Flecainide Toxicity Resulting in Pacemaker Latency and Intermittent Failure to Capture

Area of Science:

• Cardiology
• Pharmacology

Background:

• Flecainide is a Class Ic antiarrhythmic drug for supraventricular and ventricular arrhythmias.
• Flecainide has a significant adverse effect profile, but its impact on pacemakers is not well-documented.

Observation:

• A 91-year-old female on flecainide presented with syncope and bradycardia.
• She had acute kidney injury with elevated creatinine and flecainide toxicity (3.09 mcg/mL).
• ECG showed atrial and ventricular pacing with wide QRS and significant ventricular capture latency.

Findings:

• Flecainide toxicity increased the patient's pacemaker ventricular capture threshold significantly.
• This toxicity manifested as ventricular capture latency and intermittent pacemaker failure to capture.

Implications:

• Flecainide toxicity can increase ventricular pacing thresholds in patients with pacemakers.
• Clinicians should consider flecainide toxicity in pacemaker patients presenting with capture issues, especially with renal impairment.