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Published on: February 28, 2012
Risk factors and outcomes associated with failed implantable cardioverter-defibrillator shocks
Amole Ojo1, Scott McNitt1, Mehmet K Aktaş1
1Clinical Cardiovascular Research Center, Department of Medicine, University of Rochester Medical Center, Rochester, New York.
Insights
Failed implantable cardioverter-defibrillator (ICD) shocks predict adverse outcomes. Younger age, male sex, heart failure hospitalization, and prior successful shocks are key predictors of ICD shock failure in primary prevention patients.
Area of Science:
- Cardiology
- Medical Devices
- Electrophysiology
Background:
- Implantable cardioverter-defibrillators (ICDs) are crucial for preventing sudden cardiac death by terminating ventricular tachycardia/fibrillation (VT/VF).
- Failure of ICD shocks to terminate VT/VF indicates a high-risk patient group, even if immediate death is averted.
- Understanding factors predicting shock failure is vital for optimizing patient management and device therapy.
Purpose of the Study:
- To identify predictors of failed appropriate ICD shocks in patients receiving primary prevention ICDs.
- To determine the outcomes associated with failed appropriate ICD shocks in this patient population.
- To aid in risk stratification for patients with reduced left ventricular ejection fraction.
Main Methods:
- Analysis of a large cohort (5512 patients) from the Multicenter Automatic Defibrillator Implantation Trials and the Ranolazine in High-Risk Patients With Implanted Cardioverter-Defibrillator trial.
- Utilized Cox proportional hazards multivariate regression modeling to identify risk factors for the first occurrence of a failed ICD shock.
- Examined baseline clinical characteristics and device-related events as potential predictors.
Main Results:
- The 3-year rate of appropriate ICD shocks for VT/VF was 14.6%, with a 3.1% rate of at least one failed shock.
- Younger age, male sex, and heart failure hospitalization post-implantation were significant baseline predictors of failed ICD shocks.
- A prior successful ICD shock was the strongest predictor of subsequent failed shocks (HR, 6.72).
Conclusions:
- Identified simple clinical risk factors that can effectively stratify patients at risk for failed ICD shocks.
- These findings can inform clinical decision-making and potentially improve outcomes for high-risk individuals.
- Further research may explore targeted interventions for patients identified as high-risk for ICD shock failure.
Background:
Implantable cardioverter-defibrillators (ICDs) deliver shocks to terminate ventricular tachycardia/ventricular fibrillation (VT/VF) to reduce the risk of sudden cardiac death. Failure of ICD shocks to terminate VT/VF, even if not resulting in death immediately, may signal patients at high risk of adverse outcomes.
Objective:
We sought to identify predictors and outcomes associated with failed appropriate ICD shocks in patients with reduced left ventricular ejection fraction with a primary prevention ICD.
Methods:
Our study cohort consisted of 5512 patients with an ICD or cardiac resynchronization therapy-defibrillator who were enrolled in the landmark Multicenter Automatic Defibrillator Implantation Trials and the Ranolazine in High-Risk Patients With Implanted Cardioverter-Defibrillator trial. Cox proportional hazards multivariate regression modeling was used to identify risk factors associated with the first occurrence of a failed ICD shock.
Results:
Through 3 years of follow-up, the Kaplan-Meier rate of appropriate ICD shocks for VT/VF was 14.6% and rate of at least 1 failed ICD shock for VT/VF was 3.1%. Baseline risk factors associated with failed ICD shocks included younger age (hazard ratio [HR], 1.21 per 10 years younger age; 95% confidence interval [CI], 1.03-1.42; P = .019), male sex (HR, 2.21; 95% CI, 1.26-3.86; P = .006), and the occurrence of heart failure hospitalization after device implantation (HR, 2.06; 95% CI, 1.35-3.16; P = .001). Notably, the delivery of a successful ICD shock after device implantation was the most powerful risk factor for subsequent failed ICD shocks (HR, 6.72; 95% CI, 4.39-10.30; P < .001).
Conclusion:
Our study identifies simple clinical risk factors that may be used to risk stratify patients at risk of having a failed ICD shock.
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