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Archives of cardiovascular diseases
Volume 106, n° 11
pages 562-569 (novembre 2013)
Doi : 10.1016/j.acvd.2013.07.002
Received : 17 April 2013 ;  accepted : 16 July 2013
Defibrillation testing in everyday medical practice during implantable cardioverter defibrillator implantation in France: Analysis from the LEADER registry
Le test de défibrillation lors de l’implantation d’un DAI dans la pratique médicale quotidienne en France : analyse à partir du registre LEADER
 

Nicolas Sadoul a, , Pascal Defaye b, Elisabeth Mouton c, Olivier Bizeau d, Jean-Marc Dupuis e, Hugues Blangy a, Nicolas Delarche f, Jean-Jacques Blanc g, Arnaud Lazarus h
on behalf of

the LEADER registry investigators

a CHU, 54511 Nancy, France 
b CHU, 38043 Grenoble, France 
c Boston Scientific, 78960 Voisins-le-Bretonneux, France 
d Centre hospitalier régional, 45067 Orléans, France 
e CHU, 49033 Angers, France 
f Centre hospitalier, 64046 Pau, France 
g CHU, 29607 Brest, France 
h Clinique Ambroise-Paré, 92200 Neuilly, France 

Corresponding author. Département de Cardiologie, CHU, rue du Morvan, 54511 Vandœuvre-les-Nancy cedex, France.
Summary
Background

Defibrillation testing (DT) is usually performed during implantable cardioverter defibrillator (ICD) implantation.

Aims

We conducted a multicentre prospective study to determine the DT procedures used in everyday practice, to compare the characteristics of patients with or without DT, and to compare severe adverse events in these two populations during implantation and follow-up.

Methods

The LEADER registry enrolled 904 patients included for primo-implantation of a single (n =261), dual (n =230) or triple (n =429) defibrillation system in 42 French centres.

Results

Baseline characteristics of patients (62.0±13.5 years; 88% men; primary indication 62%) who underwent ventricular fibrillation (VF) induction (VF induction group, n =810) and those who did not (untested group, n =94, representing 10.4% of the entire study population) revealed that the untested group were older (P <0.01), had a lower left ventricular ejection fraction, a wider QRS complex and a higher New York Heart Association class and were more often implanted for primary prevention (P <0.001 for all). The main reason given for not performing ICD testing was poor haemodynamic condition (59/94). At 1 year, the cumulative survival rate was 95% in tested patients and 85% in untested patients (P <0.001), mainly because of heart failure deaths. There was one sudden cardiac death in the VF induction group and none in the untested group (P =1.000).

Conclusions

In this study, more than 10% of ICD patients were implanted without VF induction. Untested patients appeared to be sicker than tested patients, with a more severe long-term outcome, but without any difference in mortality due to arrhythmic events.

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Résumé
Contexte

Les tests de défibrillation (DT) sont généralement effectués lors de l’implantation d’un défibrillateur automatique implantable (DAI).

Objectifs

Cette étude prospective multicentrique a été réalisée afin de : déterminer quelles sont les procédures utilisées pour réaliser les DT dans la « vraie vie » ; comparer les caractéristiques des patients avec ou sans DT ; et comparer les événements secondaires graves entre ces deux populations au cours de l’implantation et du suivi.

Méthodes

Dans le registre LEADER, 904 patients (62,0±13,5ans ; 88 % hommes, indication primaire=62 %) ont été inclus dans le cadre d’une primo-implantation d’un système de défibrillation simple (n =261), double (n =230) ou triple (n =429) chambre dans 42 centres français.

