title: Low-energy intracardiac shocks during atrial fibrillation: effects on cardiac rhythm.
abstract: The effect on ventricular rate of intracardiac shocks for atrial fibrillation was studied in 13 patients receiving 95 shocks. Shocks were synchronized to the R wave and were delivered after R-R intervals > 500 msec, with increasing strength (20 to 400 V). In 10 patients, conversion to sinus rhythm was achieved in this way. Noneffective shocks increased the mean first postshock R-R interval (compared with 20 V as baseline), for shocks > or = 140 V. The R-R prolongation correlated with the shock level (r = 0.936, p < 0.01). Subsequent R-R intervals were comparable to baseline. A similar trend toward longer first postshock intervals was observed for effective shocks. However, the maximal first R-R interval after noneffective shocks had no relation to the voltage. The number of pauses > 1500 msec tended to increase with voltage (noneffective shocks). Pauses > 2500 msec were exceptional (4 of 85 noneffective shocks). No symptomatic bradycardia occurred. In subsequent intervals (cycles 2 through 10) no pauses > 2500 msec were noted. It is concluded that atrial defibrillation attempts between the right atrium and coronary sinus prolong R-R intervals, in relation to administered energy, but without the need for backup pacing.
authors.affiliation: Department of Cardiology, University Hospital Ghent, Belgium.
authors.forename: N
authors.initials: N
authors.lastname: Gjorgov
authors.forename: F
authors.initials: F
authors.lastname: Provenier
authors.forename: L
authors.initials: L
authors.lastname: Jordaens
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000628:therapy*; D001919:Bradycardia / Q000209:etiology; D004554:Electric Countershock / Q000009:adverse effects / Q000379:methods*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome