What is the clinical evidence from this study?

Study design: Observational. Population: Ischemic or Dilated Cardiomyopathy with ICD for primary prevention (n=561). Intervention: Appropriate ICD shocks vs. No appropriate ICD shocks. Primary outcome: All-cause mortality (HR 1.48, 95% CI 0.96-2.28, p=0.072).

May 10, 2013Open Access

Impact of Shocks on Mortality in Patients with Ischemic or Dilated Cardiomyopathy and Defibrillators Implanted for Primary Prevention

Key Result

Appropriate ICD shocks were associated with reduced survival in patients with ischemic cardiomyopathy (HR 1.61) but not in patients with dilated cardiomyopathy (HR 1.03) implanted for primary prevention.

Study Design

Type

Observational (n=561)

Multicenter

PICO

Population

Ischemic or Dilated Cardiomyopathy with ICD for primary prevention (n=561)

Intervention / Comparator

Appropriate ICD shocks vs No appropriate ICD shocks

Primary Outcome

All-cause mortality — HR 1.48 (0.96-2.28), p=0.072

Main Result

Effect estimate: HR 1.48 (95% CI 0.96-2.28)

p-value: p=0.072

Limitations

Observational design cannot prove causality between shocks and death
Not powered to determine significant differences between compared groups if mortality rate differences were below 5 percentage points
Recommendations for ICD programming changed over time, potentially influencing the incidence of appropriately delivered shocks
Viability studies were not performed in all patients, so some ICM patients may have had cardiomyopathy out of proportion to coronary disease

Abstract

BACKGROUND: Emerging interest is seen in the paradox of defibrillator shocks for ventricular tachyarrhythmia and increased mortality risk. Particularly in patients with dilated cardiomyopathy (DCM), the prognostic importance of shocks is unclear. The purpose of this study was to compare the outcome after shocks in patients with ischemic cardiomyopathy (ICM) or DCM and defibrillators (ICD) implanted for primary prevention. METHODS AND RESULTS: Data of 561 patients were analyzed (mean age 68.6±10.6 years, mean left ventricular ejection fraction 28.6±7.3%). During a median follow-up of 49.3 months, occurrence of device therapies and all-cause mortality were recorded. 74 out of 561 patients (13.2%) experienced ≥1 appropriate and 51 out of 561 patients (9.1%) ≥1 inappropriate shock. All-cause mortality was 24.2% (136 out of 561 subjects). Appropriate shock was associated with a trend to higher mortality in the overall patient population (HR 1.48, 95% CI 0.96-2.28, log rank p = 0.072). The effect was significant in ICM patients (HR 1.61, 95% CI 1.00-2.59, log rank p = 0.049) but not in DCM patients (HR 1.03, 95% CI 0.36-2.96, log rank p = 0.96). Appropriate shocks occurring before the median follow-up revealed a much stronger impact on mortality (HR for the overall patient population 2.12, 95% CI 1.24-3.63, p = 0.005). The effect was driven by ICM patients (HR 2.48, 95% CI 1.41-4.37, p = 0.001), as appropriate shocks again did not influence survival of DCM patients (HR 0.63, 95% CI 0.083-4.75, p = 0.65). Appropriate shocks occurring after the median follow-up and inappropriate shocks occurring at any time revealed no impact on survival in any of the groups (p = ns). CONCLUSION: Appropriate shocks are associated with reduced survival in patients with ICM but not in patients with DCM and ICDs implanted for primary prevention. Furthermore, the negative effect of appropriate shocks on survival in ICM patients is only evident within the first 4 years after device implantation.

Bookmark

View Full Paper