Determinants of first-shock success for atrial implantable cardioverter defibrillators.
BACKGROUND
The aim of this study was to identify determinants of first-shock success for defibrillation of spontaneous atrial fibrillation (AF) in ambulatory patients with an atrial implantable cardioverter defibrillator (ICD). The determinants of first-shock success in ambulatory patients with atrial ICDs are unknown.


RESULTS
We used the generalized estimating equation method to analyze determinants of first-shock success in 50 consecutive atrial ICD recipients in whom DFT+ (weakest shock that defibrillates on two consecutive trials) was determined at implant and spontaneous AF was shocked with shock strength > or = 2 x DFT+. DFT+ was 6.2 +/- 3.1 J. Of 470 first shocks, 407 were successful (generalized estimating equation 85%, confidence interval 79% to 90%). Determinants of first-shock success were use of coronary sinus electrode (univariate P = 0.02; multivariate P < 0.001, relative risk 5.0), absence of a Class III antiarrhythmic drug (univariate P = 0.06; multivariate P < 0.001, relative risk 3.2), absence of early recurrence of atrial fibrillation (ERAF; univariate P = 0.06; multivariate P = 0.02, relative risk 2.9), and longer duration of AF prior to shock > or = 3 hours (univariate: P = 0.02; multivariate P = NS). Sinus rhythm >1 minute persisted after 93% of first shocks in patients without documented ERAF but after only 58% of shocks in patients with documented ERAF (P < 0.001).


CONCLUSIONS
Reducing ERAF is critical to achieving a clinically acceptable rate of persistent sinus rhythm after first shocks. For first shocks > or = 2 x DFT +, success is not increased by programming stronger shocks. Early cardioversion does not increase first-shock success.
Swerdlow
Charles D
CD
Cedars-Sinai Medical Center, Los Angeles, California, USA. swerdlow@ucla.edu
Schwartzman
David
D
Hoyt
Robert
R
Bailin
Steven J
SJ
Koehler
Jodi L
JL
Warman
Eduardo N
EN
D000553:Ambulatory Care / Q000379:methods; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use; D001281:Atrial Fibrillation / Q000628:therapy*; D001282:Atrial Flutter / Q000628:therapy*; D003131:Combined Modality Therapy / Q000379:methods; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D012008:Recurrence; D015203:Reproducibility of Results; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D016896:Treatment Outcome
D000889:Anti-Arrhythmia Agents