Résultats

Les caractéristiques de base des patients ayant subi une induction de FV (groupe avec induction de FV, n =810) et ceux non testés (groupe non testé, n =94, représentant 10,4 % de l’ensemble de la population de l’étude) a révélé que les patients non testés étaient significativement plus âgés (p <0,01) et avait une FEVG inférieure, un QRS plus large, une classe NYHA supérieure et ont été plus souvent implantés pour une indication primaire (p <0,001 pour tous). La principale raison rapportée pour ne pas effectuer les tests de défibrillation était un mauvais état hémodynamique (59/94). Après 1 an, le taux de survie cumulé était de 95 % chez les patients testés contre 85 % chez les patients non testés (p <0,001), principalement suite à des décès pour insuffisance cardiaque. Il n’y a eu qu’une seule mort subite dans le groupe avec induction de FV et aucune dans le groupe non testé (p =1,000).

Conclusions

Dans cette étude multicentrique,>10 % des patients sont implantés avec un DAI sans induction de VF. Les patients non-testés semblent être de condition plus précaire que les patients testés avec un résultat à long terme plus péjoratif, mais sans différence dans la mortalité due à des événements rythmiques.

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Keywords : Implantable cardioverter defibrillator, Ventricular tachyarrhythmia, Defibrillation testing, Safety margin

Mots clés : Défibrillateur automatique implantable, Tachyarythmie ventriculaire, Test de défibrillation, Marge de sécurité

Abbreviations : AF, DFT, DT, ICD, LVEF, NYHA, VVI


Background

During implantable cardioverter defibrillator (ICD) implantation procedures, it is common practice to induce ventricular fibrillation (VF) to assess the reliability of the device for VF detection and termination. Until the early 2000s, patients underwent several VF inductions, usually using a step-down protocol with decreasing energies, to determine the defibrillation threshold (DFT) [1, 2]. Today, DFT determination is rarely performed, but a ≥ 10J safety margin for efficient defibrillation is required [3, 4, 5]. DFT determination is, however, still considered as a critical part of a successful implantation procedure, even though Swerdlow et al. [6] reported, from a review of the literature, that in 25–50% of ICD recipients, testing could not be identified as either critical or contraindicated.

Although the risk associated with defibrillation testing (DT) is low [6, 7, 8], VF induction is not a risk-free procedure. Serious complications may occur such as transient ischaemic attack, cardiopulmonary arrest, cardiogenic shock and embolic events, especially in the case of atrial fibrillation (AF), and even death (<1%) [7, 9, 10]. These complications may be a consequence of VF induction per se and/or the difficulty in defibrillating the heart.

Physicians have recently focused on the usefulness of DT, for several reasons: the increasing number of ICDs implanted [10]; changes in ICD technology resulting in lower DFTs [11, 12]; availability of high energy devices; and the spread of cardiac resynchronization therapy with ICD backup in patients who may not tolerate VF induction exhibiting DT complications [13]. There is an increasing body of literature on the outcome of patients implanted without DT [9, 13, 14, 15]. Most of these studies are focused on the immediate outcome of DT with little or no data on short- or long-term follow-up. The main objectives of the LEADER registry were to determine DT procedures in everyday clinical practice, to compare the characteristics of patients with or without VF induction, and to compare severe adverse events between these two populations during the implantation procedure and at 1-year follow-up.

Methods
Study population

All patients received an ENDOTAK RELIANCE® (Guidant/Boston Scientific, Natick, MA, USA) active or passive ICD lead, with a single or dual coil, connected to a single dual ICD (Vitality® ICD) or a defibrillator with cardiac resynchronization therapy/triple chamber ICD (RENEWAL®; Guidant/Boston Scientific, Natick, MA, USA). The patients included in this trial were ≥ 18 years of age and underwent a first ICD implantation for primary or secondary prevention indications according to the French and European Society of Cardiology guidelines [16, 17].

This observational study was approved by the French Ministry of Scientific Research and the French Privacy Authority. Written informed consent to participate in the registry was obtained from each patient. The study complied with the principles of the 1975 Declaration of Helsinki.

