Q: Flecainide toxicity can be seen on EKG as (select one)

A) QRS prolongation
B) QTc interval prolongation
C) inversion of T wave
D) U wave
E) J point elevation


Answer:  QRS prolongation

Signs of flecainide toxicity are sometime not so apparent and early and best monitoring is looking at EKG (or Telemetry pattern). Flecainide toxicity should be suspected if there is a 50% increase in QRS duration or 30% prolongation in PR interval, especially at rapid heart rates. 



Reference: 

 1. Katristis D, Rowland E, O'Nunain S, Shakespeare C, Poloniecki J, Camm A (1995). "Effect of flecainide on atrial and ventricular refractoriness and conduction in patients with normal left ventricle Implications for possible antiarrhythmic and proarrhythmic mechanisms". Eu Heart J 16 (1): 1930–1935 

2.  Lloyd T, Zimmerman J, Griffin GD. Irreversible third-degree heart block and pacemaker implant in a case of flecainide toxicity. Am J Emerg Med. 2013;31:1418.e1-2. 

3. Courand PY, Sibellas F, Ranc S, Mullier A, Kirkorian G, Bonnefoy E. Arrhythmogenic effect of flecainide toxicity. Cardiol J. 2013;20:203-205. 

4. Levis JT. ECG diagnosis: flecainide toxicity. Perm J. 2012;16:53. 

5. Rognoni A, Bertolazzi M, Peron M, et al. Electrocardiographic changes in a rare case of flecainide poisoning: a case report. Cases J. 2009;3:9137.