[Intra-atrial defibrillation--limits and possibilities].

Unlabelled: External cardioversion has been a remarkably effective and safe method for termination of atrial fibrillation. Originally introduced by Lown and coworkers in 1962, it has been an accepted mode of acute therapy. The disadvantages of this approach are the need for general anaesthesia and the demand for high energies up to 360 J. Intraatrial defibrillation of atrial fibrillation using low energy shocks has been intermittently investigated as an alternative to the external method for over two decades. The following aspects have to be considered during the use of intraatrial defibrillation: the efficacy of this method, the safety, i.e. the potential risk of inducing a proarrhythmic, the patient acceptance during recurrent shock discharges, the phenomenon of the atrial stunning, the risk of a thromboembolism, and the necessity of anticoagulation. Our own experience of 25 patients and the data in the literature indicate that internal atrial defibrillation is a safe and effective method for termination of atrial fibrillation, and is particularly useful in patients who have been refractory to external cardioversion. The mean atrial defibrillation threshold for termination of chronic atrial fibrillation was 9.1 +/- 7.4 J in our patient population, corresponding with a leading edge voltage of 376 +/- 175 V and an impedance of 53 +/- 8 omega. At an energy level of 300 V, 40% of the patients could be effectively converted into sinus rhythm. Apart from the induction of three ventricular depolarizations no other proarrhythmic events could be observed during the delivery of approximately 200 shock discharges, in particular no sustained ventricular tachyarrhythmias. The mean pain score at 60 V was 3.0 +/- 1.1 corresponding with a mild discomfort, and at 140 V 4.6 +/- 0.7 corresponding with a moderate to severe discomfort. Serial multiplane transesophageal echocardiographic examinations demonstrated a reduction of the flow in the left atrial appendage following intraatrial defibrillation. These reduced flows in the left atrial appendage recovered within 7 days. On June 3, 1996 an atrial defibrillator was successfully implanted for the first time in Germany in a patient with symptomatic, drug refractory atrial fibrillation.

Conclusions: Intraatrial defibrillation is a safe and effective method for termination of atrial fibrillation. The electrotherapy with an implantable atrial defibrillator should be considered as an alternative approach in patients with symptomatic, long lasting, and drug refractory episodes of atrial fibrillation.