Reduction of inappropriate anti-tachycardia pacing therapies and shocks by a novel suite of detection algorithms in heart failure patients with cardiac resynchronization therapy defibrillators: a historical comparison of a prospective database
Reduction of inappropriate anti-tachycardia pacing therapies and shocks by a novel suite of detection algorithms in heart failure patients with cardiac resynchronization therapy defibrillators: a historical comparison of a prospective database
Maurizio Lunati 3
Alessandro Proclemer 1
Giuseppe Boriani 0
Maurizio Landolina 6 7
Emanuela Locati 3
Roberto Rordorf 7
Elisabetta Daleffe 1
Renato Pietro Ricci 5
Domenico Catanzariti 4
Luca Tomasi 9
Michele Gulizia 8
Maria Stella Baccillieri 2
Giulio Molon 10
Maurizio Gasparini 11
0 University of Bologna and Azienda Ospedaliera S.Orsola-Malpighi , Bologna , Italy
1 S. Maria della Misericordia Hospital , Udine , Italy
2 Ospedale P. Cosma , Camposampiero , Italy
3 'A De Gasperis' Cardiac Department, Niguarda Ca' Granda Hospital , Piazza Ospedale Maggiore, 3, 20162 Milano , Italy
4 Santa Maria del Carmine Hospital , Rovereto , Italy
5 San Filippo Neri Hospital , Rome , Italy
6 Ospedale Maggiore , Crema (Cremona) , Italy
7 Fondazione Policlinico S. Matteo IRCCS , Pavia , Italy
8 Ospedale Garibaldi Nesima , Catania , Italy
9 Azienda Ospedaliera Universitaria Integrata , Verona , Italy
10 Ospedale Sacro Cuore Don Calabria , Negrar , Italy
11 IRCCS Istituto Clinico Humanitas , Rozzano , Italy
Aims Implantable cardioverter defibrillators improve survival of patients at risk for ventricular arrhythmias, but inappropriate shocks occur in up to 30% of patients and have been associated with worse quality of life and prognosis. In heart failure patients with cardiac resynchronization therapy defibrillators (CRT-Ds), we evaluated whether a new generation of detection and discrimination algorithms reduces inappropriate shocks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Methods We analysed 1983 Medtronic CRT-D patients (80% male, 67 + 10 years), 1368 with standard devices (Control CRTand results D) and 615 with new generation devices (New CRT-D). Expert electrophysiologists reviewed and classified the electrograms of all device-detected ventricular tachycardia/fibrillation episodes. Total follow-up was 3751 patients-years. Incidence of inappropriate shocks at 1 year was 2.8% [95% confidence interval (CI) ¼ 2.0 - 3.5] in Control CRT-D and 0.9% (CI ¼ 0.4 - 2.2) in New CRT-D (hazard ratio ¼ 0.37, CI ¼ 0.21 - 0.66, P , 0.001). In New CRT-D, inappropriate shocks were reduced by 77% [incidence rate ratio (IRR) ¼ 0.23, CI ¼ 0.16 - 0.35, P , 0.001] and inappropriate antitachycardia pacing by 81% (IRR ¼ 0.19, CI ¼ 0.11 - 0.335, P , 0.001). Annual rate per 100 patient-years for appropriate VF detections was 3.0 (CI ¼ 2.1 - 4.2) in New CRT-D and 3.2 (CI ¼ 2.1 - 5.0) in Control CRT-D (P ¼ 0.68), for syncope was 0.4 (CI ¼ 0.2 - 0.9) in New CRT-D and 0.7 (CI ¼ 0.5 - 1.0) in Control CRT-D (P ¼ 0.266), and for death was 1.0 (CI ¼ 0.6 - 1.6) in New CRT-D and 3.5 (CI ¼ 3.0 - 4.1) in Control CRT-D (P , 0.001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion Detection and discrimination algorithms used in new generation CRT-D significantly reduced inappropriate shocks when compared with standard CRT-D. This result, with no compromise on VF sensitivity or risk of syncope, has important implications for patients' quality of life and prognosis. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
† The clinical community is nowadays discussing about the best
strategies to avoid unnecessary and/or inappropriate ICD
† Strategies to reduce shocks comprise VT/VF detection
limited to only faster rhythms or to sustained durations and
programming of anti-tachycardia pacing to painlessly terminate
slow and fast VT.
