IMPLANTABLE ATRIAL DEFIBRILLATORS

Due to the limited efficacy of antiarrhythmic drugs for atrial fibrill ation, several nonpharmacologic therapeutic options have evolved, One of these is an implantable atrial defibrillator. Recent studies have s hown that internal atrial defibrillation is feasible with relatively l ow energies. To date, the optimal electrode configuration involves lar ge surface area catheters in the right atrium and coronary sinus. In h umans, atrial defibrillation can generally be achieved with < 2 J usin g this electrode configuration and a biphasic shock waveform, For shoc ks < 5 J, there is no significant pathological damage to the atria or coronary sinus, Further investigation is needed to guarantee that atri al defibrillation shocks do not provoke ventricular arrhythmias. Preli minary data suggest that atrial defibrillation shocks synchronized to R waves that are not closely coupled are safe, In addition, the shocks are well tolerated if the shock energy is < 1.5 J, With additional st udies to confirm the safety of implantable atrial defibrillators, furt her reduce shock energy, and improve patient tolerance, an implantable atrial defibrillator can become an acceptable therapy for patients wi th symptomatic, paroxysmal atrial fibrillation.