate control, peri-intubation tachycardia, electrical storm

Hypotension, bradycardia. Avoid in AV block

Propranolol (Class II)

Uses: Thyroid storm arrhythmias, long QT

Bronchospasm, hypoglycemia masking

Drug & Class

Mechanism + Uses

Side Effects + Contraindications

Amiodarone (Class III, multi-channel)

Blocks Na, K, Ca + β-block

Uses: Stable VT, VF/pVT (ACLS), AF in structural heart disease, electrical storm

Pulmonary fibrosis, thyroid dysfunction (hypo/hyper), hepatotoxicity, corneal deposits, photosensitivity, bradycardia

Sotalol (Class III + β block)

Uses: AF, VT prevention

High torsades risk, renal dose adjustment required

Dofetilide (Pure Class III)

K⁺ channel block → ↑ QT. 

Uses: AF maintenance

Torsades, requires inpatient initiation

Ibutilide (Class III)

↑ slow inward Na current → ↑ APD. 

Uses: Acute AF/flutter cardioversion

High torsades risk → give Mg prophylactically

Drug & Class

Mechanism + Uses

Side Effects + Contraindications

Diltiazem (Class IV)

L-type Ca block → ↓ AV conduction. 

Uses: AF with RVR (stable)

Hypotension, bradycardia. Avoid in HFrEF, WPW + AF

Verapamil (Class IV)

Uses: SVT, AF rate control

Severe hypotension, heart block. Avoid in LV dysfunction

Drug

Mechanism + Uses

Side Effects + Contraindications

Adenosine

Transient AV nodal block. 

Uses: PSVT, diagnostic for narrow complex tachycardia

Flushing, chest pain, transient asystole. ❌ Avoid in asthma, irregular wide complex tachycardia

Magnesium sulfate

Stabilizes myocardium; suppresses early afterdepolarizations. 

Uses: Torsades de pointes, long QT

Flushing, hypotension in rapid infusion

Digoxin

↑ Vagal tone → ↓ AV conduction. 

Uses: AF in HFrEF, hypotensive AF

Toxicity: arrhythmias, visual changes, hyperkalemia. Avoid in WPW + AF

Situation

Absolutely Avoid

WPW + AF

Beta blocker, Diltiazem, Verapamil, Digoxin, Adenosine

Structural heart disease

Class IC drugs

Long QT

Class IA, Class III

Decompensated HFrEF

Verapamil, Diltiazem

Scenario

Drug of Choice

Stable monomorphic VT (structural heart disease)

Amiodarone

Stable monomorphic VT (no severe LV dysfunction)

Procainamide (often superior efficacy)

Ischemic VT (post-MI)

Lidocaine

Recurrent VT

Amiodarone infusion ± Beta blocker

Scar-related VT

Amiodarone

Scenario

Drug of Choice

Stable polymorphic VT (normal QT)

Amiodarone

Scenario

Drug of Choice

Torsades (any Mg level)

Magnesium sulfate IV (2 g)

Bradycardia-induced torsades

Isoproterenol or temporary pacing

Drug-induced QT prolongation

Stop offending drug + Mg

Scenario

Drug of Choice

Electrical storm (structural heart disease)

Amiodarone + Beta blocker (Esmolol/Metoprolol)

Refractory

Add Lidocaine

Ischemic trigger

Urgent revascularization

Sympathetic surge

Deep sedation ± Stellate ganglion block

Scenario

Drug of Choice

Stable AVNRT

Adenosine

If adenosine contraindicated

Diltiazem or Verapamil

Recurrent

Beta blocker

Scenario

Drug of Choice

Stable

Adenosine

Recurrent

Beta blocker

Scenario

Drug of Choice

Stable

Procainamide

Avoid

AV nodal blockers

Scenario

Drug of Choice

AF with RVR (stable, no HFrEF)

Diltiazem or Beta blocker

AF with RVR + HFrEF

Amiodarone or Digoxin

AF < 48 hrs (rhythm control)

Amiodarone

AF > 48 hrs

Rate control + anticoagulation

AF + WPW (pre-excited AF)

Procainamide

Scenario

Drug of Choice

Stable rate control

Diltiazem / Beta blocker

Rhythm conversion

Ibutilide or Amiodarone

Scenario

Drug of Choice

MAT (COPD patient)

Treat underlying + Magnesium

Rate control

Verapamil