† In our research, we demonstrated that combining a new
generation of arrhythmia discrimination algorithms and
evidence-based shock reduction programming results in a
significant reduction of inappropriate shocks, ATP, and
† Our data confirm and complete PainFREE SST results; in
particular, it characterizes the inappropriate shocks incidence in
the pure population of CRT-ICD and compares this
incidence with a historical population of patients with previous
CRT-ICDs, which did not exploit the new generation of
arrhythmia discrimination algorithms.
† These results, obtained with no compromise on VF detection
sensitivity or risk of syncope, have important prognostic
implications because reduction of inappropriate therapies has
been associated with improved survival and quality of life.
Implantable cardioverter defibrillators (ICDs) are indicated in the
treatment of patients at high risk of ventricular
tachycardia/fibrillation (VT/VF) for both primary and secondary prevention of sudden
cardiac death.1 Always ICD detection algorithms have favoured
sensitivity to accurately detect life-threatening arrhythmias, over
specificity. This historically resulted in inappropriate ICD therapies, i.e.
therapies delivered on rhythms that are not ventricular
tachyarrhythmias, in 8 – 40% of ICD patients.2,3 Inappropriate shocks have
been associated with multiple adverse effects, impaired quality of
life, worse prognosis, and increased mortality.2 – 4
Recently, the use of specific detection programming, such as long
detection times or high rate VT or VF detection windows, and the
use of anti-tachycardia pacing (ATP) to terminate rapid VTs have
been proposed to reduce unnecessary or inappropriate ICD
shock.5 – 10 Nevertheless, the incidence of inappropriate shocks 1
year after implant remains in the range of 2.6 – 3% even in the
experimental arms of recent trials, such as the ‘Long Detection’ arm of
Advance III9 and in the ‘High-Rate Therapy’ arm and in the ‘Delayed
Therapy’ arm of MADIT RIT.10
The objective of our research was to evaluate whether novel
sensing and discrimination features, SmartShockTM technology
(Medtronic Inc., Minneapolis, MN, USA), improve device
performance in the presence of lead failures, T wave oversensing,
supraventricular tachycardias (SVTs), and non-sustained VT. In particular,
we aimed to test whether these improved discrimination algorithms
reduce inappropriate ICD shocks when compared with previous
generation ICDs in patients with heart failure (HF), systolic
dysfunction, and cardiac dyssynchrony, wearing ICDs with cardiac
resynchronization therapy defibrillators (CRT-Ds) via biventricular
pacing. This cohort of patients is of particular interest because
CRT-D implant is increasing rapidly.11
The patients included in the present analysis were followed up in a
network of 80 Cardiology Centers, which participate in the Italian
ClinicalService project [Clinical Trial Registration Information: http://
clinicaltrials.gov/ct2/show/NCT01007474]. This is a national
cardiovascular data repository and medical care project that aimed at evaluating
and improving the use of implantable cardiac devices in Italian clinical
practice. The project was approved by each site’s Medical Ethics
Committee or Medical Director and conforms to the principles outlined in
the Declaration of Helsinki. Each patient provided informed consent
for data collection and analysis.
All patients received a biventricular triple-chamber CRT-D in
accordance with ICD and CRT guidelines:1,12 i.e. HF in New York Heart
Association (NYHA) class II, III, or IV, depressed ventricular function [left
ventricular ejection fraction (LVEF) ≤35%], and wide QRS complex
Project design and objectives
The project consists of a historical comparison of a prospective
database of 1983 Medtronic CRT-D patients: 615 patients with Protecta
CRT-D (Medtronic Inc.), which utilize novel sensing and discrimination
features (SmartShock technology), formed the new generation (New
CRT-D) cohort, whereas 1368 patients with previous generation
Medtronic CRT-D, not equipped with SmartShock technology, formed the
historical Control CRT-D cohort.
The main objective was to evaluate whether new detection and
discrimination algorithms reduce inappropriate detections, ATP, and
shocks when compared with algorithms in previous generation CRT-Ds.
Secondary objectives comprised the comparison of the New CRT-D
group with the Control CRT-D group in terms of appropriate detection,
therapies and shocks, syncope, and mortality.
An independent Episode Review Committee, composed by expert
electrophysiologists, reviewed all arrhythmic episodes detected by the
device as VT/VF, particularly the electrograms stored prior to VT/VF
detection, after detection, and after therapy or VT/VF termination. The
committee identified appropriate detections and inappropriate
detection mechanisms and classified ICD therapies as appropriate or
inappropriate in accordance with the detection classification.
Follow-up and data collection
All patients were followed for at least 6 months according to each
centre’s clinical practice through standard in-hospital visits. Device
interrogations and clinical evaluations were performed at each in-hospital visit.
Data collection included information about VT/VF and SVT episodes,
device programming, cardiovascular medications, and cardiovascular
Device programming and discrimination
Device detection and therapy parameters were programmed according
to each centre’s clinical practice.
In the Control CRT-D cohort, SVT discrimination utilized PR Logic.5,6
This algorithm includes three criteria: a criterion designed to identify
rapidly conducted atrial fibrillation (AF), atrial flutter, or atrial
tachycardia; a criterion to identify sinus tachycardia; and another 1:1 SVTs
criterion, designed to identify other 1:1 SVTs, in which atrial and ventricular
activation is roughly simultaneous. At least, two of these criteria were
programmed in 97% of the patients.
The New CRT-Ds were programmed taking advantage of the
SmartShock technology,13 which comprises four algorithms developed to
reduce inappropriate shocks: (i) the WaveletTM algorithm differentiates
VT from SVT on the basis of QRS morphology, (ii) T-wave
discrimination algorithm identifies T-wave oversensing, (iii) right ventricular
lead noise algorithm discriminates sensed rhythms that are due to
lead noise from those that are from VT/VF, and (iv) Confirmation +
algorithm identifies non-sustained VT which spontaneously terminate.
Safety of the New CRT-D algorithms has been already proven by
showing that SmartShock algorithms (i) did not delay detection of
induced VF 14; (ii) were associated with 98.8% relative sensitivity on
true spontaneous ventricular arrhythmias; and (iii) appropriately
withheld therapy in 98.6% episodes.15
New CRT-D and Control CRT-D had very similar programming in
terms of VF detection interval, which was between 290 and 330 ms in
95.1 and 94.6% of patients (P ¼ 0.929), respectively, and of fast
ventricular tachycardia (FVT) window which was programmed in 75.9 and 75.7%
of patients (P ¼ 0.995), respectively. Conversely, the VF number of
intervals to detect (NID) was different (P , 0.001) with most [401
(65.2%)] New CRT-D patients programmed with NID ¼ 18/24,
whereas Control CRT-D patients were programmed with NID ¼ 12/16 in
1096 (80.1%) cases and with NID ¼ 18/24 in 252 (18.4%) cases.
Another difference (P , 0.001) between New CRT-D and Control
CRT-D was that the VT window was programmed in 30.6 and 52.3%,
Continuous variables are reported as means and standard deviations or
medians and interquartile ranges, as appropriate. Categorical data are
reported as counts and percentage. The rate of events (number of
detections, ATP, shocks, syncopes, or deaths over time) was computed
per 100 person-years and reported separately for each group, together
with their 95% confidence intervals (CIs). Rates were compared by
means of either a mixed Poisson model or a negative binomial
regression model (if over-dispersion was present). Incident rate ratios
(IRRs) and CIs were used to compare the two groups. The analyses
of time-to-the-first event were described by means of Kaplan – Meier
curves and compared between the groups by means of the log-rank
test. Cox models were fitted and hazard ratios (HRs) with CI were
computed. The proportional hazard assumptions were tested by means of
Schoenfeld residuals. Multivariate analysis was used to identify
predictors of inappropriate shocks and to account for differences in the
baseline characteristics of New CRT-D and Control CRT-D patients.
Propensity score analysis16 was also used to compare event rates
between two subgroups of New CRT-D and Control CRT-D patients
having similar distributions of baseline characteristics. The baseline
variables that were considered in the multivariate analyses and in the
propensity score analyses were age, CRT-D implant indication, AF history,
hypertension, myocardial infarction, diabetes, AV block, left bundle
branch block, LVEF, and use of amiodarone, digitalis, and beta-blocking
All tests were two-sided and a two-tailed P-value of 0.05 was
considered statistically significant.
SAS 9.3 (SAS Institute Inc., Cary, NC, USA) was used for statistical
Patients’ baseline characteristics are shown in Table 1.
Median follow-up was 39 months (interquartile range ¼ 24 – 52
months) in Control CRT-D and 20 months (interquartile range ¼ 6–
48 months) in New CRT-D. Total follow-up was 3751 patients-years.
Inappropriate ICD shock incidence
The Kaplan – Meier incidence of inappropriate shocks was significantly
lower in New CRT-D, as shown in Figure 1; in particular, at 1 year it
was 0.9% (CI ¼ 0.4 – 2.2) in New CRT-D and 2.8% (CI ¼ 2.0 – 3.5) in
Control CRT-D [HR ¼ 0.37 (CI ¼ 0.21 – 0.66), P , 0.001].
Number, annual rate, and IRR of patients and episodes with
inappropriate shocks, comparing New CRT-D and Control CRT-D,
is shown in Table 2 for all-cause shocks and for the specific
mechanisms of inappropriate detections. In particular, inappropriate shocks
occurred in 14 New CRT-D (1 patient suffered inappropriate
shocks for two different causes) and 91 Control CRT-D patients
(5 patients suffered inappropriate shocks for two different causes).
Also, the total number of inappropriate shocks was significantly
reduced in New CRT-D patients compared with Control CRT-D
patients, with an annual rate of 2.1 (CI ¼ 1.5 – 2.9) and 9.1 (CI ¼
8.3 – 10.0) shocks per 100 patient-years [IRR ¼ 0.23 (CI ¼ 0.16 –
0.35), P , 0.001], respectively.
Predictors of inappropriate ICD shocks
At multivariable analysis, inappropriate shocks were significantly
associated with several patient characteristics such as wearing a new
generation CRT-D [IRR ¼ 0.10 (CI ¼ 0.04 – 0.25), P , 0.001], age
[IRR ¼ 0.98 (CI ¼ 0.96 – 0.99), P ¼ 0.030], AF [IRR ¼ 2.52 (CI ¼
1.67 – 3.80), P , 0.001], myocardial infarction [IRR ¼ 0.34 (CI ¼
0.21 – 0.54), P , 0.001], and left bundle branch block [IRR ¼ 4.18
(CI ¼ 2.10 – 8.32), P , 0.001].
Inappropriate ICD shock incidence
adjusted for baseline characteristics
The two CRT-D cohorts showed statistical differences in a few
baseline characteristics, as shown in Table 1; incidence of
inappropriate detections, ATP, and shocks, adjusted at multivariable analyses,
confirmed that New CRT-D patients had a lower risk of
inappropriate detections and therapies when compared with Control CRT-D
(Table 3). Propensity score analysis, performed to exclude that the
reduction of inappropriate shocks in the New CRT-D cohort was
due to the imbalance in baseline characteristics, identified two
homogeneous subgroups of 161 New CRT-D patients and 161
Control CRT-D patients and estimated an IRR of episodes with
inappropriate shocks equal to 0.38, i.e. 62% relative reduction,
associated with New CRT-D patients, with an adjusted P ¼ 0.044, and an
IRR of the total number of inappropriate shocks equal to 0.27, i.e.
73% relative reduction, associated with New CRT-D patients,
with an adjusted P ¼ 0.005.
Inappropriate ICD shock incidence
adjusted for ICD programming
A multivariable analysis, accounting for VT window programming
and considering only patients with NID ¼ 18/24, in order to
NYHA, New York Heart Association; LBBB, left bundle branch block; LVEF, left ventricular ejection fraction; LVEDV, left ventricular end-diastolic volume; LVESV, left ventricular
end-systolic volume; ACE, angiotensin-converting enzyme.
exclude the effect of NID programming differences in New CRT-D
vs. Control CRT-D, confirmed that New CRT-D patients had a
lower risk of inappropriate ATP and shocks when compared with
Control CRT-D (Table 4).
