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Background: Dofetilide is a class III antiarrhythmic often used for the treatment of atrial fibrillation. Given its QTc prolonging properties, it is invariably initiated in an inpatient setting. While admissions for this drug are often unexciting, pharmacologic cardioversion in general and dofetilide in particular carry unique hazards. Objective: To review a case where several risk factors converged during a dofetilide load to produce a life threatening event. Case: A 75 year old male in persistent atrial fibrillation was admitted for dofetilide and started on 500 mcg PO Q12 (based on QTc and GFR). He did not experience any QTc prolongation after his first two doses, and converted to sinus rhythm on his second day of hospitalization. With this, he had an abrupt decrease in heart rate from 110 to 60 bpm. Within minutes, he suddenly developed flash pulmonary edema and required treatment for acute heart failure with IV diuresis. Fortunately, he improved with therapy in time to receive his third dose, after which QTc remained at 450. However, he had non sustained polymorphic ventricular ectopy overnight. His full AM dose was given before the monitor was reviewed (given his normal QTc), and within 2 hrs of this fourth dose, QTc prolonged markedly. He developed ventricular bigeminy with long-coupled PVCs. Subsequently, he developed sustained torsades requiring chest compressions and defibrillation. The patient recovered well, and dofetilide was discontinued. Conclusion: Acute heart failure after restoration of sinus rhythm is an uncommon but known complication of cardioversion, both electrical and pharmacologic. Furthermore, hemodynamic derangement is known to decrease arrhythmia threshold, which, along with his abrupt drop in heart rate and recent diuresis, likely contributed to the development of torsades. Furthermore, while his QTc appeared numerically acceptable before the fourth dose was given, later review revealed an abnormal T wave morphology with prolonged T peak to end time, which might have prompted a dose change if recognized. In short, monitoring dofetilide patients involves more than just GFR and QTc - other observable factors can portend poor outcome.

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