Internal right atrial cardioversion of chronic atrial fibrillation: Effects of low-energy biphasic shocks

Atrial fibrillation (AF) is associated with the loss of organized atrial contractions, a risk factor for thromboembolic events and hemodynamic deterioration. Therefore, the restoration of sinus rhythm, when feasible, is 1 of the major therapeutic options in patients with AF. For this purpose, antiarrhythmic drugs or external direct current (DC) shocks are attempted. Transthoracic electrical cardioversion has been shown to be effective in <80% of cases,(1,2) leaving > 20% off patients in AF. Internal cardioversion, which was introduced in the 1970s, has initially been disappointing.(3-5) However, in 1987, Levy et al(6) introduced intracavitary high-energy shocks (200 to 300 J) with a high success rate, a result that was subsequently confirmed in patients who could not be converted by external DC shocks,(7) even when associated with pharmacologic methods.(8) Moreover, internal shocks were reported to have some side effects due to the high-energy level delivered.(1,9) Efforts have recently been. made to lower this level. Different procedures have been proposed. The procedure most frequently reported has been the;right atrial-left atrial (via the coronary sinus or left pulmonary artery) DC shock. The success rate remains high with an energy level of generally < 5 J.(10-13) The main limitation for this intracavitary technique is the need for coronary sinus lead placement. This prompted us to study the efficacy of internal cardioversion with a "moderate" energy level, but with a simpler procedure.