We observed no differences in the rates of appropriate VF
detections between New CRT-D and Control CRT-D patients [3.0
(CI ¼ 2.1 – 4.2) per 100 patient-years vs. 3.2 (CI ¼ 2.1 – 5.0) per
100 patient-years, IRR ¼ 0.92 (CI ¼ 0.62 – 1.36), P ¼ 0.68].
Conversely, when evaluating all appropriate ventricular tachyarrhythmia
detections, i.e. VF, FVT, and VT, we observed less detections and
therapies in the New CRT-D cohort compared with Control
CRT-D patients, in particular, the annual rate for detections was
4.2 (CI ¼ 3.1 – 5.8) per 100 patient-years in New CRT vs. 11.0
(CI ¼ 9.8 – 12.3) per 100 patient-years in Control CRT-D, IRR ¼
0.38 (CI ¼ 0.29 – 0.51) (P , 0.001), the annual rate for appropriate
ATP was 2.5 (CI ¼ 1.6 – 3.7) per 100 patient-years vs. 7.3 (CI ¼
6.3 – 8.3) per 100 patient-years, IRR ¼ 0.32 (CI ¼ 0.23 – 0.46)
(P , 0.001), and the annual rate for appropriate shock was 1.5
(CI ¼ 0.8 – 2.5) per 100 patient-years vs. 4.3 (CI ¼ 3.6 – 5.2) per
100 patient-years, IRR ¼ 0.32 (0.22 – 0.48) (P , 0.001).
A total of 7 syncopes in 9 patients were reported in the New
CRT-D arm and 32 in 36 patients in the Control CRT-D arm, among
which 0 and 2, respectively, were considered to be related to VT/VF
episodes or ICD treatment. The annual rate of syncope was similar
in the two compared groups [0.4 (CI ¼ 0.2 – 0.9) per 100
patientyears in New CRT-D patients and 0.7 (CI ¼ 0.5 – 1.0) in Control
CRT-D patients (IRR ¼ 0.63 (CI ¼ 0.28 – 1.42), P ¼ 0.266)]. Also
at propensity score analyses, the risk of syncope was similar in the
two groups (IRR ¼ 0.75, P ¼ 0.675).
The mortality rate was 1.0 (CI ¼ 0.6 – 1.6) per 100 patient-years
in the New CRT-D patients and 3.5 (CI ¼ 3.0 – 4.1) in the Control
CRT-D patients. At multivariate analyses, AT/AF history and
Control CRT-D cohort resulted associated with mortality.
ICDs have been established to be the most effective therapy in the
prevention and treatment of sudden cardiac death.1 Despite efforts
to improve ICD technology and detection algorithms, a significant
number of episodes are still inappropriately treated.2,3
Inappropriate shocks have been associated with impaired quality of life,
psychological distress, reduction of battery life, and worse
prognosis.2 – 4 The proportion of subjects with inappropriate shocks at
1 year in clinical practice is 3 – 4%.2,3,6,7,9,10 These findings outline
the need for enhanced shock reduction strategies.
Main research findings
Detection and discrimination algorithms in a new generation of
CRT-Ds significantly reduced inappropriate detections and
Figure 1 Kaplan – Meier incidence of inappropriate ICD shocks
in the New CRT-D and Control CRT-D patients’ cohorts.
therapies and in particular inappropriate shocks when compared
with the historical physician-tailored Control CRT-D cohort.
Therefore, our research confirmed the clinical benefit of combining
a new generation of arrhythmia discrimination algorithms
and evidence-based shock reduction programming; such VT/VF
detection limited to only faster rhythms or to sustained durations
and programming of ATP to painlessly terminate slow and
Inappropriate shock prevention in new
The percentage of patients with inappropriate shocks at 1 year was
0.9% in the New CRT-D cohort (Figure 1), which favourably
compares with the findings of the PainFREE observational study,15 which
tested the same discrimination algorithms on 1071 Protecta
CRT-ICD patients and 948 dual-chamber ICD patients and found
a 1-year inappropriate ICD shock incidence equal to 1.5%.
