Author + information
- Received September 17, 2019
- Revision received November 12, 2019
- Accepted November 14, 2019
- Published online March 16, 2020.
- Ihab Elsokkari, MDa,∗ (, )
- Ratika Parkash, MD, MSa,
- Anthony Tang, MDb,
- George Wells, PhDc,
- Steve Doucette, MScd,
- Elizabeth Yetisir, MSce,
- Martin Gardner, MDa,
- Jeffrey S. Healey, MD, MScf,
- Bernard Thibault, MDg,
- Laurence Sterns, MDh,
- David Birnie, MDi,
- Pablo Nery, MDi,
- Soori Sivakumaran, MDj,
- Vidal Essebag, MD, PhDk,
- Paul Dorian, MDl and
- John Sapp, MDa
- aDivision of Cardiology, Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, Canada
- bDivision of Cardiology, Western University, Ontario, Canada
- cCardiovascular Methods Centre, University of Ottawa Heart Institute, Cardiovascular Methods Center, Ottawa, Ontario, Canada
- dResearch Methods Unit, Dalhousie University, Halifax, Nova Scotia, Canada
- eCardiovascular Methods Centre, University of Ottawa Cardiovascular Methods Centre, Ottawa, Ontario, Canada
- fDepartment of Medicine, Division of Cardiology, Population Health Research Institute, Hamilton, Ontario, Canada
- gDepartment of Medicine, Montreal Heart Institute, Montreal, Quebec, Canada
- hDepartment of Medicine, Division of Cardiology, Royal Jubilee Hospital, Victoria, British Columbia, Canada
- iDepartment of Medicine, Division of Cardiology, University of Ottawa Heart Institute, Ottawa, Ontario, Canada
- jDepartment of Medicine, Division of Cardiology, University of Alberta, Edmonton, Alberta, Canada
- kDepartment of Medicine, Division of Cardiology, McGill University Health Centre and Hopital Sacre Coeur de Montreal, Montreal, Quebec, Canada
- lDepartment of Medicine, Division of Cardiology, University of Toronto, Toronto, Ontario, Canada
- ↵∗Address for correspondence:
Dr. Ihab Elsokkari, Queen Elizabeth II Health Sciences Centre, 1796 Summer Street, Room 2501, Halifax, B3H 3A7 Nova Scotia, Canada.
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.
Supported by the Cardiac Arrhythmia Network of Canada (CANet) as part of the Networks of Centres of Excellence (NCE). Dr. Parkash has received personal fees from Medtronic and Abbott. Dr. Tang has received a research grant from the Canadian Institute of Heath Research and Medtronic of Canada. Dr. Healey has received grants from Medtronic and Boston Scientific. Dr. Sapp has received grants from Biosense Webster and Abbott; and has received personal fees from Medtronic and Abbott. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the JACC: Clinical Electrophysiology author instructions page.
- Received September 17, 2019.
- Revision received November 12, 2019.
- Accepted November 14, 2019.
- 2020 American College of Cardiology Foundation
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