Related Experiment Video
Updated: May 22, 2026

Laser-Induced Action Potential-Like Measurements of Cardiomyocytes on Microelectrode Arrays for Increased Predictivity of Safety Pharmacology
Published on: September 13, 2022
Propafenone Toxicity Presenting With Wide QRS and Transient Ventricular Dyskinesia
Larissa Araújo de Lucena1, Flávia da Costa Fernandes Mesquita1, Micheli Rigon Madeira2
1Hospital Universitário Onofre Lopes, Universidade Federal do Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil.
Background:
Propafenone, a class Ic antiarrhythmic with a narrow therapeutic window, may cause conduction disturbances.
Case Summary:
A 68-year-old man on propafenone presented with dyspnea and dizziness. Electrocardiogram showed QRS widening (160 milliseconds). Angiography excluded occlusion but showed transient ventricular dysfunction. Sodium bicarbonate normalized QRS complex and reversed dysfunction.
Conclusions:
New wide-QRS rhythm in patients on class Ic agents suggests sodium channel blocker toxicity. QRS narrowing after bicarbonate is diagnostically important. Early treatment ensures reversibility and prevents arrhythmias.
Take-Home Messages:
Toxicity in new wide-QRS rhythm on class Ic drugs should be assumed. QRS narrowing after bicarbonate is key. Early treatment prevents fatal complications.
Related Concept Videos
ECG Interpretation of Arrhythmias II: Atrial, Junctional and Ventricular Arrhythmias
Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers
Dysrhythmias IV: Characteristics of Bradyarrhythmias
Dysrhythmias III: Characteristics of Dysrhythmias
Dysrhythmias VI: Management of Dysrhythmias
Antiarrhythmic Drugs: Class IV Agents as Calcium Channel Blockers
Verapamil, a calcium channel blocker, inhibits calcium movement across myocardial cell membranes and vascular smooth muscle. This results in the dilation of coronary and...

