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.
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 ± 13,5 ans ; 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.
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) . Today, DFT determination is rarely performed, but a ≥ 10 J safety margin for efficient defibrillation is required . DFT determination is, however, still considered as a critical part of a successful implantation procedure, even though Swerdlow et al. 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 , 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%) . 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 ; changes in ICD technology resulting in lower DFTs ; 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 . There is an increasing body of literature on the outcome of patients implanted without DT . 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 .
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).
| Total ( n = 904) | VF induction group ( n = 810) | Untested group ( n = 94) | P a | |
|---|---|---|---|---|
| Men | 85.4 | 85.8 | 81.9 | 0.35 |
| Age (years) | 62.1 ± 12.8 | 61.7 ± 12.8 | 65.4 ± 11.6 | <0.01 |
| LVEF (%) | 0.32 ± 0.13 | 0.32 ± 0.13 | 0.26 ± 0.08 | <0.001 |
| NYHA class III + IV | 45.7 | 42.5 | 73.1 | <0.001 |
| QRS complex (ms) | 127.6 ± 38.0 | 125.4 ± 37.5 | 146.2 ± 37.5 | <0.001 |
| Cardiomyopathy | ||||
| Ischaemic | 562 (62.2) | 503 (62.1) | 59 (62.8) | 1.000 |
| Dilated | 232 (25.7) | 199 (24.6) | 33 (35.1) | 0.033 |
| Other disorders | 91 (10.1) | 89 (11.0) | 2 (2.1) | <0.01 |
| None | 19 (2.1) | 19 (2.3) | 0 (0) | 0.25 |
| Permanent AF | 90 (10) | 74 (9.2) | 16 (17.4) | 0.026 |
| Primary prevention | 560 (62) | 486 (60) | 74 (79.6) | <0.001 |
| Devices | ||||
| VVI | 261 (28.6) | 244 (30.1) | 13 (13.4) | <0.001 |
| DDD | 230 (25) | 215 (26.1) | 15 (15.5) | 0.025 |
| CRT-D | ||||
| Total | 429 (47) | 360 (43.7) | 69 (71.1) | <0.001 |
| High energy only | 97 (10.5) | 73 (8.9) | 24 (24.7) | 0.029 |
| Drug therapy | ||||
| Beta-blocker | 664 (73.5) | 604 (74.6) | 60 (63.8) | 0.035 |
| Amiodarone | 246 (27.2) | 218 (26.9) | 28 (29.8) | 0.54 |
| ACE inhibitor/ARB | 642 (71.0) | 570 (70.4) | 72 (76.6) | 0.23 |
| Antiplatelet agent | 394 (43.6) | 354 (43.7) | 40 (42.6) | 0.91 |
| Anticoagulant | 261 (28.9) | 234 (28.9) | 27 (28.7) | 1.00 |
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