Author + information
- William Escande, MD∗ (, )
- Eloi Marijon, MD, PhD,
- Pascal Defaye, MD, PhD,
- Olivier Piot, MD,
- Christophe Leclercq, MD, PhD,
- Nicolas Sadoul, MD, PhD,
- Jean-Claude Deharo, MD, PhD,
- Jean-Philippe Empana, PhD,
- Serge Boveda, MD and
- Didier Klug, MD, PhD
- ↵∗The Department of Cardiology, Institut Coeur-Poumons, CHRU de Lille, Bd du Pr Jules Leclercq, 59037 Lille Cedex, France
Electrical storms (ESs) are defined as clustered episodes (≥3) of recurrent ventricular tachycardia/ventricular fibrillation (VT/VF) that require appropriate therapies (antitachycardia pacing or shock) within a short time (24 h). We sought to evaluate the incidence, characteristics, and risk of death of patients who developed ESs or isolated VT/VF during follow-up in a large cohort of heart failure patients with implantable cardioverter-defibrillators (ICDs) implanted in the setting of primary prevention.
The DAI-PP (Défibrillateur Automatique Implantable-Prévention Primaire) registry enrolled 5,539 patients (age 18 years or older) with ischemic or dilated cardiomyopathy implanted with an ICD for primary prevention in 12 French centers between 2002 and 2012. Patients were separated into 2 risk profiles depending on the occurrence of ESs or isolated VT/VF during follow-up. Vital status and causes of death were ascertained by review of the patients’ medical files from the hospital or by communication with primary care physicians, and then corroborated with the French vital status database of the National Institute of Economic Statistics and the French Center on Medical Causes of Death. To evaluate the impact of ES occurrence on mortality, we used a Cox proportional hazard analysis, considering an ES to be a time-updated covariate. Analyses were performed with events censored at 4 years of follow-up.
Overall, information on the occurrence of an ES was available for 5,297 (95.6%) patients. The mean age of the population was 62.4 ± 11.1 years; 4,507 (85.9%) were men, 3,180 (60.5%) presented with coronary artery disease, and 4,312 (83.8%) had a left ventricular ejection fraction (LVEF) of <30%. During a mean follow-up of 3.1 ± 2.8 years, 156 (2.9%) patients developed at least 1 ES (giving an incidence rate of 9.2/1,000 person-years; 95% confidence interval [CI]: 7.7 to 10.6/1,000 person-years), 1,026 (19.4%) patients had an isolated VT/VF, and 4,115 (77.7%) patients had no arrhythmic episodes.
We observed no significant differences between the groups for other clinical conditions at baseline (age, type of cardiopathy, median LVEF, distribution of QRS width, New York Heart Association functional class, type of device implanted, or baseline medications). There were more men in the ES group (92.3% vs. 87.8% in the isolated VT/VF group and 84.1% in the no episodes group; p < 0.0005). There were more patients with renal failure (glomerular filtration rate [GFR] ≤60 ml/min) in the ES group (50.5% vs. 37.4% and 39.4%, respectively; p = 0.05).
In multivariate survival analysis, renal failure (defined as a GFR <60 ml/min) (hazard ratio [HR]: 1.8; 95% CI: 1.2 to 2.8; p = 0.007), LVEF <30% (HR: 1.7; 95% CI: 1.1 to 2.7; p = 0.03), and male sex (HR: 2.3; 95% CI: 1 to 5.2; p = 0.05) were associated with the occurrence of ESs.
All-cause mortality was substantially higher following ESs (140.44 per 1,000 person-years vs. 40.16 per 1,000 person-years) (Table 1), including a higher incidence of sudden cardiac death that was unresponsive to ICD therapy (43.89 per 1,000 person-years vs. 2.44 per 1,000 person-years, respectively; p < 0.0001). An increased risk of all-cause mortality was also observed following VT/VF (87.08 per 1,000 person-years vs. 40.16 per 1,000 person-years), including a higher incidence of sudden cardiac death that was unresponsive to ICD therapy (8.57 per 1,000 person-years vs. 2.44 per 1,000 person-years; p < 0.0001). Table 1 also shows that after consideration of confounders at ICD implantation, the occurrence of an ES was associated with an almost 4-fold increased risk of all-cause mortality (HR: 3.77; 95% CI: 2.48 to 5.73). Of note, the occurrence of VT/VF was related to a nearly 2-fold increased risk of all-cause mortality (HR: 1.77; 95% CI: 1.30 to 2.24).
In this large cohort of patients who underwent ICD implantation for primary prevention, ESs were rare events, with a particularly low annual incidence of approximately 1%, which was 4 to 6 times lower than that reported in secondary prevention (1). The incidence of isolated VT/VF was similar to the rates reported in randomized controlled trials in primary prevention, such as SCD-Heft (Sudden Cardiac Death-Heart Failure Trial) (2).
Whether the higher risk of mortality observed in the ES group is related to the underlying atrial and ventricular substrate or to electrical therapies itself remains unclear. The repetition of electrical therapies over time could have direct adverse effects on myocardial function through myocardial damage, inflammation, and electrical remodeling (3). Conversely, recent data from the ALTITUDE registry (4) has suggested that an adverse prognosis is more likely related to ventricular arrhythmias and atrial fibrillation in relation to the underlying myocardial substrate than that from the shock delivery itself. Optimal ICD programming, which focuses on the reduction of therapies, could be a safe and effective strategy in preventing subsequent morbidity and/or mortality from ICD shocks (5), but the effect on outcomes remains to be determined in the setting of ESs.
We acknowledge that information regarding the type of appropriate therapies (antitachycardia pacing or shock) and the use of catheter ablation of VT could have been useful. Furthermore, events were not centrally adjudicated. These were significant limitations because these data could have possibly affected interpretation of the clinical outcomes.
In conclusion, our findings suggest that ESs are rare events in primary prevention ICD recipients (approximately 1%), are more likely to occur among men, in patients with renal failure and particularly in those with a low ejection fraction. ESs are independently associated with poor outcomes.
Please note: The registry was funded by private (Association de Rythmologie Toulousaine – Clinique Pasteur) and public sources, including the French Institute of Health and Medical Research (Institut National de la Santé et de la Recherche Médicale; INSERM) and the French Society of Cardiology (Société Française de Cardiologie; SFC). Editorial support for the final version of the paper was provided by Sophie Rushton-Smith, PhD (MedLink Healthcare Communications Ltd.), and was funded by the authors. Dr. Piot has been a consultant for Medtronic; and has received research grants from Medtronic, St. Jude Medical, and Sorin. Dr. Klug has been a consultant for Medtronic, St. Jude Medical, Biotronik, and Sorin. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. (Clinical Trial Registration: Primary Prevention ICD French Registry; NCT01992458).
- 2016 American College of Cardiology Foundation
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