Diagnosis and Management of Hyperparathyroidism

Abstract

tient's normally conducted rhythm. The QRS change between native and wide morphologies can be explained based on the variable AV conduction in atrial fibrillation. When the AV conduction in atrial fibrillation is slower, resulting in longer RR interval, the QRS was narrower, as compared with rapid conduction leading to shorter RR interval and wider QRS because of flecainide-associated toxic effects. More importantly, the width of the wider QRS beats with shorter RR intervals progressively improved in this patient and transitioned to baseline-conducted QRS morphology over a period of a day with therapy. This suggests the arrhythmia was atrial fibrillation with conduction rather than dual tachycardia with atrial fibrillation and irregular ventricular tachycardia with similar QRS axis and progressively changing QRS widths.