CARDIOVERSION OF ATRIAL-FIBRILLATION WITH LOW-ENERGY INTERNAL ELECTRIC-SHOCK

The efficacy and safety of low internal cardioversion for the reductio n of atrial fibrillation was assessed prospectively in 104 consecutive patients. Sixty-two patients had chronic atrial fibrillation (Group I ), 16 patients had paroxysmal atrial fibrillation (Group II) and 26 pa tients had induced atrial fibrillation (Group III), The average durati on of the current episode of atrial fibrillation was 9 +/- 19 months i n Group I, 4 +/- 2 days in Group II and 18 +/- 7 minutes in Group III. Two intracardiac defibrillation catheters were used, one (the cathode ) in the right atrium and the other in the coronary sinus or left bran ch of the pulmonary artery (anode). These catheters were connected to an external defibrillator delivering biphasic 3/3 ms shocks with a vol tage which could be programmed from 10 to 400 volts. The shocks were s ynchronised on the R wave. Sinus rhythm was restored in 44 of the 62 p atients in Group I (70 %), 12 of the 16 patients in Group II (75 %) an d 20 of the 26 patients in Group III (77 %). The average voltages and energies restoring sinus rhythm were 300 +/- 68 volts and 3.5 +/- 1.5 joules respectively in Group I, 245 +/- 72 volts and 2.0 +/- 2.9 joule s in Group II, and 270 +/- 67 volts and 2.6 +/- 1.2 joules in Group II I. These results show that the energy required to restore sinus rhythm is significantly greater in patients with chronic atrial fibrillation than in patients with paroxysmal or induced atrial fibrillation. Ther e were no ventricular proarrhythmic effects in the 686 shocks synchron ised on the R wave. This study shows that internal cardioversion of at rial fibrillation is feasible with low energies under simple sedation. These results support the concept of an implantable atrial defibrilla tor.