Importantly, the 2.8% 1-year incidence of inappropriate ICD
shocks estimated in our Control CRT-D cohort represents a
state-of-the-art outcome, being similar to the results obtained in
the study arms of two recent randomized trials,9,10 with detection
and treatment programming specifically devoted to inappropriate
shock reduction; inappropriate ICD shock incidence at 1 year was
2.6% in the Long Detection arm of ADVANCE III study9 and 3%
in the High-Rate Therapy arm and in the Delayed Therapy arm of
MADIT RIT study.10 The comparison of inappropriate shock
incidences in our New CRT-D cohort and in the ADVANCE III and
MADIT RIT trials suggests that in new generation ICDs, the novel
discrimination algorithms may avoid inappropriate shocks in 2 of 3
patients every 100 patients.
Importantly, beyond the reduction of patients with inappropriate
shocks, the novel algorithms yielded a 66% reduction of episodes
with inappropriate shocks and a 60% reduction in the number of
shocks (Table 2, last 2 rows).
It is worthwhile to outline that our research represents real life
and included all-comers CRT-D patients, whereas often
randomized clinical trials have strict eligibility criteria; for example, AF
history was present in 31% of the patients in our research and only in
10% of ADVANCE III9 and MADIT RIT10 trials, and AF is known as
the most frequent cause of inappropriate shocks.2,3,4,17
Out of the 91 Control CRT-D patients who suffered
inappropriate shocks, AF was the cause of inappropriate detection in 54 (59%)
patients and in 132/253 (52%) episodes with inappropriate shocks.
Despite AF history was more frequent (41.5%) in New CRT-D
patients compared with Control CRT-D patients (26.7%, P , 0.001),
inappropriate shocks due to AF in New CRT-D were significantly
less, with a reduction of 62% shocked patients and 77% shocked
episodes (Table 2). In the studied new generation CRT-D, a QRS
morphology analysis algorithm, which uses the wavelet
decomposition of electrogram signals to compare the morphology of
tachycardia complexes with a previously collected normal sinus rhythm
template, has been associated with significant reduction of
inappropriate therapies for SVT.18
Finally, multivariable analysis confirmed the efficacy of the new or
improved detection and discrimination algorithms featured in new
generation of CRT-D by showing that these devices were associated
with a significantly lower risk of inappropriate shocks [IRR ¼ 0.10
(CI ¼ 0.04 – 0.25), P , 0.001].
New CRT-D and Control CRT-D cohorts did not differ as for
appropriate VF detection rates and syncopes. This observation,
together with previous findings,14,15 is reassuring as it suggests that
optimization of inappropriate detection algorithms was obtained
with no compromise in terms of VF sensitivity or risk of syncopes.
New CRT-Ds were also associated with lower rates of
appropriate detections and therapies for FVT/VT episodes. This could be
explained by differences in the compared patients’ cohorts and by
differences in device programming for VT and FVT detection and
therapies. In particular, the longer NIDs programmed in New
CRT-D compared with Control CRT-D likely resulted in a
reduction of unnecessary detection and therapies.
The finding of a low mortality rate in New CRT-D patients should
be regarded with caution, given the observational nature of our
research. A recent meta-analysis,19 considering four randomized
trials6,9,10,20 and two observational studies,7,8 has shown that
therapy reduction programming, based on prolonging the time required
to detect a sustained ventricular arrhythmia, resulted in a large,
significant, and consistent reduction in mortality. The huge reduction
of inappropriate therapies and of unnecessary therapies on
appropriate detections found in New CRT-D patients could have
contributed, together with other factors, to the observed low mortality.
In the last 15 years, clinical and technological research has been
particularly focused on reducing unnecessary and inappropriate ICD
shocks.2,5 – 10,13 – 15,18,20 First, ATPs have been proposed in the
PainFREE studies2,5 to avoid unnecessary shocks; secondly, strategic
programming has been tested in clinical practice both in
observational and in randomized studies6 – 8; finally, delayed detection,
permitting non-sustained and slower arrhythmias to self-terminate, has
been shown to be safe and effective in reducing both unnecessary
and inappropriate shocks.9,10 Recently, the PROVIDE study20 has
shown that a combination of programmed parameters utilizing
high detection rates, long detection intervals, empiric ATP, and
optimized SVT discriminators reduces ICD therapies without
increasing arrhythmic syncope and is associated with reduction in all-cause
mortality. Now our research shows the synergistic effect of
state-of-the-art ICD programming and novel detection algorithms.
