A systematic review and meta-analysis of the association between implantable cardioverter-defibrillator shocks and long-term mortality.
BACKGROUND
It is unknown whether implantable cardioverter-defibrillator (ICD) discharges actively contribute to a worse prognosis independent of the underlying arrhythmia. There is considerable variability in the reported risk of mortality after appropriate and inappropriate ICD shocks. The aim of our systematic review was to provide a reliable effect size of the association between ICD shock and mortality for both types of therapies.


METHODS
On the basis of a systematic literature search, 10 studies were considered eligible for inclusion in the analysis, and data on the hazard ratio (HR) of mortality after ICD shock were extracted from each study.


RESULTS
On pooled analysis, a substantial difference was detected in the risk for subsequent mortality between appropriate and inappropriate shocks. Among patients receiving an appropriate ICD shock, the HR for cardiac death was 2.95 (95% confidence interval [CI], 2.12-4.11; P < 0.001) compared with an HR of 1.71 (95% CI, 1.45-2.02) for those receiving an inappropriate shock. Clinical variables like ejection fraction, New York Heart Association class, and length of follow-up did not affect the HRs in our meta-regression models.


CONCLUSIONS
Our analysis showed a significant association between appropriate and inappropriate ICD shocks and mortality, with a stronger association for appropriate shocks. Previous trials of ICD therapy reduction programming have shown a significant reduction of inappropriate shocks. The management of appropriate shocks is more challenging and may be optimized by the assessment and treatment of the underlying ventricular arrhythmias. The role of therapies aimed at modifying the arrhythmic substrate and the potential impact on ICD shocks and mortality requires further investigation.
McGill University Health Center, Montréal, Québec, Canada; Cardiology Department, Luigi Sacco Hospital, Milan, Italy. Electronic address: riccardoproietti6@gmail.com.
Riccardo
R
Proietti
McGill University Health Center, Montréal, Québec, Canada.
Christopher
C
Labos
McGill University Health Center, Montréal, Québec, Canada.
Mark
M
Davis
McGill University Health Center, Montréal, Québec, Canada.
George
G
Thanassoulis
Cardiology Department, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Pasquale
P
Santangeli
Second Chair of Cardiology, Monaldi Hospital, Naples, Italy.
Vincenzo
V
Russo
Texas Cardiac Arrhythmias Institute, St. Davids Medical Center, Austin, Texas, USA; Albert Einstein College of Medicine at Montefiore Hospital, New York, New York, USA.
Luigi
L
Di Biase
McGill University Health Center, Montréal, Québec, Canada; Division of Cardiology, Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, Québec, Canada.
Jean-Francois
JF
Roux
McGill University Health Center, Montréal, Québec, Canada; Southlake Regional Health Centre, Newmarket, Ontario, Canada.
Atul
A
Verma
Texas Cardiac Arrhythmias Institute, St. Davids Medical Center, Austin, Texas, USA; Case Western Reserve University, Cleveland, Ohio, USA; EP Services, California Pacific Medical Center, San Francisco, California, USA; Interventional Electrophysiology, Scripps Clinic, San Diego, California, USA.
Andrea
A
Natale
McGill University Health Center, Montréal, Québec, Canada; Hôpital Sacré-Cœur de Montréal, Montréal, Québec, Canada.
Vidal
V
Essebag
D001145:Arrhythmias, Cardiac / Q000401:mortality* / Q000628:therapy*; D017147:Defibrillators, Implantable / Q000009:adverse effects*; D006333:Heart Failure / Q000401:mortality* / Q000628:therapy*; D006801:Humans; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D016019:Survival Analysis