Data collection and patient follow-up

Baseline and clinical data were collected at inclusion, as were data on procedural characteristics, device implantation-related adverse events and device programming at the time of hospital discharge. Patients were subsequently divided in two groups: patients who underwent VF induction at implantation or before hospital discharge (VF induction group); and patients who did not undergo VF induction (untested group).

The patients were followed up at 3–6 months and at 12 months after the implantation. DT procedures were left to the investigator's discretion, but reasons for not performing a VF induction at implantation were recorded prospectively. ICD programming parameters for tachycardia or bradycardia were also left at the investigator's discretion.

Statistical methods

Statistical analysis was performed using SAS V9.2 (SAS Institute, Cary, NC, USA). Descriptive statistics were used to analyse the data. The level for statistical significance was defined as P <0.05. For continuous variables, sample size, mean, standard deviation, minimum, median, first quartile, third quartile, maximum and number of missing data were reported. For discrete variables, numbers of missing data, frequency and percentage by modality were collected. For variables with the modality “unavailable” or “not done”, percentages were calculated by exclusion of missing values and non-informative categories (e.g. “unavailable” or “not done”). For comparison tests between subgroups, the following analyses were used: variance analysis for quantitative variables (or analysis of variance on ranks when normality assumptions were not met); and the chi-squared test (or Fisher's exact test when the expected number in at least one cell is ≤ 5) for dichotomous variables.

Numbers of events per patient were compared using rank ANOVA analysis. Time-to-event analyses were conducted using Kaplan–Meier rates to estimate the percentage of patients with no events at specified time intervals.

Results
Study population

Patient characteristics are given in Table 1. In total, 904 patients were enrolled in 42 centres, representing half of all French ICD implantation centres. Primary prevention implantation was performed in 560 patients (62%). Baseline characteristics of patients in the VF induction group (n =810) and the untested group (n =94) revealed that untested patients were older (P <0.01), had a lower left ventricular ejection fraction (LVEF), a wider QRS complex and a higher New York Heart Association (NYHA) class and were more often implanted for primary prevention (P <0.001 for all), (Table 1). The therapy regimen was identical in the two groups except for beta-blocker therapy, which was more common in the VF induction group (74.6% versus 63.8%; P =0.035). The rate of untested patients remained stable during the course of the study, representing 10.4% of the entire study population. The mean follow-up was 10.5±5.1 months (0–15 months).

Procedural testing and early complications (≤30 days)

In the 810 patients in the VF induction group, four could not be induced despite repeated inductions. Among the 806 remaining patients, 74.8% (603/806) underwent one, 21% underwent two (169/806) and 4.2% (34/806) underwent three or more VF inductions, mainly due to routine medical practice. In total, 92.2% (743/806) of the 806 successfully induced patients had a safety margin ≥ 10J. Such a safety margin could not be obtained in 60/63 patients despite polarity shock reversal (n =45) and/or right ventricle lead repositioning (n =18) and/or disconnection of the proximal coil (n =2), whereas a single coil lead was replaced by a dual coil lead in one patient and a high energy device was implanted in two patients (1.1 changes/patient). No modification was attempted in the remaining three patients (investigator's decision). Among the 94 patients in the untested group, the main reason given by the implanting physician for not performing DT was poor haemodynamic condition (59/94). Other reasons included primary ICD indication (n =11), AF (n =9), lack of available anaesthesiologist (n =3), pacemaker dependency (n =3), other cardiac reasons (n =2) and tamponade at implantation (n =1). The reason for not performing DT could not be obtained in six patients.

Early (≤ 30 days postimplantation) fatal and non-fatal serious complications occurred in 68 patients. Eight patients died within a month of implantation, seven in the VF induction group (0.9%) and one in the untested group (1.1%; P =0.59) (Table 2). In the VF induction group, there were four cardiac deaths (0.5%) (heart failure in two patients, 9 and 18 days after implant; one myocardial infarction at day 6; one electromechanical dissociation at day 12) and three non-cardiac deaths (0.4%). One patient in the untested group experienced cardiogenic shock the day after implantation and died at day 8.