Therefore, we suggest that specific detection programming, such
as longer detection times or shorter VT/VF detection windows, as
those proposed by recent trials,9,10 may provide even better
inappropriate shock prevention when applied on top of optimal
detection and discrimination capabilities as those studied in our
research. Improved detection capabilities have the advantage that
can be applied in all patients, whereas specific programming settings,
such as VT and VF detection windows, should be programmed on
the basis of patients’ characteristics; indeed, the benefit of
eliminating a slow VT detection zone in order to reduce the probability of
inappropriate therapies should be balanced against the risk of failing
to treat VT. Minimization of ICD inappropriate shocks does clear
the way for more patients to benefit from ICD life-saving
The major limitation of our clinical research is that, deriving from a
project aiming observation of device use in standard clinical practice,
it has an observational non-randomized design. Besides, the
limitations of multicentre observational studies, such as potential bias in
patient selection or patient treatment, apply to our research.
Indeed, the differences in baseline characteristics and device
programming between the two compared groups were considerable.
However, we believe that the acknowledged limitations were
mitigated by the fact that data were collected prospectively, the
research endpoints were prespecified, the analysis plan was designed
before the data set was opened, and finally both multivariable and
propensity score analyses were performed to account for patients
characteristic and device programming differences in the two
research arms. These methods allowed us also to verify that lead
type, in particular Sprint Fidelis, which historically has been
associated with higher incidence of inappropriate shocks, among other
variables, did not impact findings of the presented research.
Although primary endpoint, being derived from device
diagnostics, was not affected by data collection limitations, we cannot
exclude underreporting in syncopes and deaths.
Due to the data collection and reporting platform, all used ICDs
were Medtronic systems; this may limit a general applicability of
Improved detection and discrimination algorithms significantly
reduced incidences and annual rates of inappropriate shocks, ATP,
and detections when compared with algorithms used in a standard
CRT-D. This result, obtained with no compromise on VF detection
sensitivity or risk of syncope, has important prognostic implications
because reduction of inappropriate therapies has been associated
with improved survival.19
The authors thank Andrea Grammatico and Silvia Bisetti for
scientific advice and Lorenza Mangoni and Paola Di Stefano for statistical
Conflict of interest: M.L. received modest consultancy and
speaker’s fees from Medtronic, St Jude Medical, Sorin, Boston Scientific,
and Biotronik. G.B. has minor consultancy fees from Boston
Scientific and Medtronic. M.L. received modest speaker fees from
Medtronic and St Jude Medical and an advisory board relationship
with Medtronic and St Jude Medical. R.P.R. has minor consultancy
fees from Biotronik and Medtronic. G.M. has consultancy and
speaker’s fees from Boston, St Jude Medical, and Medtronic. The other
authors have no relationship to disclose with regard to the present
This research was performed within the framework of the Italian
ClinicalServicew project, a national cardiovascular data repository and
medical care project funded by Medtronic Italia, an affiliate of Medtronic Inc.
No other funding sources were involved in the research. The authors
are responsible for the design and conduct of this research.
1. Zipes DP , Camm AJ , Borggrefe M , Buxton AE , Chaitman B , Fromer M et al. ACC/ AHA/ ESC 2006 Guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death-executive summary: a report of the American College of Cardiology/American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines Developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society . Eur Heart J 2006 ; 27 : 2099 - 140 .
2. Sweeney MO , Wathen MS , Volosin K , Abdalla I , DeGroot PJ , Otterness MF et al. Appropriate and inappropriate ventricular therapies, quality of life, and mortality among primary and secondary prevention implantable cardioverter defibrillator patients: results from the Pacing Fast VT REduces Shock ThErapies (PainFREE Rx II) trial . Circulation 2005 ; 111 : 2898 - 05 .
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