Flecainide Toxicity: A Case Report and Systematic Review of its Electrocardiographic Patterns and Management

Abstract

In the setting of flecainide toxicity, supraventricular tachycardia can manifest as a bizarre right or left bundle branch block, sometimes with a northwest axis, and can easily be mistaken for ventricular tachycardia leading to inappropriate therapy. We conducted a comprehensive literature review for cases of flecainide toxicity. We found 21 articles of flecainide toxicity in adult patients in which 22 ECG tracings were published. In patients with flecainide toxicity and QRS duration ≤ 200 ms, the ECGs were more likely to show RBBB, visible P waves (p = 0.03), and shorter QT (p = 0.02) and QTc intervals (p = 0.004). With QRS duration > 200 ms, the ECGs were more likely to show LBBB, loss of P waves, a northwest axis (p = 0.01), and longer QT and QTc intervals. Deaths were reported only in patients with QRS duration >200 ms, and the outcome of death or requirement for mechanical circulatory support was more prevalent in patients with a QRS duration > 200 ms [2/13 (15.4 %) vs. 6/10 (60 %), p = 0.04]. In patients with access to the medication, flecainide toxicity should be suspected with: (1) broad QRS, (2) RBBB morphology with QRS ≤ 200 ms; RBBB or LBBB morphology with QRS ≥ 200 ms (3) HR out of proportion to the degree of hemodynamic instability. The duration of the QRS interval is prognostic, with mortality and the requirement for mechanical circulatory support being more common in patients with a QRS > 200 ms.

Flecainide toxicity: a presentation to the emergency department with literature review

“…Those who have a QRS<200 ms are more likely to have p waves, compared with those who have a QRS>200 ms. The QT and QTc intervals are also shorter in those who have a QRS duration <200 ms 5…”

“…ECGs in cases presenting with flecainide overdose can be broadly split into two categories based on the QRS duration, depending on whether it is <200 ms or >200 ms. It is interesting to see that the length of QRS duration can also determine the type of bundle branch morphology 5…”

“…In patients who have a QRS>200 ms, the ECGs are more likely to show a left bundle branch block morphology. The need for mechanical ventilatory support is more prevalent with patients with a QRS duration >200 ms and there is also an associated increase in chance of mortality 5…”

Maternal monitoring and safety considerations during antiarrhythmic treatment for fetal supraventricular tachycardia

“…43,44 Maternal flecainide toxicity is managed with supportive care and aggressive intravenous bicarbonate administration, with or without intravenous fat emulsion. 45 In case of persistent hemodynamic compromise, extracorporeal membrane oxygenation may be required. 46 The landmark "Cardiac Arrhythmia Suppression Trial" demonstrated that flecainide was associated with increased mortality and nonfatal cardiac arrest in patients with recent myocardial infarction.…”

Wolff‐Parkinson‐White, Brugada phenocopy, and flecainide toxicity: All in one patient

“…Flecainide at supratherapeutic level in our patient is thought to have caused the conduction abnormalities manifesting as pauses, broad QRS, and PMVT. It is essential to have high index of suspicion for flecainide toxicity when encountering these arrhythmias in patients taking the drug …”