Wide QRS Tachycardia in a Patient with Atrial Fibrillation: A Case Report and Approach to Diagnosis

Wide QRS tachycardia in patients with atrial fibrillation or atrial flutter treated with antiarrhythmic drugs can occur for a variety of reasons and needs careful evaluation for appropriate management of the patient. We report a case of wide QRS complex tachycardia in a patient with atrial fibrillation treated with Flecainide who received multiple external cardioversion attempts for a presumed diagnosis of ventricular tachycardia. Intravenous Diltiazem and an oral beta blocker led to the resolution of wide QRS complex tachycardia. Wide QRS tachycardia due to pro-arrhythmic effect or rate dependency phenomenon of antiarrhythmic agents should be included in the differentials. In this brief report, we discuss the differential diagnosis and outline a practical approach for acute and long-term management of these patients.