Non-fatal serious adverse events (i.e. new or prolonged hospitalization or leading to a new intervention) occurred in 60 patients (Table 3). Sixty-two complications occurred in 52 VF-induction patients (6.8%) and nine complications in eight patients in the untested group (10.1%; P =0.26).

Complications during long-term follow-up (>30 days)

During long-term follow-up, 54 patients died, 40 in the VF induction group (4.9%) and 14 in the untested group (14.9%) (P <0.001). Detailed information is given in Table 2. There was a sixfold increase in heart failure deaths in the untested group (9.6%) compared with the VF induction group (1.6%; P <0.001). One sudden cardiac death occurred in the VF induction group and none in the untested group (P =1.000).

Non-fatal serious adverse events occurred in 180 patients (Table 3): 218 complications were reported in 158 VF induction group patients (20.7%) and 30 complications in 22 untested group patients (27.8%; P =0.15). There were no differences in the rates of device-related complications, arrhythmic complications (appropriate or inappropriate therapies) and device-related infections between the two groups. Non-cardiac events were more frequent in the untested group (P <0.01) (Table 3).

Patient survival

At 1 year, the cumulative survival rate was 95% in the VF induction group and 85% in the untested group (P <0.001; Figure 1); the cumulative rate of survival free of hospitalization was 73% in the VF induction group and 58% in the untested group (P <0.001; Figure 2). In the VF induction group, the subset of patients with a safety margin<10J exhibited a higher total mortality than patients with an adequate safety margin (14.3% versus 5.1%; P =0.008), due to a higher rate of non-cardiac death with no difference in arrhythmic death. The rates of unknown causes of death (1.6% versus 0.7%; P =0.39) did not differ between groups.



Figure 1


Figure 1. 

Kaplan–Meier analysis of survival free from death in the VF induction group versus the untested group. VF: ventricular fibrillation.

Zoom



Figure 2


Figure 2. 

Kaplan–Meier analysis of survival free from hospitalization in the VF induction group versus the untested group. VF: ventricular fibrillation.

Zoom

Discussion

This prospective registry, involving patients representative of “real life” DT during ICD implantation in France, reveals that although DT is still considered the standard of care at implantation [3], approximately 10% of patients do not undergo VF induction during routine first ICD implantation. Untested patients appear to have more comorbidities than tested patients; they also exhibit a worse outcome during follow-up, with a higher rate of hospitalizations and a 15% 1-year mortality versus 5% in tested patients, although death in untested patients was mainly related to heart failure with no significant difference for arrhythmic deaths. There were no life-threatening complications related to DT at implantation.

Although the rate of complications during ICD implantation is low, it is not negligible. Birnie et al. [8] reported ICD testing complications in 19,067 patients undergoing de novo implantation or device replacements in all 21 adult ICD Canadian centres from January 2000 to September 2006. There were 0.016% (3/19,067) DT-related deaths. The incidence of cerebrovascular accident or transient ischaemic attack was 0.026% (5/19,067). Other severe complications included prolonged resuscitation during ICD testing in 27 patients (0.14% incidence), with two patients having significant sequelae. In the present study, VF induction was not associated with an increased rate of complications at implantation and no deaths or severe complications occurred during testing, but it must be emphasized that the number of patients undergoing testing was more than 20 times lower than in the study by Birnie et al. [8].

