What is the clinical evidence from this study?

Study design: Cohort. Population: Implantable cardioverter-defibrillator (ICD) patients (n=1544). Intervention: Inappropriate ICD shocks vs. No inappropriate shocks. Primary outcome: All-cause mortality (HR 1.6, p=0.01).

What question did this study set out to answer?

This study aims to evaluate the incidence, predictors, and outcomes of inappropriate shocks in patients with implantable cardioverter-defibrillators.

April 25, 2026

Inappropriate Implantable Cardioverter-Defibrillator Shocks

Key Result

Experiencing a single inappropriate ICD shock was associated with an increased risk of all-cause mortality (HR 1.6, p=0.01), with the risk increasing up to HR 3.7 after 5 shocks.

Key Points

This study aims to evaluate the incidence, predictors, and outcomes of inappropriate shocks in patients with implantable cardioverter-defibrillators.
Included all recipients of ICDs with electrogram storage from 1996 to 2006.
Clinically assessed patients at implantation and noted inappropriate ICD shocks during follow-up.
Follow-up duration averaged 41 months.
13% of ICD patients experienced at least one inappropriate shock during follow-up.
Each subsequent inappropriate shock raised mortality risk: HR of 1.6 for one shock, up to HR of 3.7 after five shocks.
Independent predictors included history of atrial fibrillation (HR: 2.0) and age younger than 70 years (HR: 1.8).

Study Design

Type

Cohort (n=1,544)

Structured PICO

Does the occurrence of inappropriate ICD shocks increase the risk of all-cause mortality in patients with implantable cardioverter-defibrillators?

Population

1,544 recipients of implantable cardioverter-defibrillator (ICD) devices equipped with intracardiac electrogram storage, mean age 61 ± 13 years, 79% male.

Intervention

Occurrence of inappropriate ICD shocks

Comparator

No inappropriate ICD shocks

Outcome

Incidence of inappropriate ICD shocks and all-cause mortalityhard clinical

Inappropriate ICD shocks are common in real-world practice and are independently associated with a dose-dependent increase in all-cause mortality.

Main Result

Effect estimate: HR 1.6

p-value: p=0.01

Abstract

OBJECTIVES: The purpose of this study was to assess the incidence, predictors, and outcome of inappropriate shocks in implantable cardioverter-defibrillator (ICD) patients. BACKGROUND: Despite the benefits of ICD therapy, inappropriate defibrillator shocks continue to be a significant drawback. The prognostic importance of inappropriate shocks outside the setting of a clinical trial remains unclear. METHODS: From 1996 to 2006, all recipients of defibrillator devices equipped with intracardiac electrogram storage were included in the current analysis and clinically assessed at implantation. During follow-up, the occurrence of inappropriate ICD shocks and all-cause mortality was noted. RESULTS: A total of 1,544 ICD patients (79% male, age 61 ± 13 years) were included in the analysis. During the follow-up period of 41 ± 18 months, 13% experienced ≥1 inappropriate shocks. The cumulative incidence steadily increased to 18% at 5-year follow-up. Independent predictors of the occurrence of inappropriate shocks included a history of atrial fibrillation (hazard ratio HR: 2.0, p < 0.01) and age younger than 70 years (HR: 1.8, p = 0.01). Experiencing a single inappropriate shock resulted in an increased risk of all-cause mortality (HR: 1.6, p = 0.01). Mortality risk increased with every subsequent shock, up to an HR of 3.7 after 5 inappropriate shocks. CONCLUSIONS: In a large cohort of ICD patients, inappropriate shocks were common. The most important finding is the association between inappropriate shocks and mortality, independent of interim appropriate shocks.