Restoration of sinus rhythm: direct current cardioversion

Abstract

First introduced in 1962, electrical cardioversion represents an effective and safe therapy to restore sinus rhythm in patients with atrial fibrillation (AF). Consistent with the original description by Lown, cardioversion is obtained through a ‘brief high-energy capacitor-stored electric shock … discharged across the intact chest of the lightly anesthetized patient’, electronically programmed to fall outside of the ‘vulnerable period’ of ventricular repolarization. Procedures performed according to the original description differed very little from those performed today, although a most remarkable advance was represented by the upgrading from the initial monophasic to the actual biphasic shock waveform. With this technique, atrial and ventricular defibrillation thresholds and the probability of post-shock re-initiation of fibrillating activity could be reduced. The anteroapical dual electrode configuration is the most commonly used and self-adhesive paddles obviate the operator-dependent variability of electrode location, pressure, and surface contact on the chest. Acute cardioversion is indicated in subjects with new-onset AF, high-rate recurrent AF, or recurrent AF in the setting of severely impaired left ventricular function with haemodynamic instability. In all other cases, elective cardioversion is offered under adequate anticoagulation using an early or a delayed approach. Pre-treatment with antiarrhythmic drugs increases the likelihood of restoration of sinus rhythm and helps prevent recurrent AF. Arrhythmia duration, cardiac size, P-wave duration, presence of rheumatic heart disease, and previous cardioversion are predictors of AF recurrence. Post cardioversion, antiarrhythmic drugs are mandatory. Patients receiving long-term treatment with antiarrhythmic drugs have a larger probability of maintaining sinus rhythm during follow-up than patients receiving short-term treatment.