There was no difference in mortality between the two groups during the first month, whereas mortality was significantly higher in untested patients during long-term follow-up (14.9% versus 4.9%; P <0.001), (Table 2). This is in agreement with previous retrospective studies, which reported that lack of testing at the time of ICD implantation was associated with higher mortality during follow-up. For example, Pires et al. [18] reported in a retrospective monocentre study the outcome of 835 patients according to the DT performed at implantation. In this study, 129 patients had real defibrillation threshold determinations, whereas 503 had limited defibrillation safety margin testing and the remaining 203 had no DT. During follow-up, the success rates of the first delivered shock for spontaneous VT/VF events were identical in the three groups (>90%) and the second shock terminated the remaining episodes in all three groups. Sudden-death-free-survival rates were similar in the three groups. The overall long-term survival rate was, however, significantly lower in the untested group compared with that in the DFT group or the safety-margin testing group (58% vs 74% and 69%, respectively; P <0.0005). The lack of ICD testing was an independent predictor of overall mortality in the multivariable analysis. In the present study, the differing cumulative survival rates of 95% in tested versus 85% in untested patients (P <0.001) mainly related to heart failure and not to arrhythmic deaths.

In this observational study, the main reason given by the implanting physician for not performing a VF induction was poor haemodynamic condition. Untested patients appeared to be sicker than tested patients, with a significantly lower LVEF, a wider QRS complex, a higher NYHA class and a higher incidence of cardiac resynchronization therapy implantation. This tendency not to test the more severe patients has also been reported by others [8, 9, 18]. In the study by Pires et al. [18], the reasons for not performing a defibrillation test were inadequate anticoagulation at implantation or known cavity thrombus in almost half of the patients (49.8%) and intraoperative hypotension requiring supporting therapy in around 20% of cases. In our study, the main reasons given for not performing DT were poor haemodynamic conditions with intraoperative hypotension in almost two-thirds of the patients and primary indication or lack of adequate anticoagulation for approximately 20% of the patients. These discrepancies may largely be explained by the difference in the period of inclusion, with implantations mainly due to secondary prevention in the study by Pires et al. [18] and mostly primary prevention indications in our study (approximately two-thirds of the patients). Although the conclusions of the Canadian experience are drawn from a registry with all the limitations of retrospective registries, Birnie et al. [8] reported that the decision not to perform a DT was not random, with a tendency not to test the sickest patients. Similar observations were reported in the recent Ontario ICD registry [9], with only 58% of patients undergoing a defibrillation test at first implantation or device replacement. In this registry, Healey et al. suggested that physicians have a bias against testing patients with an LVEF<20% and those with AF, who are at increased risk of embolic complications, particularly if AF is converted to sinus rhythm during testing. The present study, carried out in everyday medical practice during ICD implantation, was associated with a higher incidence of death during long-term follow-up of untested patients who appeared to be sicker than tested patients; these findings are in agreement with these previous statements.

Study limitations

Patients included in the present study were not consecutive, as the decision to include a patient receiving a de novo ICD was left to the investigator's discretion. In this prospective study, data were collected on paper and some missing data could not be obtained despite extensive repeated requests to the investigators.

Conclusion

From this large prospective study, it appears that more than 10% of ICD patients are implanted without DT. Untested patients appear to be sicker than tested patients with a more severe long-term outcome and no difference in mortality due to arrhythmic events. Prospective randomized trials with longer follow-up are mandatory to determine whether DT is still required and how it should be achieved, during ICD implantation.

