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Mortality Risk Increases With Clustered Ventricular Arrhythmias in Patients With Implantable
Ihab Elsokkari1, Ratika Parkash1, Anthony Tang2
1Division of Cardiology, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, Canada.
Insights
Even two ventricular arrhythmia (VA) events within three months indicate a worse prognosis. This risk escalates with increased arrhythmia burden and shorter cluster durations, highlighting the prognostic significance of VA clustering.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Statistics
Background:
- Electrical storm, defined as ≥3 ventricular arrhythmia (VA) episodes in 24 hours, is linked to adverse outcomes.
- The prognostic impact of arrhythmia clusters outside this definition remains less understood.
Purpose of the Study:
- To investigate the adverse prognosis associated with ventricular arrhythmia clusters beyond the traditional electrical storm definition.
- To analyze the impact of varying cluster lengths and event counts on patient outcomes.
Main Methods:
- Analysis of 14,515 implantable cardioverter-defibrillator-detected events from the Resynchronization in Ambulatory Heart Failure trial.
- Clustering defined as ≥2 VA events within 3 months; prognostic importance evaluated by varying cluster parameters.
- Comparison of mortality rates between patients with clustered, unclustered, or no arrhythmias.
Main Results:
- Patients with clustered VA (≥2 events/3 months) faced a significantly higher mortality risk (HR: 2.68) compared to those with no arrhythmia.
- Even the least dense cluster (2 VA events/3 months) showed increased mortality risk (HR: 2.85).
- Mortality risk increased with higher VA burden and shorter cluster length, with implantable cardioverter-defibrillator shocks associated with higher risk than antitachycardia pacing.
Conclusions:
- Clustered ventricular arrhythmias, even as few as 2 events within 3 months, are significantly associated with adverse prognosis.
- The prognostic risk increases with greater cluster density (more events in shorter periods).
- Findings suggest refining arrhythmia monitoring and management strategies for patients with clustered VA events.
Objectives:
This study sought to examine the adverse prognosis associated with ventricular arrhythmia clusters that falls outside the current electrical storm definition.
Background:
Electrical storm is most frequently defined as a cluster of ≥3 episodes of ventricular arrhythmia (VA) in a 24-h period. This definition has been associated with adverse cardiovascular outcomes and mortality, but the effect of lesser and greater clustering of arrhythmias has not been described.
Methods:
Among all patients in the Resynchronization in Ambulatory Heart Failure trial, 14,515 implantable cardioverter-defibrillator-detected events with data available were rigorously adjudicated in blinded fashion. Arrhythmia incidence was examined for clustering, defined as 2 or more VA events occurring within 3 months. The prognostic importance of clustering was analyzed by varying the cluster length and number of events used to define a cluster. Mortality rates of groups with clustered arrhythmias were compared to patients with no arrhythmia or with unclustered arrhythmia.
Results:
The trial included 1,764 patients, among whom 465 patients had two or more VA episodes within 3 months, whereas 406 had unclustered arrhythmias. Compared to patients with no arrhythmia, patients experiencing unclustered VA had increased risk of death (hazard ratio [HR]: 1.45; 95% confidence interval [CI]: 1.09 to 1.93; p = 0.011), whereas the risk was even higher in patients with clustered arrhythmia (HR: 2.68; 95% CI: 2.13 to 3.36; p < 0.0001). Mortality risk increased with higher VA burden (number of VAs in a cluster) and shorter cluster length. This was observed in all groups tested, including the cluster with the least VA burden in the longest cluster length tested (2 VA episodes occurring within 3 months) (mortality HR: 2.85; 95% CI: 1.95 to 4.17; p < 0.0001). Although clustered arrhythmias terminated with antitachycardia pacing were associated with increased mortality, clusters terminated with implantable cardioverter-defibrillator shocks were associated with still higher mortality risk.
Conclusions:
Significant adverse prognostic association of clustered VAs is observable with even 2 VA events within 3 months and increases with higher cluster density.
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