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Extracardiac: Anticholinergic effects

conduction disturbances, prior MI, significant SHD, hypotension Other considerations: Reduces LV outflow tract obstruction and symptoms in HCM Flecainide Prolongs PR interval,

QRS duration, and

QT intervala PVC, VT (unmasking BrS

ECGb) 200–400 mg (1–2 mg/kg over

10 min) Cardiac: Pro-arrhythmia (MVT, occasional TdP), negative inotrope, sinus bradycardia, AV block, 1:1 AV conduction during flutter Extracardiac: Central nervous system effects (e.g. drowsiness, diplopia, headache)

Contraindications: Prior MI, significant SHD, BrS, severe sinus node dysfunction, severe AV or intraventricular conduction disturbances, inherited LQTS (other than LQTS3), severe kidney disease (CrCl ,35 mL/min/1.73 m2) Other considerations: Discontinue if QRS widening .25% or bundle branch block Isoproterenol Increases sinus node

frequency, shortens

QT interval (Electrical storm in BrS, idiopathic VF, and ERS, TdP,

beta-blocker overdose; acquired LQTS) No oral use (0.5–10 μg/min) Cardiac: Sinus tachycardia, vasodilation Extracardiac: Headache, sweating, tremor Contraindications: ACS, LQTS Other considerations: Short plasma half time (2 min)

Lidocaine No significant effects (VT/VF associated with

ACS) No oral use (50–200 mg bolus,

then 2–4 mg/min) Cardiac: Sinoatrial arrest Extracardiac: Central nervous system effects (e.g. drowsiness, dizziness)

Precautions: Reduced dose with reduced liver blood flow (e.g. shock, β-blockade, severe heart failure) Other considerations: More effective with high potassium level. Few haemodynamic side effects Mexiletine No significant effects PVC, VT

(LQT3) 600–1200 mg Loading dose: 400 mg initially followed by 600 mg in the first 24 h Cardiac: Sinus bradycardia in sinus node dysfunction, hypotension Extracardiac: Central nervous system effects (e.g. tremor, dysarthria, dizziness), gastrointestinal complaints Contraindications: Sinus node dysfunction, severe AV conduction disturbances, severe heart failure

Procainamide Prolongs PR interval,

QRS duration, and

QT intervala VT (100 mg bolus, can be repeated after 5 min if no effect, max 500–

750 mg [max 50 mg/min]. Then, 2–6 mg/min) Cardiac: Sinus bradycardia, hypotension, TdP Extracardiac: Rash, myalgia, vasculitis, systemic lupus, agranulocytosis

Contraindications: Severe sinus node dysfunction, severe AV conduction disturbances, severe intraventricular conduction disturbances, severe LV dysfunction hypotension, BrS Propafenone Prolongs PR interval,

QRS duration, and

QT intervala PVC, VT 450–900 mg Cardiac: Sinus bradycardia, AV block, negative inotrope, pro-arrhythmia (MVT, occasional TdP) Extracardiac: Gastrointestinal disturbances, headache, dry mouth Contraindications: Prior MI, significant SHD, BrS, severe sinus node dysfunction, severe AV or intraventricular conduction disturbances, LQTS, significant renal or liver disease Other considerations: Discontinue if QRS widening .25% or bundle branch block Downloaded from academic.oup.com/eurheartj/article/43/40/3997/6675633 by guest on 07 October 2026