Contributors

The following institutions and investigators participated in the LEADER registry. Co-Principal Investigators: Arnaud Lazarus, MD, Clinique Ambroise Paré, Neuilly, France; Nicolas Sadoul, Centre Hospitalier Universitaire, Nancy, France. Collaborating Investigators: Abbey Selim, MD, Gilles Lande, MD, Hervé Le Marec, MD, Vincent Probst, MD, Centre Hospitalier Universitaire, Nantes; Aït-Saïd Mina, Thomas Olivier, Clinique Ambroise Paré (1), Neuilly; Alonso Christine, Jauvert Gaël, Lazarus Arnaud, Ritter Philippe, Clinique Ambroise Paré (2), Neuilly; Anselme Frédéric, Savouré Arnaud, CHU Rouen; Babuty Dominique, Chenevez Patrick, Peycher Patrick, CHU Tours; Billon Olivier, CHD de La Roche sur Yon; Bizeau Olivier, CHR Orléans; Blanc Jean-Jacques, Mansourati Jacques, CHU Brest; Blangy Hugues, Sadoul Nicolas, CHU Nancy; Boveda Serge, Combes Nicolas, Goutner Christophe, Clinique Pasteur-Toulouse; Burban Marc, Cebron Jean Pierre, Gras Daniel, Nouvelles Cliniques Nantaises-Nantes; Camous Jean-Pierre, Raybaud Florence, CHU Nice; Canavy Isabelle, CHITS Font Pré-Toulon; Carlioz Roland, HIA St Anne-Toulon; Chapelet Alain, Couderc Philippe, Clinique Cardiologique Aressy; Cheggour Saïda, Faugier Jean-Paul, CH Avignon; Chenevez Patrick, Peycher Patrick, Clinique St Gatien-Tours; Chevalier Philippe, CHU Lyon; Comet Bertrand, Macaluso Gilles, Clinique Beauregard-Marseille; Copie Xavier, Lascault Gilles, Paziaud, Olivier, Piot Olivier, CCN-Saint-Denis; Crocq Christophe, Mabo Philippe, Pavin Dominique, CHU Rennes; Davy Jean-Marc, Pasquié Jean-Luc, Razcka Franck, CHU Montpellier; Defaye Pascal, CHU Grenoble; Deharo Jean-Claude, Djiane Pierre, Groupe Hospitalier de La Timone-CHU Marseille; Delarche Nicolas, CHG de Pau, Delay Marc, Duparc Alexandre, CHRU Toulouse; Dupuis Jean-Marc Victor Jacques, CHRU Angers; Mariottini Claude, Durand Philippe, CMC Institut Arnaud Tzanck-Nice; Hamdaoui Brahim, Poindron Damien, Elbaz Nathalie, CHU Créteil; Fareh Sami, Polyclinique de Rillieux la Pape; Flammang Daniel, CH Angoulême; Gartenlaub Olivier, Hôpital Girac-Nogent sur Marne; Frank Robert, Hôpital Pitié-Salpétrière-CHU Paris; Galley Daniel, CHG Albi; Clinique Pasteur: Guyomar Yves, CH St Philibert-Lomme; Leclercq Jean François, Halimi Franck, CMC Parly II- Le Chesnay; Hermida Jean-Sylvain, CHRU Amiens; Institut Jacques Cartier; Lagrange Anahita, CHRU Limoges; Sbragia Pascal, Trigano Alexandre, Hôpital Nord CHU Marseille; Scanu Patrice, CHRU Caen; Trancart Vincent, CHU de Pointe à Pitre, France.

Disclosure of interest

Nicolas Sadoul has received consulting honoraria and research grants from Boston Scientific, Medtronic and Sorin, and research grants from Biotronik and St. Jude Medical; Pascal Defaye has received consulting honoraria and research grants from Boston Scientific, Medtronic and Sorin; Olivier Bizeau has received consulting honoraria and research grants from Boston Scientific and St. Jude Medical, consulting honoraria from Biotronik and research grants from Medtronic; Jean-Marc Dupuis has received research grants from Boston Scientific; Hugues Blangy and Arnaud Lazarus have received research grants from Biotronik, Boston Scientific, Medtronic, St. Jude Medical and Sorin; Nicolas Delarche has received research grants from Boston Scientific, Medtronic, St. Jude Medical and Sorin; Jean-Jacques Blanc has received honoraria from Boston Scientific, Medtronic and St. Jude Medical; Elisabeth Mouton is an employee of Boston Scientific.


Acknowledgements

We thank Ms. Stephanie Gautier, who controlled the quality of the clinical data at Boston Scientific, and Mrs. Florence Mercier, biometrician, for her assistance and critical comments. This study was sponsored by Boston Scientific Corporation, Guidant France SAS.

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