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Fig. 4. Radiograph of a balloon flotation catheter with proximal and distal-shock electrode segments in the right atrium and left pulmonary artery used for internal cardioversion. The catheter is under clinical investigation at the present time.

Fig. 4. Radiograph of a balloon flotation catheter with proximal and distal-shock electrode segments in the right atrium and left pulmonary artery used for internal cardioversion. The catheter is under clinical investigation at the present time.

surgery. Besides their use for temporary atrial pacing in the postoperative setting, low-energy cardioversion through the epicardial atrial electrodes successfully terminated AF in 80-89% of patients (73,74). When no longer needed, the temporary electrodes could be removed through the skin by traction. Although potentially very useful for treatment of postoperative AF, these temporary pacing/defibrillation wires are still considered investigational in the United States.

Another alternative in patients refractory to standard external cardioversion is the use of two external defibrillators, either simultaneously or nearly simultaneously (75,76). For this technique, two sets of adhesive skin pads are placed on the patient. Simultaneous delivery offers the obvious advantage of increasing the energy applied. Nearly simultaneous sequential delivery may be successful if the first shock lowers the chest wall impedance, so that more of the energy of the second shock penetrates to the myocardium. If the two discharges are not timed appropriately, there is a risk of inducing ventricular fibrillation (VF).

Although some antiarrhythmic drugs have anecdotally been associated with increasing the efficacy of cardioversion, few data are available. Oral and colleagues studied the use of the iv class III agent ibutilide as an adjunct to cardioversion using a monophasic waveform (77). This randomized trial demonstrated that this drug significantly improved the efficacy of cardioversion, and significantly reduced the energy requirement for restoration of sinus rhythm. Three percent of patients who received ibutilide developed PVT requiring ventricular defibrillation.

As techniques to restore sinus rhythm have improved, it has become clear that in many patients, sinus rhythm can be transiently restored, with then an immediate or early recurrence of AF (ERAF). This may be caused by AF-induced atrial electrophysiologic remodeling (78). Preliminary evidence suggests that verapamil pretreatment may attenuate the risk of ERAF (79).

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