Failure of Intracardiac Pacing After Fatal Propafenone Overdose: A Case Report

Propafenone is a sodium-channel blocker, class IC antiarrhythmic drug, frequently used to manage supraventricular dysrhythmias, especially atrial fibrillation. We report a self mono-intoxication with propafenone.

A 68-year-old woman presented with a decreased level of consciousness, hypotension, and electrocardiogram showing QRS widening with atrial asystole and extreme bradycardia < 20 beats/min. After initial stabilization with transcutaneous pacing, laboratory findings detected normal electrolyte ranges and metabolic acidosis, and her medical history revealed availability of propafenone due to paroxysmal atrial fibrillation and depressive syndrome, which led to the suspicion of intoxication. Despite intravenous sodium bicarbonate, calcium, norepinephrine, and aggressive fluid replacement (10% glucose with insulin), hemodynamic stability was not achieved. Temporary intracardiac pacing was implanted. However, even with multiple electrode positions, effective capture could not be achieved. At that time, transcutaneous pacing was also ineffective. Consequently, the patient died in refractory asystole due to complete myocardial nonexcitability. The concentration of 5270 ng/mL of propafenone was found in the blood at autopsy, using gas spectrometry-mass chromatography. It is the third highest reported propafenone lethal concentration and the first case in which the myocardial nonexcitability refractory to intracardiac pacing was seen despite normal electrode position in the right ventricle, with failure to achieve the patient's hemodynamic stability. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Emergency physicians should be aware of possible propafenone ingestion causing toxicity, which is probably more frequent than previously described, especially because propafenone is widely available due to its use in managing atrial fibrillation, the most common arrhythmia nowadays.