The correct answer is: D. Start intravenous ibutilide

The patient presents with medically refractory, irregular wide-complex tachycardia. The differential diagnosis includes pre-excited atrial fibrillation (i.e., atrial fibrillation in a patient with ventricular pre-excitation), ventricular tachycardia, and supraventricular tachycardia with aberrant conduction. One of the hallmarks of pre-excited AF is the very rapid ventricular rate owing to the short refractory period of the accessory pathway. The ventricular rate approaches 300 beats/minute on the presenting electrocardiogram. Other features that help distinguish pre-excited AF from the other possibilities are the irregularity and varying QRS morphology. Although one may occasionally encounter ventricular tachycardia with varying cycle lengths, the degree of irregularity demonstrated on the electrocardiogram is more consistent with AF. The changing QRS morphology results from varying degrees of fusion, that is, due to activation over both the accessory pathway and the atrioventricular (AV) node.

In patients with atrial fibrillation in the setting of ventricular pre-excitation, conduction of electrical impulses can occur preferentially via the accessory pathway due to its shorter refractory period as compared to the AV node. For the same reason, AV nodal blocking agents like adenosine, verapamil, beta-blockers or digoxin should be avoided in patients with atrial fibrillation with pre-excited AF, which since they may result in exacerbating tachycardia, and may contribute to the development of ventricular fibrillation and hemodynamic collapse.

Control of ventricular rate and termination of atrial fibrillation, if possible, are the main goals of therapy for atrial fibrillation with pre-excitation.¹ Parenteral drug therapy with anti-arrhythmics that can slow conduction both in AV nodal and accessory pathways should be tried for treatment of hemodynamically stable patients. Intravenous ibutilide prolongs the refractoriness of the both and has been found to be very useful for acute termination of atrial fibrillation.² IV Procainamide may be used if ibutilide is not available because of its effect on atrial myocardium. If AF persists, the ventricular rate usually slows due to effects of procainamide on refractoriness and conduction over the accessory pathway. Intravenous amiodarone can be tried if ibutilide or procainamide are unavailable, but such patients should be monitored on continuous telemetry. Electrical cardioversion should be performed for patients who are hemodynamically unstable.^1,3

Patients presenting with pre-excited AF should be referred for catheter ablation of the accessory pathway, not only to eliminate symptoms of palpitations but also to eliminate the risk of sudden death. The accessory pathway responsible for pre-excited AF or supraventricular tachycardia can be eliminated in about 95% of patients with a low risk of complications (1%).⁴

References

1. Fuster V, Ryden LE, Cannom DS, et al. ACC/AHA/ESC 2006 Guidelines for the Management of Patients with Atrial Fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 Guidelines for the Management of Patients With Atrial Fibrillation): developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. J Am Coll Cardiol 2006;48:854-906.
2. Glatter KA, Dorostkar PC, Yang Y, et al. Electrophysiological effects of ibutilide in patients with accessory pathways. Circulation 2001;104:1933-1939.
3. Link MS, Atkins DL, Passman RS, et al. Part 6: electrical therapies: automated external defibrillators, defibrillation, cardioversion, and pacing: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122(18 Suppl 3):S706-719.
4. Scheinman MM, Huang S. The 1998 NASPE prospective catheter ablation registry. Pacing Clin Electrophysiol 2000;23:1020-1028.
5. Dagres N, Clague JR, Lottkamp H, Hindricks G, Breithardt G, Borggrefe M. Impact of radiofrequency catheter ablation of accessory pathways on the frequency of atrial fibrillation during long-term follow-up; high recurrence rate of atrial fibrillation in patients older than 50 years of age. Eur Heart J 2001;22:423-427.