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Flecainide toxicity with high pacemaker capture thresholds and associated takotsubo syndrome
  1. Dario Manley-Casco1,
  2. Stephanie Crass2,
  3. Rana Alqusairi3 and
  4. Steven Girard4
  1. 1Internal Medicine, St Joseph Mercy Ann Arbor Hospital, Ann Arbor, Michigan, USA
  2. 2Internal Medicine, St Joseph Mercy Health System, Ann Arbor, Michigan, USA
  3. 3Internal Medicine, St Joseph Mercy Health System, Ypsilanti, Michigan, USA
  4. 4Cardiology, Michigan Heart Ann Arbor, Ypsilanti, Michigan, USA
  1. Correspondence to Dr Dario Manley-Casco; manleydario{at}


We describe a case of a woman in her 80s with persistent atrial fibrillation (AF) despite being on flecainide who was admitted for AF with rapid ventricular response. Attempts with direct-current cardioversions were unsuccessful despite increased doses of the antiarrhythmic therapy. At atrioventricular (AV) nodal ablation, very high right ventricular capture thresholds resulted in abortion of the procedure as back-up ventricular pacing could not be assured with adequate margin for safety. Shortly following the electrophysiology (EP) study, the patient developed cardiogenic shock with new apical left ventricular regional wall motion abnormality suggestive of apical ballooning and a toxic-appearing wide QRS complex electrocardiogram (EKG). The patient was successfully treated with sodium bicarbonate infusion for presumed flecainide toxicity. The regional wall motion abnormality and EKG changes resolved along with normalisation of capture thresholds after 2 days of treatment. The patient underwent an uncomplicated successful AV nodal ablation several weeks later.

  • arrhythmias
  • heart failure
  • pacing and electrophysiology
  • cardiovascular system
  • contraindications and precautions

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  • Contributors DM-C worked on the conception of the case and prepared the manuscript draft. SC worked on data interpretation and prepared the manuscript draft. DM-C and SC have contributed equally to the case and both are considered to be the first authors. RA contributed to data acquisition and critically reviewed the draft. SG revised the case critically for important intellectual content. All authors approved the final version of the case for publishing.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.