Medications to Avoid in Bundle Branch Block

Introduction to High-Risk Medications

The European Society of Cardiology recommends avoiding Class IC antiarrhythmic drugs (flecainide, propafenone) in patients with bundle branch block and structural heart disease or ischemia, and exercising extreme caution with any medication that can worsen conduction abnormalities or precipitate complete heart block 1
The American College of Cardiology/American Heart Association (ACC/AHA) guidelines warn that flecainide/propafenone should not be used in patients with left bundle branch block, ischemic heart disease, or structural heart disease 2

Out-of-hospital drug termination should be avoided in patients with symptomatic sick sinus syndrome, AV conduction disturbances, or bundle branch block due to risk of severe bradycardia and conduction abnormalities 1
Class IC agents can cause sustained monomorphic ventricular tachycardia and increase defibrillation threshold, particularly problematic in bundle branch block patients 1

Verapamil is contraindicated in wide QRS-complex tachycardias of unknown etiology 2
Digoxin, beta-blockers, diltiazem, verapamil, and amiodarone are contraindicated in patients with pre-excited atrial fibrillation as they may increase the risk of ventricular fibrillation 2

Amiodarone is no longer recommended for acute management of narrow-QRS tachycardias 2
Amiodarone should not be used for acute treatment of pre-excited atrial fibrillation 2
Disopyramide is no longer recommended for chronic treatment of focal atrial tachycardia 2
Procainamide and quinidine are no longer recommended during pregnancy 2

The presence of ischemic heart disease, structural heart disease, or heart failure dramatically increases the risk of proarrhythmic effects from Class IC agents 1, 2
Any medication that further impairs AV conduction or His-Purkinje conduction should be used with extreme caution and close monitoring 1, 3
Patients with acute MI and new bundle branch block should not receive permanent pacing in the absence of second- or third-degree AV block, but medications that worsen conduction should still be avoided 3, 5, 6, 7
Athletes with bundle branch block and sinus bradycardia require careful evaluation before any rate-slowing or conduction-blocking medications 4
Do not use Class IC agents for "pill-in-the-pocket" approach in patients with bundle branch block without prior in-hospital testing 1